Why DAFWA collects livestock disease surveillance information
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-July to mid-August 2015
Neurological signs in a Dorper sheep in the Wheatbelt
- A two-year-old White Dorper ewe was seen with neurological signs in the Wheatbelt.
- The animal had foreleg knuckling and an uncoordinated gait over two days yet mentation appeared normal.
- A post-mortem revealed a hypervascular and inflamed brain and increased fluid around the brain.
- A full set of tissue samples were taken for histopathology including fresh samples of brain tissue for transmissible spongiform encephalopathy (TSE) exclusion testing. TSE testing was negative. WA must test a target number of cases each year from eligible animals with neurological signs to provide proof that WA is free of TSE in order to support our export trade and public health obligations.
- The whole brain must be submitted for TSE exclusions to be carried out. See the following link for a printable PDF to guide brain removal and TSE submissions.
- Histopathology showed muscle tissue damage severe enough to explain the knuckling with no other changes in other tissues noted.
- Biochemistry showed low vitamin E levels and borderline selenium levels.
- In the absence of other findings and no history of access to toxic plants, nutritional myopathy was diagnosed.
- Read more on selenium and vitamin E deficiencies.
Sudden death in unweaned lambs in the Wheatbelt
- Sudden death in less than six-month-old unweaned lambs was seen in the Wheatbelt.
- Over a four-day period, 15 lambs died and 50 became ill in a mob of 900 Merinos.
- The lambs had been mulesed and marked six weeks ago and were on pasture with their dams.
- The lambs had been vaccinated with 6-in-1 at marking and the ewes had received a pre-lambing drench.
- Three lambs were examined and blood samples taken. All three had pale/white mucous membranes, no scours and a body condition score of two.
- Post-mortem examination on one lamb revealed a pale carcass, enlarged mesenteric lymph nodes, olive-coloured kidneys and light-brown liver.
- Testing of a full sample set revealed moderately severe, acute hepatocellular necrosis. Such a change may result from hypoxia/anoxia at the level of the hepatocyte, often seen when there is significant anaemia.
- Blood samples tested positive on ELISA for Mycoplasma ovis and eperythrozoonosis was diagnosed.
- Read more on eperythrozoonosis.
Anthrax exclusion in case of sudden death in calves in the western Midlands
- Cases of sudden death in 20 Hereford calves were investigated in the western Midlands.
- The animals were found dead with blood around the nose and eyes. Predation was excluded as a cause. Bleeding from orifices in cattle and sheep can be a presenting sign of anthrax.
- The animals had been exposed to plants in the genus Gastrolobium, which contain fluoroacetate. These were initially described as ‘bacon and egg’ plants, a non-specific term that describes plants in over 30 genera, and most of these plants are not toxic.
- A necropsy on one calf and histopathology showed acute myocardial necrosis consistent with fluoroacetate poisoning.
- Anthrax testing was negative. Anthrax is a zoonosis and can be fatal in humans. These cases were outside the known areas for Bacillus anthracis in WA but whenever veterinarians see animals with signs similar to anthrax, they should carry out a risk assessment and follow recommended sampling protocols for anthrax.
- Read more on anthrax.
Sudden death in ewe weaners in the Great Southern
- A mob of 700 ewe weaners were moved into a new paddock two to three weeks ago.
- The paddock contained capeweed, ryegrass and stubble from last season.
- 15 animals were found dead and one was seen staggering. The staggering animal was post-mortemed.
- There were signs of thickening of the small intestines, enlarged mesenteric lymph nodes and mild inflammation of the abomasum. Histopathology revealed subacute enteritis with associated bacterial colonies.
- Yersinia pseudotuberculosis was isolated in the faeces. Even though worm egg counts were low, helminthosis has been suggested as a predisposing cause of yersiniosis by causing villous atrophy.
- Yersiniosis is typically seen in young stock in wet and cold conditions.
- Yersinia organisms are zoonotic and can cause enterocolitis and polyarthritis in people.