Foreward

Animal production in Australia is a significant contributor to the economy and a major employer of rural and regional Australians. We are fortunate to be free from most major diseases of livestock that impede production, affect trade and cause serious animal welfare concerns. Historically, this can be attributed in part to the distance and limited movements of animals, animal products and people from other major livestock producing regions.

This no longer is the case. International movement of passengers, mail and cargo are increasing and the threats of an incursion are becoming more prominent. For instance, in 2015-16 there were over 20 million international travellers, 42 million consignments of cargo and 158 million international mail items coming into the country.

Freedom from emergency animal diseases offers a distinct market advantage for exports of Australian animals and animal products. Estimates from 2015 suggest that, on average, freedom from foot-and-mouth disease and highly pathogenic avian influenza provide up to $13,172 and $6,000 annual profit for broadacre livestock and poultry producers, respectively.

The chapters in this book are written by some of the foremost experts in their field and provide the information veterinarians need to help them with the early detection, diagnosis and control of exotic and emerging infectious diseases in livestock.

Dr Beth Cookson
Australian Chief Veterinary Officer
Department of Agriculture, Fisheries and Forestry

Trevor Drew
Director, Australian Centre for Disease Preparedness
CSIRO

Preface

Outbreaks of emergency animal diseases (EADs) in Australia have the potential to cause significant socio-economic impacts, and affect animal, human and environmental health. Many of these diseases are exotic to Australia.

New diseases of animals continue to emerge and with this trend likely to continue it is important that veterinarians are prepared to investigate any unusual outbreaks of disease in domestic animals.

This field guide provides field veterinarians with readily accessible information on EADs. It will help those in the field include appropriate EADs in their differential diagnoses, and take appropriate action if presented with signs of an unusual disease.

Early and accurate diagnosis of any case of an EAD is essential for effective control, since controlling localised disease is more effective than managing widespread disease.

Exclusion testing of EADs conducted on suspect case investigations increases the likelihood of early detection of any EAD events in Australia. All negative laboratory test results generated through this process provide data that support Australia’s claims of freedom from EADs for international market access purposes.

This field guide does not provide exhaustive information on each disease, focusing instead on information that veterinarians need when confronted with disease situations in the field. It is not a textbook, and we refer readers to more comprehensive sources at the end of each disease chapter. Likewise, the discussion of laboratory procedures is limited to information that helps with collecting and submitting useful diagnostic samples.

This field guide covers high priority syndromes and diseases of domestic terrestrial animals. It is intended that further syndromes and disease chapters will be added over time. It complements the Australian Veterinary Emergency Plan (AUSVETPLAN), Australia’s coordinated national response plan for controlling and eradicating EADs.

Other materials are available to assist disease recognition and investigation in aquatic animals, and in wildlife. The Australian Government Department of Agriculture, Forestry and Fisheries has published Aquatic Animal Diseases Significant to Australia: Identification Field Guide 4th Edition. The Wildlife Health Australia website also includes resources to support investigation of wildlife diseases.

Acronyms and abbreviations

TermDefinition
ACDPAustralian Centre for Disease Preparedness
AFIPArmed Forces Institute of Pathology
AHSAfrican horse sickness
AIAvian influenza
ASFAfrican swine fever
BSEBovine spongiform encephalopathy
CFSPHThe Center for Food Security and Public Health
CSFClassical swine fever
EADEmergency animal disease
EuFMDEuropean commission for the control of foot-and-mouth disease
FMDFoot-and-mouth disease
EHDEpizootic haemorrhagic disease
EIEquine influenza
HPAIHighly pathogenic avian influenza
LPAILow pathogenic avian influenza
LSDLumpy skin disease
OIEWorld Organisation for Animal Health
PEDPorcine epidemic diarrhoea
PIADCPlum Island Animal Disease Center
PPRPeste des petits ruminants
PrPProtease resistant protein
PRRSPorcine reproductive and respiratory syndrome
RVFRift Valley fever
SVDSwine vesicular disease
TGETransmissible gastroenteritis
USDAUnited States Department of Agriculture, Forestry and Fisheries
vCJDvariant Creutzfeldt-Jakob disease
VSVesicular stomatitis
WAHISWorld Animal Health Information System

1. General information

1.1 Roles and responsibilities of field veterinarians in emergency animal disease detection and reporting

Australia’s animal health system relies on veterinarians reporting any suspicion of an emergency animal disease (EAD).

EADs are diseases that have been agreed by governments and industry in Australia as capable of having severe effects on trade, production, the environment, and/or human health. Most are diseases exotic to Australia but some are endemic diseases such as Hendra virus infection and anthrax. Others are described as ‘emerging diseases’ because increasing incidence and/or an expanding geographic or host range would result in them having greater trade or public health effects.

It is important that veterinarians know about EADs for several reasons.

  • Early detection and reporting helps prevent the establishment of exotic diseases, or the spread of serious endemic diseases, some with human health implications.
  • Investigating any suspected EAD generates evidence that helps support Australia’s animal health status claims.
  • Veterinarians have legal and professional requirements to report any suspected EAD.

When to suspect an emergency animal disease

There is a large list of (in some cases, unfamiliar) notifiable animal diseases that veterinarians must report to the government authorities in each state and territory of Australia. All EADs are notifiable animal diseases in all states and territories nationally.

Broadly, you might suspect EADs in cases where:

  • there are abnormal mortality rates (in any species, including birds)
  • there are abnormal morbidity rates in animals (including birds)
  • there is rapid spread of disease through a herd or flock
  • the disease event affects multiple species
  • cloven-hooved animals have ulcers, erosions or blisters around the feet, muzzle, udder or teats and/or in the mouth
  • cloven-hooved animals are lame and drooling or salivating excessively
  • affected animals display unusual nervous signs (or progressing nervous signs)
  • there are multiple, deep, fly-struck wounds (particularly if this occurs in northern Australia)
  • there is a sudden, sharp and inexplicable fall in production
  • there are unusual and concerning clinical signs of disease in animals or birds
  • the clinical presentation suggests signs of a particular EAD, including those listed in Section 3.

How to report an emergency animal disease

If you suspect an EAD, phone government animal health authorities immediately from the affected property.

This is the most important step, because effective disease control relies on early detection.

Call the Emergency Animal Disease Hotline on 1800 675 888 to report the suspected EAD. Government duty veterinarians monitor the hotline and are available to advise you 24 hours a day, 7 days a week.

Alternatively, notify a state or territory government veterinary officer of the suspected EAD directly.

Leaving messages is inadequate. Avoid relying on other people to make the notification.

If you are unable to make a telephone call from the affected property, you should disinfect yourself and your vehicle (as thoroughly as possible in the circumstances) and travel to the nearest site where you can make the call. Ensure you do not enter premises with susceptible animals.

What information to include in a report

You will need to include this basic information in the initial telephone notification:

  • the types and approximate numbers of animals on the property (including feral animals) and which species are affected
  • a brief description of clinical signs of disease and gross lesions observed
  • the disease or diseases suspected
  • the name of the owner and/or farm manager
  • the full address and telephone number for the property
  • the date when the disease was first noticed, approximate numbers of sick and dead animals
  • whether any susceptible animals have recently left or been brought onto the property

This information allows animal health authorities to make the initial disease control and epidemiological tracing to begin.

You should remain on the property until a government veterinary officer arrives unless otherwise advised. Use this time to implement biosecurity measures to prevent further spread of infection, gather a comprehensive clinical history and epidemiological data on the outbreak from the livestock owner or workers.

Who should take samples and conduct a disease investigation?

Although this book provides general guidance, you should seek advice before sampling and conducting a disease investigation.

This is the decision of the state or territory Chief Veterinary Officer (CVO) or their delegate. It will depend on the circumstances. For example, in cases where there is a high suspicion of an EAD, the CVO would be expected to send a diagnostic team to investigate the outbreak and collect diagnostic samples.

This will ensure that risks to human and animal health of highly infectious diseases are managed appropriately, and investigations are undertaken effectively.

1.2 Safety, personal protection and containment of infection

Biosecurity for personal protection and infection containment

When you suspect an EAD, you need to use routine biosecurity procedures to:

  • contain infection to prevent the spread of infectious animal diseases between groups of animals on the property and to animals on other properties
  • prevent exposure of veterinarians and other people (including clients, clinic staff, couriers and laboratory staff) to potential zoonotic agents. Each state and territory identifies the prevention of exposure in occupational health and safety legal requirements.

Containment of infection

Containing the infection is of prime concern and you should gain the property owner’s cooperation to:

  • secure potentially-infected animals in well-fenced paddocks, yards, buildings, pens or cages, and prevent contact with unaffected herds or flocks of animals
  • confine animals as well as potentially-infected livestock products and fomites to the property
  • move livestock away from farm borders, particularly in the case of suspected diseases for which the causal organism can be airborne over considerable distances (e.g. foot-and-mouth disease)
  • avoid actions that would encourage the dispersal of feral animals from the property
  • dissuade people who have had recent contact with livestock from leaving the property
  • discourage unnecessary visitors from entering the property.

Advise any persons on the property to contact a government veterinary officer for instructions on personal disinfection (for containment purposes) before leaving the property.

Investigating a suspected zoonosis

Several animal diseases have serious public health implications. Examples are Hendra virus infection, rabies and Rift Valley fever. In investigating such diseases, you may need extra precautions to prevent infection of personnel by ingestion, inhalation of infected aerosols, or contamination of mucous membranes or abraded skin.

You may need to wear face masks, eye protection and standard protective clothing depending on the suspected disease. This is discussed in the appropriate chapter on each disease.

Adequate restraint and safe handling of live animals and carcasses is of critical importance, especially where diseases such as rabies are suspected as animals may become aggressive or unpredictable. In addition, when investigating a suspected zoonosis, personal hygiene and disinfection, as well as decontamination of post-mortem sites, must be of the highest standard.

Advise the client, the farm owner or manager and in-contact family members, farm employees and visitors of the steps they need to take to avoid infection. This should include advice on the safety of consumption of farm products.

1.3 General principles of disease investigation

The material in this section only provides general information on conducting a disease investigation. Seek advice from government veterinary services when you suspect an EAD.

A routine process for disease investigation involves assembling evidence and should include (click on the links for relevant sections):

Routine disease investigation biosecurity procedures

Routine disease investigation biosecurity procedures include:

Pre-visit preparation

Equip your vehicle with (in easily accessible containers with fitted lids):

  • personal protective equipment
  • extra clothing (boots and overalls)
  • cleaning (disinfection and decontamination) gear (including plastic bags)
  • equipment for restraint and humane destruction of animals
  • post-mortem instruments
  • instruments, containers and media for collection and transport of diagnostic specimens
  • telephone numbers and stationery.

The level of zoonotic disease risk and disease transmission risk presented by different animal disease investigation situations varies considerably. Therefore, it is fitting that you take a risk-based approach to manage the likelihood and consequences of either exposure to potential zoonotic infectious agents or the spread of infectious agents between sites.

