WA Livestock Disease Outlook - for vets

Reporting livestock disease protects our ability to trade

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of livestock diseases that are reportable or affect trade. To gather this proof of freedom, the Department of Agriculture and Food, Western Australia (DAFWA) investigates cases where livestock show signs of disease similar to reportable or trade diseases.

The WA livestock disease outlook – for vets is collated from information collected by DAFWA and private veterinarians as part of proving Australia’s freedom from those diseases. In 2015/16, data from our surveillance systems allowed WA to access markets valued at $2 billion.

Recent significant cases submitted to the DAFWA Diagnostic Laboratory Services (DDLS)

Case data from March to May 2017

Rift Valley fever testing supports proof of disease freedom for export markets

• 15 Merino weaners died in a flock of 300 in the Great Southern.
• The animals showed progressive blindness and wasting leading to death.
• On postmortem, the rumen contents were yellow with a foul odour and the vet considered hypovitaminosis A, polioencephalomalacia or lupinosis as possible causes.
• Laboratory testing did not identify the cause of death, but low serum vitamin A levels in two sheep suggested that there could be a general deficiency among the flock. It was also recommended that paddocks be examined for Stypandra sp. or bracken ferns, which may cause blindness.
• Given the high mortality in young sheep, histopathology testing was undertaken to exclude Rift Valley fever (RVF) and to support Australia’s claim of freedom from this disease. Histopathological changes in cases of RVF may include haemorrhage on serosal surfaces and in abdominal organs, liver necrosis, effusions in the thorax and abdomen, jaundice and intestinal inflammation.

RVF is an arthropod-borne virus that affects primarily cattle, sheep and goats but humans and camels are also hosts. It has never occurred in Australia but could enter the country via infected people, livestock or vectors. Signs include high mortalities in young animals, pyrexia, abortions, and bloody diarrhoea. To report unusual disease signs or high mortalities, contact your local DAFWA vet or DDLS on (08) 9368 3351 or the emergency animal disease hotline on 1800 675 888. See the DAFWA website for a list of reportable diseases.

Neurological signs in a young steer

• A one-year-old Murray Grey steer presented with paresis and ataxia and was subsequently humanely euthanased.
• A postmortem performed found a blood clot in the ventral dura mater of the cervical spine, which suggested the neurological signs were due to cervical trauma. Other postmortem findings included acute rumenitis and chronic colitis and enteritis with coccidia present.
• Other conditions ruled out on the basis of sample testing included annual ryegrass toxicity (ARGT), lead toxicity, polioencephalomalacia and disorders of calcium and magnesium.
• Incidental findings were able to assist the producer in identifying herd health issues.
• Rumenitis can occur due to excessive grain and coccidia and other parasites may be exacerbated by wet weather conditions and high stocking densities.

Foot-and-mouth disease (FMD) excluded in a dairy cow in the South West

• A four-year-old dairy cow was found recumbent with an oral lesion. The cow had been ill-thrifty for three weeks since calving. There were reduced gut sounds, dry faeces and low body condition but no other significant findings.
• Given the presence of oral lesions, samples were taken to exclude FMD and vesicular stomatitis.
• There were no other signs of FMD such as sores around the feet and on the udder and there was no history indicating a likely introduction of FMD.
• Testing for FMD and vesicular stomatitis at DDLS and the Australian Animal Health Laboratory (AAHL) was negative.
• Subsequent samples taken from the cow at postmortem showed the likely cause of disease to be a post-calving bacterial metritis. Oral lesions were presumed to be due to trauma or burn.

Foot-and-mouth disease is an exotic, highly infectious viral disease that affects cloven-hoofed animals. Blisters may form in the mouth, nostrils, teats or interdigital areas. Vesicular stomatitis is another disease of cattle, pigs and horses that can cause blisters in the mouth and on teats and feet. Both diseases are notifiable due to the devastating consequences of outbreak in Australia. The producer who reported these signs to a vet helped to provide evidence that Australia remains free of FMD and vesicular stomatitis.

In late autumn/early winter, be on the lookout for:

Also include base samples and any clinical or gross lesions in submissions. For advice on sample submission, contact your DAFWA field veterinary officer, the sampling and postmortem resources webpage or phone the duty pathologist on +61 (0)8 9368 3351.