WA Livestock Disease Outlook - for vets

Livestock disease investigations protect our markets

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of particular livestock diseases. The WA livestock disease outlook – for vets summarises recent significant disease investigations by Department of Primary Industries and Regional Development (DPIRD) vets and private vets that contribute to that surveillance evidence.

Recent livestock disease cases

Neurological signs and collapse in a six-year-old sheep at abattoir

• A Merino sheep was recumbent at ante-mortem inspection with neurological signs including blindness, abnormal eye movements and tremors. The animal was in very poor body condition and tachycardic and was euthanased humanely.
• Histopathology showed a severe, chronic, granulomatous enteritis and lymphadenitis, serous atrophy of fat and a suppurative bronchopneumonia.
• These findings were consistent with a diagnosis of ovine Johne’s disease (reportable), which was further supported by a positive faecal PCR test.
• As the sheep was over the age of 18 months and showing neurological signs consistent with the exotic disease scrapie, the submitting vet supplied appropriate brain and spinal cord samples for transmissible spongiform encephalopathy (TSE) exclusion testing. The test results  were negative, adding support to Australia’s freedom from this disease.
• Rebates for private vets and producers are available for suitable investigations that support the National TSE Surveillance Program. Read more on how vets and producers can access these rebates.

Tremors and deaths in five-week-old pigs

• Two pigs had died and 50 were affected with recent onset of tremors from a group of 200 pigs. Some pigs had also lost body condition.
• The submitting vet had made a provisional diagnosis of salt toxicity. On histopathology, there was an acute polioencephalomalacia with marked eosinophilic infiltrates. These lesions occur secondary to sudden electrolyte shifts in the brain, and are characteristic of salt toxicosis in pigs.
• All livestock can be affected by salt toxicity if fresh water is unavailable for more than 24 hours.
• Signs include excessive thirst, diarrhoea, neurological signs, rapid loss of condition, often progressing to coma and death.
• Affected pigs may move round in a circle using one foot as a pivot and may convulse. Convulsions can re-occur at approximately seven-minute intervals. 
• When water supplies have been interrupted, stock should be slowly re-introduced to fresh water in small, frequent amounts until rehydrated. Also consider using oral electrolytes in the drinking water.
• Read more on preventing salt toxicity in livestock and salt poisoning or water deprivation in pigs.
• Given the sudden deaths, testing for the exotic diseases African swine fever and classical swine fever was conducted, with negative results.
• Vets are reminded to remain on high alert for any signs of African swine fever as its spread across the world continues, most recently to Papua New Guinea.

High mortality rate and respiratory signs in broiler chickens

• A poultry producer noted a higher than normal mortality rate in 20-day-old chickens with some birds showing dyspnoea and gasping.
• Given these clinical signs are suspicious for the reportable diseases avian influenza and Newcastle disease, testing for these diseases was conducted as a priority, and was negative.
• Further examination showed extensive granulomatous pneumonia with fungal hyphae consistent with aspergillosis. A microbial culture confirmed the presence of Aspergillus fumigatus in the lungs of five birds.
• Aspergillosis can occur when spores in contaminated feed, litter or soil are inhaled by poultry. Typical signs include dyspnoea (often seen as gasping) and acute mortality rates of up to 50%, most often in younger birds. A chronic form can also develop, more often seen in older birds.
• In the commercial layer and broiler industries, use of risk-based vaccination in layers and breeders reduces the risk of exotic or Australian-origin virulent Newcastle disease virus by improving flock protection against the virus and displacing precursor viruses.
• A resource guide is available on the DPIRD website for veterinarians investigating poultry diseases.

In autumn, be on the lookout for:

Pig post-mortem guide available from DPIRD

DPIRD has produced a step-by-step guide to a pig post-mortem to assist vets, a resource that will be particularly useful if African swine fever is suspected. See our post-mortem resources webpage to download a PDF copy, or email waldo@dpird.wa.gov.au to request laminated copies for your practice.