Ensure risk management is commensurate to the level of risk posed. Veterinarians should:

  • use the minimum standard of personal protective equipment and biosecurity practices for any disease investigation
  • use an enhanced level of personal protective equipment and biosecurity practices where there is greater risk, such as when
    • exposure to a zoonotic pathogen during a disease investigation is plausible
    • the situation suggests that the disease agent may be highly transferable via fomites
  • use the highest level of personal protective equipment and biosecurity practices when the risk is highest, that is, potentially life-threatening zoonoses are involved. Examples would be suspected cases of Hendra virus infection, Australian bat lyssavirus infection or highly pathogenic avian influenza. Veterinarians need to keep abreast of the current guidelines and procedures for handling such cases.

It is suggested that veterinarians use a checklist (see an example in Appendix B) of equipment for disease investigation. Veterinary vehicles should carry supplies for both high- and low-risk activities.

Entry and exit procedures

In line with the principles of the perceived level of risk, practitioners should determine for each visit what entry and exit procedures are required.

Low biosecurity risk sites

For routine, low biosecurity risk site visits, standard procedures might include:

  • wearing clean overalls (regular or disposable)
  • wearing new, clean boots and/or washing footwear before entry
  • using clean instruments and equipment (in clean containers)
  • wearing gloves prior to handling animals or carcasses
  • wearing coverall clothing and protective footwear
  • maintaining hygienic processes when handling biological samples
  • safely packing biological samples
  • removing, bagging and disposing of used gloves, disposable overalls and other wastes before exiting the property
  • cleaning instruments in soapy water
  • cleaning boots thoroughly (grooves in the soles and the outside) prior to exiting the property
  • removing and bagging any dirty garments (such as overalls) prior to exiting the property
  • washing hands prior to exiting the property
  • cleaning and disinfecting clothes and equipment, replacing materials and disposing of contaminated waste in a biosecure way.
Higher biosecurity risk sites

For higher risk visits where there is a greater suspicion of (or likelihood of) disease spread, veterinarians should follow more thorough entry and exit procedures, and adopt more stringent personal hygiene and PPE measures. It is the practitioner’s responsibility to align these to disease specific procedures and the situation presented.

It is useful to have these processes detailed in clinic standard operating procedures that are carried in the vehicle. Ensure the equipment needed to follow these steps is packed in the vehicle at all times, as you will not always receive warning of when you will require them.

Figure 1.3.1
Figure 1.3.1 is a diagrammatic representation of a proposed entry and exit decontamination site suitable for higher risk visits. Figure adapted from Guidelines for veterinarians handling potential Hendra virus infection in horses Version 5.1 (2010) published by Biosecurity Queensland

When attending cases where the zoonotic and/or infectious risk has been assessed as high, veterinarians must wear full personal protective equipment during clinical examination and post-mortem examination. This may include the use of P2 or P3 masks, eye protection, double disposable gloves and involve strict protocols.

This includes situations where there is a suspicion of a significant zoonotic agent (e.g. Hendra virus infection, highly pathogenic avian influenza, anthrax, rabies lyssavirus infection, bat lyssavirus infection, Rift Valley fever, Nipah virus infection and transmissible spongiform encephalopathies).

When attending sites with a high biosecurity risk, follow a checklist (see Table 1.3.1 for an example) to implement high-level biosecurity protection.

Table 1.3.1 and Table 1.3.2 provide checklists for biosecurity entry and exit procedures.

High biosecurity risk site visit checklist
Table 1.3.1 Checklist for biosecurity entry procedures

Park your vehicle at a distance from livestock handling areas. to minimise the possibility that your vehicle will become contaminated.

Leave your watch and all jewellery items in the vehicle.

Retrieve all items required for the disease investigation from the car so you do not have to return.

Identify clean, dirty and transition zones between your vehicle and the livestock handling area (Figure 1.3.1).

Set up decontamination equipment in the transition zone and lay out a ground sheet.

In the transition zone, place:

  • a bucket of disinfectant for a footbath
  • a second bucket or spray bottle of disinfectant
  • scrubbing brush
  • two plastic bags with ties for waste.

In the clean zone, place:

  • a bucket or spray bottle of disinfectant
  • two plastic bags with ties for personal protective equipment disposal.

Put on personal protective equipment while in clean zone, being sure to:

  • wash hands with soap and dry
  • put on impermeable overalls with legs outside boots
  • put on a respirator (if required) and check the fit
  • put on eye protection, ensuring it fits snugly over respirator
  • put on two pairs of gloves (double gloved) with the outer pair fitting snugly over overall sleeves.
  • secure the outer glove onto the sleeves of impermeable overalls with tape over gloves onto sleeves.

The outer packing of specimen transport containers should not be taken into the dirty zone.

Enter the dirty zone. While on the property, select suitable areas for ante-mortem and post-mortem examination of animals. Conduct examination, sampling or post-mortem, and:

  • double bag samples
  • wipe each packing layer with disinfectant.
Table 1.3.2 Biosecurity exit procedures

At the completion of examinations (clinical or post-mortem) and collection of diagnostic specimens:

  • make arrangements for the safe disposal of carcasses
  • make arrangements to dispose any contaminated objects that are no longer required. These materials may be left on site for subsequent destruction if they cannot be moved safely
  • clean the ground or other surfaces (including instruments) contaminated by blood, excretions or tissues as thoroughly as possible and disinfect.

While still in the dirty zone:

  • remove gross contamination and use a hose or tub of water and soap/detergent to clean boots, overalls, gloves and instruments/equipment
  • immerse instruments/equipment in an appropriate concentration of disinfectant solution for at least 10 minutes (or leave behind for subsequent disinfection by a specialised team).

Return to the transition zone and:

  • put waste in a plastic bag, disinfect it, put it in a second bag and disinfect again, then place in clean zone
  • disinfect boots and wash or spray hands, equipment and samples with appropriate disinfectant
  • wash hands, face and other exposed skin surfaces with soap and water. Your nose should be blown several times into disposable tissues.

Once in the clean zone:

  • remove outer gloves and wash or spray inner gloves with disinfectant
  • remove overalls and boots, remove eye protection, then remove respirator once any dust has settled
  • put personal protective equipment in a plastic bag
  • remove inner gloves, put in plastic bag with other personal protective equipment and close securely
  • disinfect plastic bag then put in second plastic bag and disinfect again
  • wash hands with soap and dry hands thoroughly.

Assembling the evidence for diagnosis

Taking a case history

Taking a careful history of the events that have occurred, formulating a case definition to clarify precisely what is being investigated, and doing some basic epidemiology are important components of a disease investigation.

Taking a history requires the collection of accurate, quality information. Preparing a standard history collection template can help with gathering evidence (see an example in Appendix A).

Clinical investigation

Several specific guidelines for veterinarians performing clinical livestock disease investigations are to:

  • use personal protective equipment appropriate to the situation
  • begin investigation with the least affected groups of animals
  • clinically examine representative numbers of clinically affected and unaffected animals
  • determine a working case definition
  • take samples from an the appropriate number of animals for laboratory testing, based on advice from government veterinary officers
  • consider taking samples from affected and unaffected animals where pertinent
  • take an appropriate range of samples
  • always take body temperatures (remember that pyrexia is a key finding in many EADs)
  • ensure the proper restraint of animals, which is necessary both for personal safety and to ensure that a comprehensive examination of individuals can be done.
Selection of animals for clinical examination

It is important to select animals that are fully representative of the disease syndrome in the affected herd or flock. Where possible:

  • collect diagnostic samples from several animals
  • collect samples from animals early in the clinical course (not only are the causal organisms usually found in greatest concentration in tissues at this time, but secondary infections, which may mask the underlying cause, are less likely to be present)
  • collect specimens from animals that are freshly dead (most viruses and bacteria are quickly inactivated after the death of the host as autolysis of tissues occurs, particularly in hot weather) or slaughter sick animals for the purpose.

In some cases it may be desirable to deliver live sick animals to the laboratory (e.g. poultry). However, this must only be done after advice from the government veterinary officer and/or laboratory, who will take into account the microbiological security of such action and the physical security of the animals while being transported.

Case definitions

You can develop a working case definition following the history taking process and clinical examination. The benefit of having a case definition is that it helps to define whether there is a single disease or multiple problems occurring at the same time.

A case definition may need to be flexible to prevent excluding cases that are related, and can be altered over time if more information comes to light. This is helpful in providing clarity in determining the nature of unfolding disease events.

Basic epidemiological analysis

A distribution map, which shows the location and distribution of the livestock affected on a property (in relation to the location of all the livestock), plus paddocks and water bodies, may help suggest a possible cause of the problem. This may be hand drawn.

In addition, it is good practice in field investigations for veterinarians to use basic epidemiological measurements to determine fundamental event descriptors such as prevalence, incidence and mortality rates.

Prevalence is the proportion of a population affected by a disease at a given point in time. The prevalence is the number of affected animals divided by the total number of animals at risk.

Incidence is a measure of new cases of disease in a population within a defined time period. The cumulative incidence is the number of animals developing disease over the period in question divided by the number of non-diseased animals at the start of the period.

Mortality is the number of dead animals divided by the total number of animals in the population at the start of the period.

Other factors may also influence the expression of disease, including species, age, sex, reproductive status or other management activities. Comparing the prevalence, incidence or mortality in particular classes of animals can indicate factors associated with expression of disease.

It may also be useful to draw a timeline which shows the number of cases occurring over time and events considered potentially related to the problem. Similarly, a plotted graph of number of cases over time (an epidemic curve) is useful to visualise the timeframe of the outbreak or disease event. The pattern of the graph can indicate whether cases have the appearance of a ‘point source’ problem (such as a single access to a toxin) or a ‘propagating epidemic’ (indicating a possible infectious disease occurrence).

Post-mortem examination

Undertake post-mortems only where it is safe to do so. You should not conduct post-mortems for sudden death of livestock in the field due to the possibility of anthrax.

Post-mortem examinations should be carried out in a systematic way to ensure nothing is missed. This routine approach also leads to the most efficient use of time.

In conducting post-mortems, personal safety is paramount—both from the risk of exposure to animal pathogens and the physical risks involved with using sharp equipment. Post-mortems are sometimes carried out in less than ideal situations and under time pressures. However, it is essential for veterinarians to ensure their personal safety and follow standard procedures to reduce the risk of accidents.

There are many detailed guides on post-mortem procedures. In general, it is important for veterinarians to:

  • have a standardised procedure that you follow routinely. It is important not to deviate based on initial findings or a narrow differential diagnosis list
  • work safely for the benefit of themselves and others nearby
  • examine all organs and tissue systems in a systematic way, even if lesions appear to be confined to one system
  • record gross lesions in a report to give the reader a clear understanding of the lesions seen. Consider using a waterproof camera to record lesions that can be disinfected following the post-mortem
  • collect a comprehensive range of diagnostic specimens for consideration in the differential diagnosis
  • maintain and use sharp equipment
  • have all equipment available in an organised way
  • have a pre-arranged sample collection system (i.e. mark containers clearly (and ideally pre-label them)
  • place samples into appropriate collection containers
  • have and use a routine to maintain cleanliness
  • conduct more than one post-mortem
  • where possible, post-mortem freshly dead animals and consider sacrificing sick animals (since only limited information can be obtained from decomposed carcasses)
  • dispose of carcasses appropriately.

