How surveillance underpins Australia's livestock market acccess
Australia’s access to markets for livestock and livestock products depends on evidence from our surveillance systems that we are free of reportable and trade-sensitive livestock diseases. To gather this proof of freedom, the Department of Agriculture and Food, Western Australia (DAFWA) investigates cases where livestock show signs similar to reportable or trade-sensitive diseases. The WA livestock disease outlook – for vets (WALDO) is collated from information collected by DAFWA and private veterinarians as part of proving Australia’s freedom from those diseases.
Recent significant cases submitted to the Animal Health Laboratories (AHL)
Mid-October to mid-November 2015
Transmissible spongiform encephalitis (TSE) exclusion in the South-West
- Neurological signs and weight loss were seen in a four-year-old Holstein-cross cow in a herd of 150.
- The mid-lactating cow rapidly developed acute ataxia, peripheral blindness, a right-sided head tilt and hypoaesthesia. There was no response to antibiotics, mineral supplementation and thiamine so the cow was euthanased and a post-mortem performed.
- Gross findings were a dry rumen content and inflamed abomasal mucosa. The neurological signs were likely to have reduced the cow’s ability to eat and drink.
- A basic sample set was collected at post-mortem, including whole brain for TSE exclusion testing as this animal presented with neurological signs, was older than 30 months and less than nine years of age.
- Australia must demonstrate to trading partners annually that it has tested animals in the correct age range showing signs similar to TSE with negative results. Testing for TSE is subsidised and supports WA’s continuing access to livestock markets. Read more on TSE testing and TSE brain removal tips.
- Histological examination of the brain sections proved negative for TSE but diagnostic changes for Listeria monocytogenes were seen in the brainstem and midbrain.
- Thiamine levels were in the normal range and annual ryegrass toxicity (ARGT) testing was negative.
- Listeriosis is a sporadic cause of encephalitis in ruminants and infection is secondary to damage to the oral mucosa, with subsequent tracking of the bacteria along cranial nerve pathways to the brain.
Newcastle disease (ND) exclusion in pigeons in the Perth area
- A pigeon owner lost 30 birds from a flock of 120 over a three-week period.
- All affected birds showed lethargy, diarrhoea and weight loss, which can be signs of Newcastle disease. Newcastle disease would have a devastating impact on the commercial poultry sector in WA, which is valued at about $300 million annually.
- The owner took sick birds to three different veterinary practices, who suspected bacterial and mycotic causes, but the birds did not respond to treatment. The third clinic submitted birds for post-mortem to AHL.
- Post-mortem revealed fibrinonecrotic serositis, air sacculitis and interstitial nephritis. One bird had intra-lesional bacteria.
- Microscopic findings consistent with pigeon paramyxovirus (PPMV) were observed in the kidneys and polymerase chain reaction (PCR) tests were performed at AHL and the Australian Animal Health Laboratory (AAHL). These tests ruled out Newcastle disease but confirmed PPMV Type 1.
- DAFWA put movement restrictions on the loft and provided the owner with biosecurity and PPMV vaccination advice.
- This is the first recorded case of PPMV in WA, which is a reportable disease.
- Further testing at AAHL has shown that this strain of PPMV poses no threat to chickens.
- Whenever significant mortality events occur, private veterinarians should recommend that the client undertake laboratory testing and include exotic disease in their differential diagnoses.
- DAFWA subsidises investigations into significant disease events to increase the likelihood of early detection of an emergency disease and to provide evidence of WA’s animal health status to trading partners.
- Read more on pigeon paramyxovirus and Newcastle disease.
Recent cases of jaundice, haematuria and lethargy in dairy cows
- In two cases on different properties, a seven-year-old Jersey cow that had calved 15 days ago and a six-year-old milking Friesian cow that had calved three weeks ago showed jaundice, haematuria and lethargy.
- The vet submitted blood and urine samples to AHL and PCR testing detected a Mycoplasma sp. in both cases. Phosphorus levels were normal and Theileria, Anaplasmosis and Leptospirosis tests were negative.
- Infection with a haemotropic Mycoplasma is thought to be common but clinical signs are infrequent. AHL requests that vets seeing similar cases report them so that contributing factors can be clarified.