Samples for laboratory diagnosis

In the routine investigation of endemic diseases field diagnosis based on clinical, pathological and epidemiological evidence are adequate on many occasions. However, when faced with an outbreak of an unusual disease, possibly an EAD, it is crucial that an accurate confirmatory laboratory diagnosis is obtained as rapidly as possible. Failure to do so may compromise the success of any attempted eradication campaign.

Collecting and submitting a variety of samples allows for open-ended testing and increases the likelihood of accurate diagnosis. Multiple fixed tissues and sera allow for non-specific testing, and veterinary laboratories can hold extra samples pending the initial testing results.

You should contact the veterinary laboratories you use for their specific requirements and guidelines. Some diseases (e.g. bovine spongiform encephalopathy and scrapie) require specific samples. Details of special requirements are provided in the appropriate disease chapter in this guide. Later chapters will describe specific samples to submit by syndrome; however, a general description of samples to collect is shown in Table 1.3.3.

Table 1.3.3 Sampling guide for a base sample set
Sample typeExamples of samples to takeStorage/transport conditions
Ante-mortem samples

Blood samples (samples from at least 10 animals are recommended):

  • EDTA 10 ml
  • Plain 10 ml

Swab (ensure the swab fully absorbs sample fluid) e.g. oral, nasal, rectal

Blood samples:

  • mix with anticoagulant and chill
  • do not freeze
  • draw off serum for prolonged transport (put serum in plain blood tube)

Sterile swab in PBGS

Fresh tissue
(in separate individual sterile containers)

Tissue samples (samples from at least five animals are recommended) from organs relevant to clinical signs/gross necropsy findings, as well as:

  • brain (swab, small section)
  • liver
  • lung
  • kidney
  • spleen

Fresh samples:

  • chill or refrigerate
  • do not freeze
Fixed samples
(pooled in formalin – 10:1 formalin: tissue)
Tissues from lesions and representative samples from each organ system

Fixed tissues:

  • keep at room temperature
  • can be pooled
Labelling of samples

Note that:

  • each specimen container should be clearly labelled with the property and animal identification, date of collection and the tissue enclosed
  • waterproof labels/labelling used should stay attached and writing remain legible if the outside of the containers become wet.
Documentation to accompany samples

When you are outside of the infected area complete the relevant state laboratory submission form/specimen advice note. This specimen advice note is included inside the outer packaging (see section on sample packaging).

The specimen advice note should include:

Location and contact information

  • owner’s name and address of property, with appropriate contact information
  • name, address and contact information of the sender.

Case information

  • disease agents suspected and tests requested
  • species, breed, sex, age and identity of the animals sampled
  • date when samples were collected and submitted
  • list and type of samples submitted with transport media used
  • case history, including
    • list of animals examined and findings
    • clinical signs and their duration
    • length of time the sick animals have been on the premise and, if recent arrivals, where they originated from
    • date of first case and subsequent cases.

Epidemiological information

  • a description of the spread of infection in the herd or flock, for example, the number of sick or dead animals/number of exposed animals
  • different species on the property and numbers of each
  • type and standard of animal husbandry on the property, including the type of feed available, biosecurity measures and other relevant factors potentially associated with the occurrence of cases
  • history of foreign travel by owner or of introduction of animals from other countries or regions
  • any medication given to the animals, and when given
  • vaccination history describing the type of vaccines used and dates of application
  • other observations about the disease, husbandry practices and other disease conditions present.
Sample packaging

Package and transport all biological materials in accordance with local, national and international regulations. The minimum requirements for transporting specimens follow the principle of triple packaging, which consists of three layers—a primary receptacle (such as a blood tube or specimen container), secondary packaging (for example a plastic container), and an outer packaging.

In addition:

  • a primary container is packed into the secondary container on the infected property, along with absorbent material
  • the secondary container must have its surface disinfected and be removed from the infected area prior to packaging in the outer transport container
  • label the outer packaging with the name, address and 24-hour telephone number of the sender, the delivery address, orientation labels and any other relevant regulatory requirements
  • contact government veterinary laboratories regarding supplies of suitable packing containers
  • store suitable gel packs (‘cold bricks’) frozen at –20°C, ready for use
  • use dry ice if the journey is expected to take several days. Seal the sample containers to ensure that CO2 does not reach the samples, which could affect sample pH
  • seek advice from the appropriate government veterinary authority when carcasses or other specimens to be submitted are too large to be packed into a specimen transport container.
Transport of laboratory samples

Australia has strict regulations governing the road, rail and air shipment of clinical material and specimens. Specimens that are incorrectly packaged and labelled can be refused for transport or laboratory processing, and may put the safety of those receiving the specimens at unnecessary risk. For example leaking containers, blood in syringes, with or without needles, are unacceptable.

Veterinarians and clinic staff must ensure that packages containing biological material meet the requirements outlined in the current Australian Code for the Transport of Dangerous Goods by Road or Rail. It is recommended that commercial packaging and printed labels be used.

Consignments of specimens suspected of containing pathogens are considered to be dangerous goods (infectious substances). A person holding a current certification for dangerous goods must pack dangerous goods consignments for air transport. Mark the appropriate shipping name and number for the dangerous goods on the package. In most cases this will be UN 2900 (infectious substances, affecting animals only, in solid or liquid form) or UN 2814 (infectious substances, affecting humans, in solid or liquid form) or air or by post transport.

In either case, the actual name of the infectious agent (known or suspected) should be added in parentheses. Complete two copies of the shipper’s Declaration/or Dangerous Goods form for transport by air or by post. These must accompany the package, in the plastic envelope for shipping documents, attached on the side of the box.

The Animal Health Committee has developed protocols for the submission of likely EAD specimens to the Australian Centre for Disease Preparedness (ACDP). These are contained in the AUSVETPLAN management manual Laboratory Preparedness (pdf 284kb).

Follow-up

An important disease investigation principle is to follow-up with owners to determine if there are any ongoing concerns. Follow-up allows veterinarians to see if the situation has escalated or otherwise changed. You should not only rely on owners keeping you up to date with the clinical progression of the incident. Rather, actively make contact to monitor the situation, as this is a proactive way to ensure that an escalating situation does not go unnoticed. It can be beneficial to routinely schedule follow-up calls to producers after you have made livestock disease visits.

2. Guide to investigation of disease syndromes

2.1 Vesicular diseases

The term ‘vesicular diseases’ refers to a group of highly infectious viral diseases of cloven-hooved animals.

Due to the animal production and international trade ramifications of vesicular diseases, particularly foot-and-mouth disease (FMD), early detection of vesicular diseases is crucial. Vesicular diseases can cause high morbidity, but typically present with very low to no mortality.

Clinical signs

Clinical signs of vesicular diseases are similar. They include:

  • excessive salivation
  • lameness
  • reluctance to move, huddling together
  • vesicles and ulcers on the feet, mouth, and teats
  • hoof lesions including separation of corium
  • pyrexia and depression
  • unwillingness to eat.

In addition, secondary bacterial infections may lead to other clinical signs such as mastitis and reduced milk production in dairy cows.

Potential causes

A range of endemic and exotic infectious diseases present with vesicles and ulcerations, as well as several non-infectious diseases. Because of this, in addition to vesicles, you will need to consider other clinical signs present when determining a differential diagnosis list.

FMD is the most economically important vesicular disease for Australia and it affects multiple species (goats, sheep, cows and pigs). Because FMD is extremely contagious and an outbreak would have a significant economic impact to Australia, we must properly investigate and diagnose all vesicular diseases. Table 2.1.1 presents a list of vesicular diseases and the livestock species affected.

Table 2.1.1 The vesicular diseases (all are exotic to Australia) and species clinically affected
DiseaseCattleGoats and sheepDeerPigsHorses
Foot-and-mouth diseaseYesYesYesYesNo
Senecavirus A (Seneca Valley virus) infection(antibodies only; no disease to date)NoNoYesNo
Swine vesicular diseaseNoNoNoYesNo
Vesicular exanthema of swine (not seen globally since 1956)NoNoNoYesNo
Vesicular stomatitisYesNoNoYesYes

A number of other exotic diseases have similar clinical signs to viral vesicular diseases, particularly during their more advanced clinical stages. These include:

  • bluetongue disease (affects cattle, deer, goats and sheep)
  • peste des petits ruminants (affects goats and sheep)
  • rinderpest (now recognised as globally eradicated by the World Organisation for Animal Health (OIE) (affects cattle, goats and sheep).

Endemic diseases, which may cause similar clinical signs to viral vesicular diseases include, but are not limited to:

  • bovine papular stomatitis (affects cattle)
  • foot rot (affects cattle and sheep)
  • Glässers disease (Haemophilus parasuis) (affects pigs)
  • infectious bovine rhinotracheitis (affects cattle)
  • malignant catarrhal fever (only sheep-associated malignant catarrhal fever is endemic) (affects cattle)
  • mucosal disease caused by bovine viral diarrhoea (BVD). Only BVD virus 1 is endemic in Australia (affects cattle).

Non-infectious causes of similar clinical signs to viral vesicular diseases include but are not limited to:

  • chemical irritants and scalding (affects cattle, deer, goats, horses, pigs and sheep)
  • dermatophilus and other types of mycotic stomatitis (affects cattle, deer, goats, horses, pigs and sheep)
  • idiopathic vesicular disease in pigs (affects pigs)
  • insect bite hypersensitivity (affects cattle, deer, goats, horses, pigs and sheep)
  • lesions of the mouth and feet due to trauma (affects cattle, deer, goats, horses, pigs and sheep)
  • lameness due to bad or hard floors (affects cattle, deer, goats, pigs and sheep)
  • phototoxic dermatitis with vesicle formations from contact with the leaves of plants of the family Umbelliferae (parsley, parsnips and celery) (affects cattle, deer, goats, horses, pigs and sheep).

Some differential diagnoses may be eliminated by taking a thorough history including environmental observations (such as possible trauma or exposure to parsnips or celery) and a thorough clinical examination (such as for chemical burn). Also important is information about the clinical picture of the herd (i.e. are single or multiple animals affected?).

Reporting requirements

If you suspect a case of vesicular disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Investigation and sampling guidelines

Undertake a thorough physical examination of sick animals, including taking rectal temperatures. Speaking to the farmer and people who have cared for the animals will help establish the history for these cases. Conduct a post-mortem on any dead animals (but note that the vesicular diseases do not typically cause death). Animals may present with lameness and inappetence.

Investigate and sample of a range of animals, including at least 10 clinically healthy animals, to help identify new cases and determine the level of morbidity in the herd or flock.

Some differential diagnoses may be zoonotic and have public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

Take samples from at least five affected animals in the herd, flock or group. These can be taken from lesions in the mouth or the feet, or at other sites with suitable lesions.

The best samples for all vesicular disease exclusions are:

  • vesicular fluid
  • epithelium from unruptured vesicles (1–2 cm)
  • epithelial tags from freshly ruptured vesicles (1–2 cm)
  • nasal, oral and tonsillar swabs
  • oropharyngeal fluid, collected with a probang or swabs if unavailable
  • serum from affected, recovered and a selection of unaffected animals (minimum 7–10 ml; at least 10 animals per group).

Epithelium and granulation tissue from healing lesions that is difficult to detach and fibrin covered lesions are generally unsuitable for isolation of virus. If only older lesions are present, include samples from foot lesions as these tend to have higher concentrations of virus for longer periods than do lesions at other sites. To avoid bacterial contamination, you may need to wash animals’ feet and you may rinse epithelial samples from the foot in phosphate buffer before placing in sample vials.

In addition to samples from oral, foot and teat lesions, you should also collect fresh and formalin-fixed samples from several tissues (lymph nodes, thyroid and adrenal glands, kidney, spleen and heart) from dead animals.

Sample collection

The laboratory will be able to test for the presence of all vesicular viruses in samples. Refer to Table 2.1.2.

It is important to note that FMD virus is very sensitive to both acid and alkaline conditions and inappropriate buffer conditions can inactivate the virus making virus isolation difficult or impossible. To maximise chances of virus isolation:

  • use phosphate buffered saline or virus transport media with a pH of 7.6.
  • if a sample is to be submitted after 24 hours or more, glycerol should be added to the phosphate buffered saline
  • oropharyngeal fluid collected with a probang should be diluted in an equal volume of phosphate buffered saline pH 7.6, and mixed vigorously for 1 minute.

Note that collection of samples in these buffers is optimal (for the growth of FMD virus) but not essential for RNA or antigen detection assays.

Collect:

  • serum, 7–10 ml/animal in plain tubes
  • vesicular fluid, carefully use a syringe and needle to aspirate the vesicular fluid from unruptured vesicles, and place in a sterile container. Alternatively, collect fluid from small vesicles onto a swab and place the swab in 500 μl of buffer, such as phosphate buffered saline or virus transport medium
  • fresh tissue, epithelium, epithelial tags, oral, nasal and tonsillar swabs and oropharyngeal fluid and submit in phosphate buffered saline or virus transport medium, if available
  • fixed tissue, a range of tissues (lymph nodes, thyroid and adrenal glands, kidney, spleen and heart) from dead animals.
Table 2.1.2 Sample collection for vesicular diseases
Collection containerSample
Sterile tube (with viral transport media or phosphate buffered saline if available)Vesicle fluid, vesicle epithelium, nasal and oral swabs, oropharyngeal fluid collected with a probang or tonsillar swab
Plain tubeBlood for serology
Fresh and formalin-fixed samplesSeveral tissues (lymph nodes, thyroid and adrenal glands, kidney, spleen and heart) collected from dead animals
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin-fixed samples can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

2.2 Sudden death in pigs

Sudden death in pigs may be associated with a wide range of infectious diseases or non-infectious causes. Some of these infectious diseases are exotic to Australia and need to be excluded from the disease investigation.

Clinical signs

Sudden death can be defined as death occurring with little or no observed clinical signs. In most cases pigs will be found dead, often in good body condition. As such, there is increased importance placed on post-mortem evaluation and diagnostic testing as part of the disease investigation process. In addition, close observation of remaining animals may be useful in attempting to detect peracute clinical signs. Clinical signs (if observed) will depend on the aetiological agent involved and the age of the animals affected.

The epidemiological picture may also help to determine whether an exotic disease is involved with a sudden death incident. In most cases, an exotic disease will affect multiple animals and spread rapidly throughout the herd.

Potential causes

Exotic diseases that may cause sudden death in pigs include:

Note that while classical swine fever and Aujeszky’s disease are not typically associated with sudden death, the acute form of these diseases may cause sudden death in young piglets. Some strains of FMD virus can also cause peracute disease leading to sudden death in very young piglets.

Endemic diseases that may cause sudden death in pigs include:

  • Actinobacillus suis in piglets
  • bacterial endocarditis in piglets, weaners, growers and finishers
  • Bungowannah virus in piglets
  • colibacillosis (Escherichia coli) in piglets and weaners
  • erysipelas (Erysipelothrix rhusiopathiae) in growers and finishers
  • encephalomyocarditis (Encephalomyocarditis virus) in piglets
  • Glässers disease (Haemophilus parasuis) in weaners, growers and finishers
  • oedema disease (E. coli) in weaners, growers and finishers
  • pleuropneumonia (Actinobacillus pleuropneumoniae) in weaners, growers and finishers
  • streptococcal septicaemia in weaners, growers and finishers.

Non-infectious causes of sudden death in pigs include:

  • electrocution
  • endotoxic shock (e.g. from vaccines)
  • gastric ulceration
  • intestinal torsion
  • mulberry heart disease (in weaners)
  • overlay (in piglets)
  • porcine stress syndrome (in growers and finishers)
  • trauma.

Reporting requirements

If you suspect an emergency animal disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Investigation and sampling guidelines

Examine live pigs to detect early clinical signs. In cases of sudden death, undertake a thorough post-mortem examination of multiple pigs to narrow the diagnostic pathway and collect appropriate samples for diagnostic testing. Information about the housing environment, stocking rates, production flow and other rearing details can also help narrow the investigation.

Investigate and sample a range of animals, including at least 10 clinically healthy animals, to help identify new cases and determine the level of morbidity in the herd.

Some differential diagnoses may be zoonotic and have serious public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

Take samples from multiple dead pigs (at least five if possible) at post-mortem. Collect blood from at least 10 animals (if possible) that have clinical signs. Euthanise some animals for post-mortem examination and sample collection.

Sample collection

Table 2.2.1 details the sample collection required for sudden death in pigs.

Table 2.2.1 Sample collection for sudden death in pigs
Collection containerCollect from live pigsCollect from dead pigs
EDTA tubeBloodBlood (if possible to collect from recently dead animals)
Plain tubeBlood for serology
Swabs in virus transport mediumVesicular lesions (if present); nasal, oral cavity, tonsilsVesicular lesions (if present); nasal and oral cavity
Sterile tubeVesicular fluid (if vesicles present); faeces (if enteric disease suspected)Vesicular fluid (if vesicles present); faeces (if enteric disease suspected)
Sterile collection container (no media)Tonsil, spleen, lymph nodes, lung, brain, kidney, ileum
10% neutral buffered formalinTonsil, spleen, lymph nodes, lung, brain, kidney, ileum
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

2.3 Respiratory diseases in pigs

Respiratory pathogens are an important cause of morbidity, mortality and production losses in intensively reared pig herds. Multiple infectious diseases often occur concurrently or as a complex within a herd (known as the Porcine Respiratory Disease Complex), and diagnostic approaches should take this into consideration. Complex bacterial pneumonia is often the cause of death in cases of a porcine respiratory disease.

However, diseases such as pneumonia often result from the confluence of multiple host, environmental, management and pathogen factors.

Clinical signs

In many cases, the clinical manifestations of infection and severity of disease is age-dependent (e.g. porcine reproductive and respiratory syndrome). General clinical signs associated with respiratory pathogens may include:

  • anorexia/weight loss
  • coughing and nasal discharge
  • cyanosis, particularly the skin on the nose and ears
  • pyrexia
  • lethargy
  • sudden death
  • tachypnoea, dyspnoea, respiratory distress (increased respiratory effort/heaves, open mouth breathing).

Other body systems may be implicated:

  • encephalitis (associated with Aujeszky’s disease and Nipah virus infection)
  • lymphadenopathy (associated with porcine circovirus type 2 viruses)
  • polyserositis (associated with Haemophilus parasuis)
  • reproductive loss (associated with porcine reproductive and respiratory syndrome)
  • seizures and neurological signs associated with meningitis (e.g. Strepococcus suis).

Potential causes

The presence of multiple concurrent pathogens often complicates investigation of porcine respiratory disease. Although clinical and pathology findings may be most consistent with a bacterial aetiology, you should also consider viral and mycoplasmal pathogens. Carefully consider both infectious and non-infectious causes.

Exotic diseases that may cause porcine respiratory disease include:

Endemic diseases that may cause porcine respiratory disease include:

  • Actinobacillus pleuropneumoniae
  • atrophic rhinitis (Bordatella bronchiseptica)
  • inclusion body rhinitis (porcine cytomegalovirus)
  • miscellaneous opportunistic bacterial infections (Haemophilus parasuis, Pasteurella
  • multocida, Streptococcus suis)
  • mycoplasmal pneumonia (Mycoplasma hyopneumoniae, Mycoplasma hyorhinis)
  • porcine circovirus type 2 associated diseases
  • influenza A viruses (human-origin strains, subtypes H1N1, H1N2 and H3N2).

A non-infectious contributing factor to the development of porcine respiratory disease complex is poor air quality, such as high levels of dust and ammonia. In addition, pneumonia associated with ingested toxins (e.g. pyrrolizidine alkaloids, paraquat) is an uncommon cause of respiratory disease in pigs.

Reporting requirements

If you suspect an emergency animal disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Investigation and sampling guidelines

Undertake a thorough physical examination of sick animals, including taking rectal temperatures. Speaking to the farmer and people who have cared for the animals will help establish the history for these cases. Information concerning housing, environment, stocking rates, production flow and other rearing details can also help narrow the investigation. Conduct a post-mortem on any dead animals.

Some differential diagnoses may be zoonotic and have serious public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

Collect samples from multiple animals, particularly when multiple pathogens are suspected. Aim to collect blood from at least 10 animals and other samples from at least five animals.

Sample collection

Table 2.3.1 details the sample collection required for respiratory diseases in pigs.

Table 2.3.1 Sample collection for respiratory diseases in pigs
Collection containerCollect from live pigsCollect from dead pigs
EDTA tubeBloodBlood (if possible to collect from recently dead animals)
Plain tubeBlood for serology
Swabs in virus transport mediaVesicular lesions (if present); nasal, oral cavity, tonsilsNasal and oral cavity, tonsils, trachea
Sterile swabs for bacterial cultureVesicular fluid (if vesicles present); faeces (if enteric disease suspected)Pleural cavity, lung, pericardial fluid, brain
Sterile collection container (no media)Tonsil, trachea, lymph nodes (bronchial), heart, lung, brain, kidney, ileum
10% neutral buffered formalinTonsil, trachea, spleen, lymph nodes (bronchial), heart, lung (representative sections of all lobes, any lesions), brain, kidney, ileum
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

2.4 Neurological diseases in pigs

A large number of conditions affect the porcine nervous system, and many of these can cause sudden onset or acute outbreaks. The presenting signs of many of these conditions do not allow clinical differentiation, and diagnostic gross changes are infrequently found in the brain and spinal cord. Several emergency animal diseases can cause neurological disease in pigs so careful workup of these conditions is necessary.

Clinical signs

It is difficult to undertake all but the simplest neurological examination of a pig, and few diseases of the nervous system have localising signs. Clinical signs of neurological disorders in pigs include:

  • ataxia
  • blindness
  • circling
  • convulsions
  • hyperaesthesia
  • nystagmus
  • paralysis/paresis
  • recumbency
  • tremor.

Potential causes

Consider other clinical signs present when determining a differential diagnosis as many emergency animal diseases of pigs cause neurological disease.

Exotic diseases that may cause neurological disorders in pigs include:

Endemic diseases that may cause neurological disorders in pigs include but are not limited to:

  • congenital tremors (exact cause yet to be determined)
  • encephalomyocarditis virus (EMC)
  • enteroviral encephalomyelitis
  • Glässer’s disease (Haemophilus parasuis)
  • haemagglutinating encephalomyelitis virus (HEV)
  • Menangle virus
  • oedema disease
  • streptococcal meningitis
  • tetanus.

Non-infectious causes of neurological disorders in pigs include:

  • congenital defects
  • hypoglycaemia
  • iron toxicity
  • middle ear infection
  • nutritional deficiencies (e.g. pantothenic acid)
  • poisons such as arsenic, mercury, monensin and organophosphorus compounds
  • porcine stress syndrome
  • water deprivation or salt poisoning.

Reporting requirements

If you suspect an emergency animal disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Investigation and sampling guidelines

Undertake a thorough physical examination of sick animals. Speak to the farmer and people who have cared for the animals to establish the case history. Information about housing, environment, stocking rates, production flow and other rearing factors could be particularly useful. Conduct a post-mortem on any dead animals.

Some differential diagnoses may be zoonotic and have serious public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

Take samples from several pigs. Aim to collect blood samples from at least 10 pigs and other samples from at least five pigs. Investigate and sample a range of animals, including clinically healthy or suspicious animals.

Take a complete set of tissue samples for histopathology from recently deceased or euthanased untreated animals.

Sample collection

Table 2.4.1 details the sample collection required for neurological pigs.

Table 2.4.1 Samples to collect from neurological pigs
Collection containerCollect from live pigsCollect from dead pigs
EDTA tubeBloodBlood (if possible to collect from recently dead animals)
Plain tubeBlood for serology
Sterile collection container (no media)Tonsil, spleen, lymph nodes, lung, brain, spinal cord, kidney, ileum
10% neutral buffered formalinTonsil, spleen, lymph nodes, lung, brain, spinal cord, kidney, ileum
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

2.5 Diarrhoea in pigs

Pigs of all ages are susceptible to enteric diseases, and diarrhoea is a clinical sign common to nearly all enteric disorders. Of all the diseases in the sucking piglet, diarrhoea is the most common and probably the most important. In some outbreaks it is responsible for high morbidity and mortality. In a well-run herd there should be less than 3 per cent of litters at any one time requiring treatment and piglet mortality from diarrhoea should be less than 0.5 per cent.

Clinical signs

Diarrhoea in pigs may occur with little or no other signs or it may be a striking clinical sign of a specific disease. In addition to diarrhoea, clinical signs can include:

  • pyrexia (rectal temperature recorded at >39.5°C)
  • lethargy
  • reduced food intake
  • reluctance to move, huddle together
  • sunken eyes
  • sudden death in young pigs
  • wetness and discoloration of skin around the anus and tail.

Potential causes

Diarrhoea in a herd may be due to a single agent but concurrent infections are common and less than ideal environmental conditions can exacerbate these.

Exotic diseases that may cause diarrhoea in pigs include:

Endemic diseases that may cause diarrhoea in pigs include but are not limited to:

  • clostridium
  • coccidiosis
  • colibacillosis
  • internal parasites
  • porcine circovirus 2 infection
  • proliferative enteropathy (ileitis)
  • rotavirus infection
  • salmonellosis
  • swine dysentery
  • yersiniosis.

Non-infectious causes of diarrhoea in pigs include:

  • copper poisoning
  • fluoride toxicity
  • fungal/toxic mould poisoning
  • iron toxicity in piglets
  • lead poisoning
  • mercury toxicity
  • organochlorine toxicity
  • organophosphate toxicity
  • overfeeding
  • pantothenic acid deficiency
  • paraquat poisoning
  • phosphorus toxicity
  • salt poisoning
  • zinc deficiency.

Reporting requirements

If you suspect an emergency animal disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Investigation and sampling guidelines

A thorough physical examination of sick animals, including taking rectal temperatures, is advised. Speaking to the farmer and people who have cared for the animals will help establish the history for these cases. Conduct post-mortems on dead animals.

Some differential diagnoses may be zoonotic and have serious public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

Take samples from several pigs. Aim to collect blood samples from at least 10 pigs and other samples from at least five pigs. Investigate and sample a range of animals, including clinically healthy or suspicious animals.

Take a complete set of tissue samples for histopathology from recently deceased or euthanased untreated animals.

Sample collection

Table 2.5.1 details the sample collection required for pigs with diarrhoea.

Table 2.5.1 Samples to collect for pigs with diarrhoea
Collection containerCollect from live pigsCollect from dead pigs
EDTA tubeBloodBlood (if possible to collect from recently dead animals)
Plain tubeBlood for serology
Sterile tubeFaecesFaeces
Sterile collection container (no media)Tonsil, spleen, lymph nodes, lung, brain, kidney, ileum
10% neutral buffered formalinTonsil, spleen, lymph nodes, lung, brain, kidney, ileum
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4°C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20°C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

2.6 Acute lameness in ruminants and pigs

Acute lameness is a condition with a wide variety of potential causes which can be accompanied by many other clinical signs. It is important to differentiate between lameness and neurological weakness, or ataxia, since the main differential diagnoses of each vary widely. Due to the significance of some of the infectious causes, in particular the vesicular diseases, it is essential for them to be ruled out early.

Clinical signs

Acute lameness conditions can manifest in numerous different ways. Clinical signs that may be evident include:

  • abnormal posture and/or conformation
  • abnormal limb position
  • abrasions, lacerations, puncture wounds
  • areas of swelling, heat, erythema, pain, haemorrhage, ecchymosis
  • drop in milk production
  • drop in conception rates
  • hoof lesions including, but not limited to, interdigital dermatitis, ulcers, abscesses, vesicles, cracks
  • isolation from the herd
  • increased time in sternal and/or lateral recumbency
  • odour of the hoof
  • reluctance to move
  • swollen joints
  • sudden onset of mild to severe abnormal gait (affecting one or more limbs)
  • weight loss and/or dehydration.

If acute lameness is secondary to a systemic condition, signs that may be evident include (but are not limited to):

  • diarrhoea
  • drooling
  • generalised lesions present elsewhere on the body
  • pyrexia
  • systemic bacterial infections including acidosis, mastitis and metritis.

Potential causes

Acute lameness is associated with a range of infectious (both endemic and exotic) and non-infectious conditions. The systems most often associated with acute lameness are the musculoskeletal and nervous systems. In addition to acute lameness, consider other clinical signs when determining a differential diagnosis list.

Exotic diseases that may cause lameness in pigs and/or ruminants are:

Endemic diseases that may cause lameness in pigs and/or ruminants include but are not limited to:

  • bacterial infections causing acute arthritis, such as Erysipelothrix rhusiopathiae, Haemophilus parasuis, Streptococcus spp, Actinobacillus suis, Mycoplasma hyosynoviae, Mycoplasma hyorhinis, Arcanobacterium pyogenes, Chlamydia psittaci, Streptococcus suis (affects pigs)
  • botulism (affects cattle, goats, pigs and sheep)
  • bovine cysticercosis (beef measles) (affects cattle)
  • bovine ephemeral fever(affects cattle)
  • bovine papular stomatitis(affects cattle)
  • Brucella suis (affects pigs)
  • caprine arthritis encephalitis (affects goats)
  • clostridial myositis/blackleg (Clostridium chauvoei) (affects cattle and sheep)
  • contagious pustular dermatitis (orf) (affects sheep)
  • digital dermatitis (affects cattle and sheep)
  • flavivirus infection (affects cattle, goats, pigs and sheep)
  • footrot (affects cattle and sheep)
  • Glässers disease (Haemophilus parasuis) (affects pigs)
  • malignant catarrhal fever (affects cattle)
  • osteomyelitis (affects cattle, goats, pigs and sheep)
  • tetanus (affects cattle, goats, pigs and sheep).

Non-infectious causes of lameness in pigs and/or ruminants include:

  • bad/hard floors (affects cattle, goats, pigs and sheep)
  • degenerative causes—degenerative joint disease, arthritis, osteochondrosis, cervical spondylopathy (affects cattle, goats, pigs and sheep)
  • inflammatory causes—laminitis, septic arthritis (affects cattle, goats, pigs and sheep)
  • nutritional causes—white muscle disease (selenium deficiency), acidosis (laminitis), vitamin and mineral excesses and deficiencies leading to metabolic bone disease which predisposes fractures (osteomalacia, osteoporosis). Deficiency in vitamin D, biotin, manganese or zinc, as well as mineral excesses, may all lead to metabolic bone disease (affects cattle, goats, pigs and sheep)
  • overgrown claws (affects cattle, goats, pigs and sheep)
  • traumatic causes—hoof lesions (such as cracks, erosions, ulcers, abscesses), fractures, luxations and subluxations, nerve damage due to trauma or toxicity, soft tissue injuries (affects cattle, goats, pigs and sheep).

Some of the differential diagnoses may be eliminated by taking a good history (e.g. possible trauma, nutrition) and by undertaking a thorough clinical examination. Information about the clinical picture in the herd (i.e. single or multiple animals affected) is also important.

Reporting requirements

If you suspect an emergency animal disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Bluetongue, malignant catarrhal fever, Brucella suis, virulent footrot and the vesicular diseases are all notifiable diseases in Australia.

If you suspect the presence of any of these diseases in any livestock you are required to report it to your relevant state department. Virulent footrot must be reported within 48 hours.

Investigation and sampling guidelines

Undertake a thorough physical examination of sick animals, including taking rectal temperatures, as many conditions present as acute lameness. Speaking to the farmer and people who have cared for the animals will help establish the history for these cases. Conduct a post-mortem on any dead animals (but note that lameness does not typically cause death).

Some differential diagnoses may be zoonotic and have public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

You will only need samples from animals with acute lameness if you suspect infectious, inflammatory or nutritional causes. Physical examination alone will generally diagnose traumatic causes (such as a fracture or sole abscess). Sample collection depends on the clinical signs present and your physical examination findings.
Take samples from several affected animals in the herd, flock or group. Aim for blood samples from at least 10 animals and other samples from at least five animals.

Sample collection

Carefully aspirate the vesicular fluid from unruptured vesicles by syringe and needle, and place in a sterile container. Alternatively, collect fluid from small vesicles on a swab and place the swab in 500 μl of buffer, such as phosphate buffered saline or virus transport medium.

Submit epithelium, epithelial tags, oral, nasal and tonsillar swabs, and oropharyngeal fluid in phosphate buffered saline or virus transport medium, if available. Table 2.6.1 details the samples to collect for acute lameness in pigs and ruminants.

Table 2.6.1 Samples to collect for acute lameness in pigs and ruminants
Additional clinical signsSampleCollection container
VesiclesVesicle fluid, vesicle epithelium, nasal and oral swabs, oropharyngeal fluid collected with a probang or tonsillar swab
blood for serology
Sterile tube (with viral transport medium or phosphate buffered saline if available)
plain tube
Pyrexia, acidosis, mastitis, metritis, generalised lesions, drooling, diarrhoeaBlood for serology
whole blood
Plain tube
EDTA tube
Lesions (non-vesicular)Tissue material/epitheliumSwab or scrape using scalpel
if infectious aetiology is included in the differential diagnosis, use viral transport media
Joint effusion, localised swelling, or effusionFluid aspirate from affected joint or area
paired serology
Sterile container
plain tube
Interdigital dermatitisEpithelium from affected skin or advancing underrun lesions2–3 mm, modified Stuart transport medium
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

2.7 Reproductive problems in pigs

Viral infections are the most common infectious cause of reproductive problems in pigs. Porcine reproductive and respiratory syndrome currently accounts for nearly 60 per cent of infectious abortions in the United States. Infection of the foetus is common, although maternal illness can be a primary or contributing cause of abortion with a number of viruses.

Clinical signs

Reproductive problems in pigs can present in many different ways, but can include:

  • abortions
  • congenital abnormalities
  • embryonic death
  • embryonic death and resorption
  • foetal malformations
  • foetal mummification
  • increased neonatal mortality
  • poor conception rates
  • small litters and decreased litter size
  • stillbirths
  • weak pigs.

Potential causes

Exotic diseases that may cause reproductive problems in pigs include:

Endemic diseases that may cause reproductive problems in pigs include:

  • bovine viral diarrhoea (BVD) or border disease
  • Brucella suis
  • chlamydiosis
  • encephalomyocarditis virus infection
  • influenza A viruses in pigs (human-origin strains, subtypes H1N1, H1N2 and H3N2)
  • Menangle virus infection
  • porcine parvovirus infection
  • porcine cytomegalovirus infection
  • porcine rubulavirus (blue-eye disease)
  • Teschen/Talfan disease.

Non-infectious causes of reproductive problems in pigs include:

  • carbon monoxide poisoning
  • poor management
  • poor nutrition
  • zearalenone poisoning.

Reporting requirements

If you suspect an emergency animal disease, report it immediately by phoning the Emergency Animal Disease Hotline on 1800 675 888, wherever you are in Australia. Alternatively, contact a government veterinarian in your state or territory.

Investigation and sampling guidelines

Conduct a thorough physical examination of sick animals (including taking rectal temperatures). Speak to the farmer and people who have cared for the animals to establish the history for these cases. Consider conducting post-mortems on any available dead animals.

Some differential diagnoses may be zoonotic and have serious public health implications. Take extra precautions investigating such diseases, including using appropriate personal protective equipment, to prevent infecting personnel by ingesting, inhaling infected aerosols, or contaminating mucous membranes or abraded skin.

Samples required

Since most infectious abortions are the result of foetal infections that occur more than 14 days after the sow became infected, sows may have antibodies at the time of the abortion. However, seroconversion in a sow aborting due to acute illness will not yet have occurred at the time of abortion.

Collect samples from several pigs (at least 10 animals for blood samples and at least five animals for other samples). Investigating and sampling a range of animals, including clinically healthy animals, can assist to identify new cases and determine the level of morbidity in the herd.

Sample collection

Table 2.7.1 details the sample collection required for pigs with reproductive problems.

Table 2.7.1 Samples to be collected from pigs with reproductive problems
Collection containerCollect from live pigsCollect from dead pigs
EDTA tubeBloodBlood (if possible to collect from recently dead animals)
Plain tubeBlood for serology
Swabs in virus transport mediaNasal and oral cavity, tonsilsNasal and oral cavity, tonsils, trachea
Sterile swabs for bacterial cultureAbdominal cavity, uterus peritoneal fluid
Sterile collection container (no media)Foetus, tonsil, spleen, lymph nodes, lung, brain, kidney, ileum
10% neutral buffered formalinTonsil, spleen, lymph nodes, lung, brain, kidney, ileum
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples at either 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

3. Emergency animal diseases

3.1 African horse sickness

Fast facts

African horse sickness (AHS) is an exotic arthropod-borne viral disease of Equidae transmitted by certain species of Culicoides.

Organism

AHS virus (AHSV):

  • has nine different serotypes
  • multiplies in regional lymph nodes and is followed by primary viraemia, with subsequent dissemination to target organs.
Susceptible species

AHS affects:

  • all species of Equidae (although not all show clinical signs)
  • dogs and camels (dead-end hosts).
Economic impact

There is potential for significant economic loss associated with high mortality in horses, as well as restrictions on animal movements and international trade.

Epidemiology

AHS:

  • distribution is determined by the presence of competent vectors
  • morbidity depends on species, previous immunity and the form of disease
  • can cause mortalities, with horses particularly susceptible (up to 95 per cent).
Transmission

Transmission occurs primarily through Culicoides vectors.

Clinical signs

The disease may present as a peracute (pulmonary) form, subacute oedematous (cardiac) form, and acute mixed form or as horse sickness fever. Clinical signs may include:

  • pyrexia
  • laboured breathing and coughing
  • pulmonary oedema
  • oedema of the head, conjunctiva, neck, brisket, ventral thorax and abdomen
  • death (which is common and can occur suddenly).
Post-mortem

Gross lesions vary depending on the form of the disease, and lesions are not pathognomonic. These may be found:

  • subpleural and interlobular oedema
  • subcutaneous and intermuscular connective tissue oedema.
Samples

Collect:

  • blood samples (EDTA and plain tubes)
  • lymph nodes (especially mesenteric and bronchial), lungs, spleen from dead horses.
Actions to take

If you suspect a case of AHS:

  • call the Emergency Animal Disease Hotline on 1800 675 888 immediately or contact a government veterinarian in your state or territory
  • isolate suspected cases and implement biocontainment protocols (including movement controls and protection of animals from vectors) until advised by government veterinary authorities.

Introduction

African horse sickness (AHS) is an arthropod-borne infectious (but non-contagious) viral disease affecting all species of Equidae.

Disease agent and susceptible species

African horse sickness virus (AHSV):

  • is a double-stranded RNA virus belonging to the genus Orbivirus and family Reoviridae
  • has nine different serotypes and some serotypes are cross protective
  • mainly affects equids, with horses, mules, donkeys and zebras the primary hosts
  • causes the most serious infections in horses (mortality up to 95 per cent)
  • is also known to affect dogs, usually (but not exclusively) following ingestion of virus-infected meat. However, dogs are considered dead-end hosts
  • is thought to be maintained in the environment in most regions of Africa by zebras which are often subclinically infected natural reservoir hosts
  • antibodies have been reported in camels and African elephants but these species are not considered significant in the epidemiology.
Distribution

AHS:

  • geographical distribution and seasonal occurrence are dependent on competent vectors,
  • and studying the dynamics and behaviour of Culicoides spp. is therefore essential to understanding the disease
  • appears to be seasonal in endemic areas, where it is preceded by seasons of heavy rain alternating with hot and dry climatic conditions
  • occurs in eastern and southern Africa (all serotypes of AHSV)
  • virus serotypes 2, 4 and 9 have been found in North and West Africa, from where they occasionally spread into countries surrounding the Mediterranean.

For the latest information on the distribution of AHS, refer to the WAHIS information database website of the World Organisation for Animal Health (OIE).

Occurrences in Australia

None reported.

Epidemiology

Modes of transmission

AHS is not contagious and does not spread by direct contact between horses.
Transmission occurs via:

  • vectors, during blood-feeding by Culicoides species—Culicoides imicola is the principal vector in Africa but is not present in Australia. However, other Australian Culicoides species could be involved. The virus has also been isolated from Rhipicephalus sanguineus (a dog tick) and Hyalomma dromedarii (a camel tick) and has been experimentally transmitted by mosquitoes, including Aedes aegypti and Culex pyriens, both of which are present in Australia.
  • wind, which was implicated in the dispersal of infected Culicoides in some epidemics
  • mechanical transmission by other biting flies, but these are unlikely to play a significant role
  • parenteral injection of infectious blood.
Disease dynamics

Following ingestion by a competent female Culicoides vector, the virus replicates in the insect gut then translocates and replicates in the salivary glands before infection of the next mammalian host. Following infection of a mammalian host:

  • multiplication of AHSV occurs in regional lymph node and is followed by primary viraemia, with subsequent dissemination to endothelial cells of target organs
  • the incubation period lasts 2–10 days, depending on viral load, viral virulence and host factors
  • the viraemic phase typically lasts only 2–8 days (for horses) but reservoir mammalian host species (such as zebra) have a longer infectious period
  • lifelong immunity following recovery is rare as different serotypes are not necessarily cross-protective
  • animals that survive infection do not become carriers of the virus
  • morbidity and mortality can be as low as 30 per cent and 10 per cent respectively in endemic areas
  • high morbidity and high case mortality (of up to 100 per cent) may occur in naïve horses.
Persistence of the agent

AHSV:

  • is inactivated in the laboratory with formalin, Virkon® S or radiation
  • is destroyed at a pH less than 6, or pH 12 or greater. Acidic disinfectants such as acetic or citric acid have been recommended for decontamination when warranted. Alkaline disinfectants such as sodium hypochlorite are also recommended
  • can survive in frozen meat, but is inactivated at temperatures greater than 60 °C
  • is rapidly destroyed in carcasses that have undergone rigor mortis due to pH fluctuations.

Diagnosis and pathology

Clinical signs

The disease may present as a peracute (pulmonary) form, subacute oedematous (cardiac) form, an acute mixed form, or as horse sickness fever.
Signs of the peracute pulmonary form (‘Dunkop’) include:

  • acute pyrexia, followed within a day or two by the sudden onset of severe respiratory distress
  • short incubation period, usually 3–4 days
  • tachypnoea, forced expiration, profuse sweating, spasmodic coughing and a frothy serofibrinous nasal exudate
  • forelegs spread apart stance, extended head and dilated nostrils dyspnoea, which usually progresses rapidly and causes death within a few hours after respiratory signs appear
  • pyrexia which subsides gradually while the breathing remains laboured for several days (in recovering animals).

Signs of the subacute oedematous cardiac form (‘Dikkop’) include:

  • a more protracted and milder incubation than the pulmonary form
  • pyrexia lasting less than a week
  • oedematous swellings appear in the supraorbital fossae and eyelids, spreading to involve the face, tongue, intermandibular space, laryngeal region, and sometimes the neck, shoulders and chest
  • absence of oedema of the ventral side and lower legs
  • severe depression, colic, petechiae or ecchymoses on the ventral surface of the tongue, and petechiae in the conjunctivae (all are usually seen in the terminal stages of the disease)
  • death from cardiac failure (which often occurs within 1 week of the onset of pyrexic reaction).

The acute mixed form is most commonly seen in outbreak cases, where the disease may cause mortality of up to 80 per cent. Signs include:

  • a mix of clinical signs from the pulmonary and cardiac forms of the disease
  • pyrexia
  • mild pulmonary or subclinical cardiac disease followed by oedema, cardiac failure or respiratory failure
  • death, usually occurring 3–6 days after the onset of pyrexic reaction.

A combination of pathologies (often not clinically apparent) are usually found at post-mortem.
Horse sickness fever is:

  • the mildest form of the disease
  • frequently not clinically diagnosed as mild pyrexia in animals may be subclinical
  • usually observed in donkeys, reservoir species (zebras) and partially immune horses infected with heterologous serotypes of the virus.
Pathology

Gross lesions are quite variable and depend on the form of the disease. In the respiratory forms of the disease, the followintg may be found:

  • interlobular oedema of the lungs
  • hydropericardium, pleural effusion
  • oedema of the thoracic lymph nodes
  • petechial haemorrhages of the pericardium.

In the cardiac forms of the disease, the following may be found:

  • subcutaneous and intramuscular gelatinous oedema
  • epicardial and endocardial ecchymosis, myocarditis
  • haemorrhagic gastritis.
Differential diagnosis

Consider in the differential diagnosis:

  • exotic diseases
    • dourine
    • equine encephalosis
    • equine piroplasmosis
    • equine viral arteritis (avirulent strains of the virus circulate in Australia)
    • Nipah virus infection
    • surra.
  • endemic diseases
  • non-infectious causes
    • acute poisoning (plant or chemical)
    • heat stress.

Samples required

Sample collection

Collect these samples from clinically affected animals:

  • serum, preferably paired sera
  • EDTA blood from live animals (at least 10 if possible), preferably at early pyrexic stages (7–10 ml per animal)
  • fresh tissue from lymph nodes (especially the mesenteric and bronchial nodes), lungs, spleen.
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples either at 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

Diagnostic tests

For AHS diagnosis:

  • serological tests available include complement fixation test (CFT), competitive blocking ELISA (which is serogroup specific based on VP7) and viral neutralisation
  • nucleic acid detection includes real-time reverse transcription polymerase chain reaction (real-time RT-PCR)
  • viral isolates can be detected in blood during the early pyrexic stage.

Reporting requirements

AHS is an OIE-listed disease and Australia has an international obligation to report cases. 

If you suspect AHS, report it immediately. Call the Emergency Animal Disease Hotline on 1800 675 888. You will be directed to your state or territory government.

Biocontainment and personal protective equipment

There are no public health implications for AHS, but you should implement biocontainment protocols until advised by government veterinary authorities. This includes isolating suspected cases (and protecting from vectors, if possible) and using and appropriately disposing of personal protective equipment such as gloves, coveralls and rubber boots (or disposable boots). You need to thoroughly disinfect and decontaminate clothing, vehicle and equipment before leaving the property.

Figure 3.1.1
Figure 3.1.1 Abundant froth draining from the nostrils reflects severe pulmonary oedema. Image: PIADC and CFSPH.
Figure 3.1.2
Figure 3.1.2 Severe interlobular oedema of the lungs with petechiae on the pulmonary pleura and the splenic capsule. Image: PIADC and CFSPH.

Further information

Carpenter S., Mellor PS., Fall AG., Garros C., Venter GJ. (2017) African Horse Sickness Virus: History, Transmission, and Current Status. Annu Rev Entomol. 62:343-58.

Center for Food Security & Public Health (2015). African Horse Sickness. Iowa: Iowa State University.

Robin M., Page P., Archer D., Baylis M. (2016) African horse sickness: The potential for an outbreak in disease-free regions and current disease control and elimination techniques. Equine Vet J. 48(5):659-69.

Scacchia M, Molini U, Marruchella G, Maseke A, Bortone G, Cosseddu GM, Monacoo F, Savini G, Pini A. (2015) African horse sickness outbreaks in Namibia from 2006 to 2013: clinical, pathological and molecular findings. Veterinaria Italiana. 51(2):123-30.

3.2 African swine fever

Fast facts

African swine fever (ASF) is an exotic highly contagious viral disease of swine clinically indistinguishable from classical swine fever.

Organism

ASF virus:

  • replicates in Ornithodoros ticks
  • is found in all tissues and body fluids
  • can survive >30 days in pig pens and >140 days in some pork products
  • strains vary greatly in virulence.
Susceptible species

Only pigs and other suid species are susceptible.

Economic impact

There is potential for significant economic loss associated with high mortality and morbidity in pigs, as well as restrictions on animal movements and international trade.

Epidemiology

ASF:

  • may cause morbidity approaching 100 per cent in naïve herds
  • mortality varies with strain virulence and ranges from 0–100 per cent
  • may be asymptomatic in wild pigs
  • incubation usually lasts 4–20 days.
Transmission

Transmission occurs via:

  • direct contact, usually oronasal
  • ingestion of contaminated swill
  • contact with infected carcasses
  • indirectly by breeding and fomites
  • insect vectors including Orthinodoros ticks (biological) and stable flies (mechanical).
Clinical signs

ASF clinical signs:

  • vary according to the disease form (peracute, acute, subacute or chronic) as influenced by the virus strain, route and dose of infection
  • include marked pyrexia, reduced food intake, erythema, cyanosis, recumbency, diarrhoea, abortion and death
  • in the chronic form, include transient recurring pyrexia, stunting, emaciation, multi-focal erythema, raised or necrotic areas, coughing and painless joint swelling.
Post-mortem

The most common lesions are:

  • haemorrhagic spleen (enlarged, friable, dark red or black)
  • haemorrhagic lymph nodes, kidney and heart
  • focal skin necrosis
  • fibrinous pericarditis
  • generalised lymphadenopathy
  • swollen joints
  • consolidated lobules in lung.
Samples

Also refer to the detailed section on sampling for sudden death in pigs.
Collect:

  • blood (EDTA and plain tubes) from living animals
  • fresh tissue from spleen, lymph nodes, kidney, lung and ileum on post-mortem.
Actions to take

If you suspect a case of ASF:

  • call the Emergency Animal Disease Hotline on 1800 675 888 immediately or contact a government veterinarian in your state or territory
  • isolate suspected cases and implement biocontainment protocols (including farm movement controls) until advised by government veterinary authorities.

Introduction

African swine fever (ASF) is a highly contagious disease of pigs. It is clinically indistinguishable from classical swine fever (CSF), and similar lesions seen at post-mortem examination. ASF and CSF can only be distinguished by laboratory testing.

Disease agent and susceptible species
  • ASF virus:
  • is an enveloped DNA virus, genus Asfivirus, family Asfarviridae
  • replicates in Ornithodoros ticks
  • is found in all tissues and body fluids
  • is highly resistant to inactivation
  • strains vary greatly in their virulence. Domestic and feral pigs (Sus scrofa) are the only susceptible mammalian species in Australia outside zoos. European wild boar are also susceptible to ASF and present similar clinical signs and disease dynamics to domestic pigs. In Africa, the warthog, giant forest hog, and bushpigs serve as wild suid reservoirs, and have an inapparent infection.
Distribution

ASF:

  • is present in most of sub-Saharan Africa
  • was first detected outside Africa in 1957 in Portugal, and then in Belgium, Brazil, Cuba, the Dominican Republic, France, Haiti, Italy, Malta, the Netherlands, Portugal and Spain from the 60s to 90s. The disease has since been eradicated from most of these countries, but is endemic in feral pigs in Sardinia, Italy
  • outbreaks have been reported since June 2007 in many countries—most notably in a number of countries in central Europe where the disease had not previously been reported, including Georgia and Russia
  • A major outbreak of ASF occurred in China in 2018 and subsequently spread throughout South-East Asia.

For the latest information on the distribution of ASF, refer to the WAHIS information database website of the World Organisation for Animal Health (OIE).

Occurrences in Australia

None reported.

Epidemiology

Modes of transmission

Transmission occurs via:

  • contact with infected carcasses—the carcasses of pigs that die during acute ASF contain more virus than carcasses of chronic carriers of ASF and are therefore more infective to other pigs. Carcasses of chronic carriers have also been linked to the spread of ASF
  • direct contact with infected pigs—the virus is shed in high concentrations in all secretions and excretions that contain blood. Oral and respiratory infection can also occur between pigs in close contact. Moving infected pigs is the most important way to spread disease between piggeries. Feral pigs could become an important reservoir of the virus in Australia
  • vectors—soft ticks belonging to the Ornithodorus spp. are important vectors of ASFV in parts of Africa. ASFV replicates in Ornithodoros ticks and infection can persist over long periods, allowing the virus to be transmitted during blood meals. Other haematophagous insects such as stable flies (Stomoxys calcitrans) feeding on viraemic pigs have been experimentally implicated in the mechanical spread of ASF. Two native species of Ornithodoros ticks are found in Australia—Ornithodoros capensis (penguin tick) and Ornithodoros gurneyi (inornate kangaroo tick). Although O. capensis only parasitises sea birds, O. gurneyi may feed on dogs, cattle, humans, horses, mice, rats, rabbits and kangaroos (its natural host)
  • contact with infected faeces and urine
  • semen and embryos—the virus is present in semen and artificial insemination can transmit the virus. The International Embryo Transfer Society has indicated that there is not enough information to reach a conclusion regarding the transmission risk of ASF virus via embryos, but you should assume transmission via embryo transfer until proven otherwise
  • ingesting contaminated swill—ASF virus has the ability to survive for many months in raw, unprocessed, frozen meat as well as meat stored at fridge temperatures and in some processed hams. Ingesting pig meat or products infected with the virus is an important means of spread, and is commonly the way it is introduced into a country. Australia has strict import conditions to address the risk of an ASF incursion and swill feeding is illegal
  • fomites—because of the stability of ASF virus in the environment, indirect contact by means of contaminated pig pens, vehicles and other fomites (such as hypodermic needles) is a very important means of spread of the disease
  • airborne spread—ASF virus is not transmitted in the air from one piggery to another, but it does spread via aerosols within a piggery. Respiratory infection can occur between pigs in close contact.
Disease dynamics
  • following infection via the upper respiratory tract, the virus replicates in the tonsils and lymph nodes draining the head and neck, followed by generalised infection via the blood stream
  • incubation period is usually between 4–20 days
  • clinical disease may be peracute, acute, subacute or chronic
  • in the acute form, has a duration of 1–19 days and case mortality rate of up to 100 per cent
  • in the subacute form, persists for longer (3–4 weeks) and the case mortality rate is lower, with deaths more likely in younger pigs
  • pigs that survive the acute disease or are infected by mild strains of the virus usually become chronically infected for at least several months. However, such pigs do not readily excrete the virus for more than about 5 or 6 weeks after their initial infection and their role in the spread of the disease after that is unclear.
  • it is reported that most recovered pigs are virus carriers for long periods, perhaps for life
  • transmission to other pigs through direct contact can occur for up to 1 month after recovery from infection.
Persistence of the agent

ASFV:

  • can survive at least 30 days in pens and up to 300 days in some pork products
  • is highly resistant to inactivation but can be killed by high temperatures and some disinfectants—potassium peroxymonosulfate, hypochlorites, and phenols and related compounds (cresols).

Diagnosis and pathology

Clinical signs

Signs vary according to whether disease is peracute, acute, subacute or chronic.

In the peracute form, pigs are usually found dead with no prior clinical signs and if seen before death have marked pyrexia and are moribund.

In the acute form signs are:

  • pyrexia up to 42°C
  • hyperaemia or cyanosis of extremities, particularly ears and snout
  • loss of appetite or irregular appetite
  • inability or unwillingness to stand up
  • convulsions
  • incoordination or stiff gait
  • huddling together or piling one on top of another
  • laboured breathing or coughing
  • dysentery or diarrhoea (often bloody)
  • conjunctivitis
  • mucopurulent nasal discharge
  • vomiting
  • abortion.

In the subacute form clinical signs are:

  • as for the acute form but generally milder and persisting longer (3–4 weeks)
  • pyrexia, which may fluctuate irregularly and may exceed 40.5°C
  • occasionally, a purple colour over the pig’s body
  • bleeding from injection sites
  • abortion.

In the chronic form (generally seen in pigs surviving the subacute form) signs are:

  • recurrent transient pyrexia
  • ill-thrift, stunting and emaciation
  • pneumonia
  • arthritis
  • cutaneous ulcers
  • poor body condition.
Pathology

In the peracute form pigs may show no gross lesions. In the acute form, findings include:

  • enlarged and haemorrhagic lymph nodes, often resembling blood clots
  • the gastrohepatic, renal, mesenteric and submandibular lymph nodes are most often affected
  • enlarged spleen (2–3 times its normal size), which may be necrotic, dark, friable or pulpy
  • haemorrhages in almost any organ which are most commonly seen on serosal membranes and in kidneys (as subcapsular petechiae), heart, urinary bladder, lung and gall bladder
  • septal oedema of lungs, resulting in prominent interlobular septa
  • fluid in body cavities.

In the subacute form findings are more variable than for the acute form and include:

  • lymph node and renal haemorrhage
  • enlarged but not congested spleen
  • lobular consolidation of cranial lung lobes
  • haemorrhage of the intestinal lining, lymph nodes and kidney.

In the chronic form findings include:

  • enlarged lymph nodes
  • fibrinous pericarditis and pleurisy
  • lobular consolidation of lungs, which may progress to lobular necrosis
  • small, hard, nodular white masses in lungs
  • arthritis
  • cutaneous ulcers
  • poor body condition
  • less commonly seen are haemorrhages in additional organs (petechiae, ecchymoses) and oedema in the lungs and gall bladder.
Differential diagnosis

Many other viral and bacterial pathogens of pigs that are often confused with ASF may cause concurrent infections. It is important to take into consideration that isolation of other pathogens does not exclude an underlying ASF virus infection. Consider in the differential diagnosis:

  • exotic diseases
  • endemic diseases
    • acute salmonellosis (diarrhoea)
    • acute septicaemia due to Streptococcus suis or Haemophilus parasuis (Glässer’s disease)
    • infection with other pestiviruses such as border disease virus and bovine viral diarrhoea virus (mucosal disease)
    • pasteurellosis (pneumonia)
    • porcine circovirus 2-associated diseases such as those seen in porcine dermatitis and nephropathy syndrome
    • erysipelas (haemorrhagic skin lesions).
  • non-infectious causes
    • heavy metal poisoning
    • salt poisoning with water deprivation
    • thrombocytopaenia purpura (haemorrhages, especially in pigs 2–3 weeks old)
    • warfarin poisoning (causing death with haemorrhages, generally sporadic)
    • any cause of chronic ill-thrift in pigs.

Samples required

Submit several pigs (at least five if possible) for post-mortem examination, as individual animals may present with great variability in lesions. Record a composite picture of all lesions seen.

Sample collection

Collect samples from affected, especially pyrexic, pigs killed immediately before a post-mortem examination and from pigs that have recently died (including stillborn piglets and aborted foetuses). Collect:

  • serum, 30 samples from suspected chronically infected animals
  • EDTA blood (7–10 ml/animal) from live, clinically affected animals
  • fresh tissue from the spleen, lymph nodes (gastro-hepatic, mesenteric and sub-mandibular) tonsils, lung, kidney and ileum (2 g of each tissue); bone marrow may also be useful from dead wild animals that have been dead for some time, as it is likely to be relatively well preserved
  • fixed tissue, a full range of tissues (including the brain) in neutral-buffered formalin.
Transport of samples

For transport:

  • chill blood samples and unpreserved tissue samples either at 4 °C, or with frozen gel packs
  • DO NOT FREEZE SAMPLES at -20 °C; it reduces the sensitivity when used for virus isolation and molecular diagnostic tests
  • send samples with dry ice if the journey is expected to take several days.
  • formalin fixed tissue can be sent at room temperature.
Sample submission

The relevant state or territory laboratory should coordinate sample packaging and consignment for delivery to the Australian Centre for Disease Preparedness.

Diagnostic tests
  • You must confirm the diagnosis by laboratory testing because there is considerable overlap in the clinical and pathological signs seen in ASF with those of a number of other diseases. For ASF diagnosis:
  • the initial approach is screening by real-time PCR (qPCR). An antigen ELISA is also available if required and virus isolation will be attempted. Further characterisation and genotyping by sequence analysis can be carried out on primary samples or on isolates
  • serological tests are available but are generally more important in defining the nature and extent of any outbreak, and in the proof-of-freedom phase
  • histopathology and immunohistochemical staining are also useful diagnostic tests.

Reporting requirements

ASF is an OIE-listed disease and Australia has an international obligation to report cases. 

If you suspect ASF, report it immediately. Call the Emergency Animal Disease Hotline on 1800 675 888. You will be directed to your state or territory government. 

Biocontainment and personal protective equipment

There are no public health implications for ASF, but you should implement biocontainment protocols until advised by government veterinary authorities. This includes isolating suspected cases and using and appropriately disposing of personal protective equipment such as gloves, coveralls and rubber boots (or disposable boots). You need to thoroughly disinfect and decontaminate clothing, vehicle and equipment before leaving the property.

Figure 3.2.1
Figure 3.2.1 Multiple sharply demarcated foci of cutaneous haemorrhage and/or necrosis; haemorrhagic lesions may contain dark red (necrotic) centres. Image: PIADC and CFSPH.
Figure 3.2.2
Figure 3.2.2 Haemorrhagic submandibular lymph nodes. Image: Australian Centre for Disease Preparedness.
Figure 3.2.3
Figure 3.2.3 Petechial haemorrhages in the intestines. Image: Australian Centre for Disease Preparedness.
Figure 3.2.4
Figure 3.2.4 Haemorrhagic fluid in the abdominal cavity. Image: Australian Centre for Disease Preparedness.

Further information

Penrith, M.L., Vosloo, W. (2009) Review of African swine fever: transmission, spread and control. J S Afr Vet Assoc. 80(2):58-62.

Penrith, M.L., Vosloo, W., Jori, F., Bastos, A.D. (2013) African swine fever virus eradication in Africa. Virus Res. 173(1):228-46.

Sánchez-Vizcaíno, J.M. (2010). Early detection and contingency plans for African swine fever. 24th Conference of the OIE Regional Commission for Europe, World Organisation for Animal Health, Astana, Kazakhstan.

John Allen
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Malcolm Anderson
Little Kingfisher Group
Hackney SA 5069

Hannah Bender
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Jemma Bergfeld
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

John Bingham
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Stuart Blacksell
Mahidol Oxford Tropical Medicine
Research Unit
Mahidol University
Bangkok Thailand 10400

Tim Bowden
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Andrew Breed
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Amy Burroughs
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Hendrik Camphor
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Patrick Cass
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Bronwyn Clayton
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Axel Colling
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Kerry Daly
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Debbie Eagles
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Iain East
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Daniel Edson
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Mark Ford
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Skye Fruean
Northern Australia Quarantine Strategy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Mahala Gunther
School of Animal and Veterinary Sciences
Charles Sturt University
Wagga Wagga NSW 2650

Kim Halpin
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Sam Hamilton
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Nick Harris
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Jacquelyn Horsington
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Clare Jones
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Ashley Jordan
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Anna Kabaila
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Louise Kench
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Janene Kingston
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Ross Lunt
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Heather McKimm
School of Animal and Veterinary Sciences
Charles Sturt University
Wagga Wagga NSW 2650

Corissa Miller
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Pat Mitchell
Australian Pork Limited
Barton ACT 2600

Andrew Moss
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Kelly Porter
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Louise Sharp
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Nagendra Singanallur
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Joanne Taylor
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Sally Thomson
Animal Health Policy
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

Wilna Vosloo
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Jianning Wang
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Natasha Webb
Animal Biosecurity
Department of Agriculture, Forestry and Fisheries
Canberra ACT 2601

John White
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Nicole Whitehouse
School of Animal and Veterinary Sciences
Charles Sturt University
Wagga Wagga NSW 2650

David Williams
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

Frank Wong
Australian Centre for Disease Preparedness
CSIRO
Geelong VIC 3220

This publication would not be possible without the generous support and assistance of many dedicated individuals. Organisational support was provided by Kelly Maher and editorial support was provided by Rhyll Vallis of the Department of Agriculture, Forestry and Fisheries. A full list of the other contributors is in the Contributors section. Funding for this publication was provided by the Australian Government’s Agricultural Competitiveness White Paper, the government’s plan for stronger farmers and a stronger economy.

Many of the images were sourced courtesy of the Center for Food Security and Public Health.

Download the template

Taking a history requires the collection of accurate, quality information. Preparing a standard history collection template can help with gathering evidence.

Biosecurity gear

  • Sets of clean overalls
  • +/- disposable overalls
  • Disposable gloves
  • Box of surgical masks
  • Safety glasses/goggles +/- disposable
  • P2 masks/ respirator
  • Sharps container
  • Detergent
  • Water
  • General purpose disinfectant
  • Boot cleaning container and brush
  • Equipment washing container and brushes
  • Alcohol-based hand wash
  • Plastic groundsheet (and tent pegs)
  • Large heavy-duty plastic bags and ties

Clinical equipment

  • Clinical thermometers
  • Stethoscope

Lab sampling gear

  • Plain blood tubes
  • EDTA tubes
  • Lithium heparin tubes
  • Sterile containers ‘yellow tops’
  • Large histopathology pots
  • Formalin 10%
  • Bacterial swabs
  • Viral swabs
  • Saline bottle
  • Slides and holders
  • Ziplock bags
  • Marker pens
  • Lab submission forms
  • Eskies and icepacks
  • pH test kit
  • Urine glucose test strips
  • Needles and syringes

Post-mortem equipment

  • Knives and sharpener
  • Rib cutters (pruning shears)
  • Scalpel handles and scalpel blades
  • Rat tooth forceps
  • Scissors
  • Axe and mallet (for brains)

Other

  • Digital camera/ phone in ziplock bag
  • Checklists, standard operating procedures (SOPs), guidelines folder
  • Hendra advice sheet
  • This field guide