Why DAFWA carries out surveillance for livestock disease
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 producers (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)
Case data from mid-March to mid-April 2015
Bluetongue virus ruled out in a case of sudden death in sheep
- A total of 52 ewes from a mob of 560 yellow tag ewes in the Wheatbelt died suddenly.
- The sheep had been grazing a blue lupin paddock over the past two months and had recently experienced an extreme storm weather event.
- A post-mortem on one animal showed jaundice with yellowing of body tissues including the liver.
- Laboratory testing revealed severe liver damage and damage to blood vessels in other tissues.
- Bluetongue virus, a reportable animal disease in WA, can cause similar changes in blood vessels so testing was undertaken at the Australian Animal Health Laboratory (AAHL) to rule out this disease. Testing proved negative as did testing for salmonella infection and annual ryegrass toxicity (ARGT).
- Lupinosis was accepted as the cause of the deaths.
Read more on bluetongue virus and lupinosis.
Transmissible spongiform encephalitis (TSE or mad cow disease) exclusion
- Weakness and collapse were seen in a six-year-old Friesian cow in the South West.
- Over a four-week period, the cow became lethargic and suffered a gradual drop in milk production. The cow did not improve following antibiotic, anti-inflammatory treatment and energy supplementation. After becoming weak and collapsing, the cow was euthanased humanely and a post-mortem performed.
- Laboratory testing of the brain for TSE proved negative.
- The producer received a $330 rebate from the National TSE Surveillance Program – read more at NTSESP.
- The blood samples showed liver damage, which was confirmed by tissue samples showing significant longstanding liver disease.
- The source of the liver damage was not determined in this case. Possible causes could include plant poisoning, bacterial infection or underlying metabolic disease.
Sudden death in Merino ewes
- Cases of sudden death were investigated in four-year-old Merino ewes in the Wheatbelt.
- In a mob of 800 ewes, 13 were found dead in one corner of the paddock. All animals were approximately two months pregnant and had a poor vaccination history.
- The mob was fed barley and lupins after a cold front/rain event, and deaths occurred the next day.
- A post-mortem was performed on one animal but there was no obvious cause of death. The rumen (first stomach) contained barley and lupins.
- Samples were taken and laboratory testing revealed kidney damage and irritation to the lining of the rumen. Damage to the kidneys and tissues of the rumen was found to be caused by a build-up of oxalate crystal deposits.
- The most common cause of oxalate poisoning is through access to oxalate-containing plants such as weed plants in stubble paddocks. The plant species to which these animals may have been exposed are being investigated.
- Oxalate poisoning commonly occurs following summer rain when sheep consume alternative feed sources when pasture feed is wet.
Suspected failure of passive transfer (FPT) of colostrum in seven-day-old calves
- Sudden death was investigated in one-week-old Angus calves in the Great Southern.
- In a mob with 40 newly born calves, seven were found dead.
- The dams were in good condition, had access to adequate pasture and were supplemented with oaten hay.
- All calves were of normal weight and had good body fat reserves showing good development.
- On post-mortem of one calf, its body tissues appeared very pale. Its intestinal system was filled with large amounts of black liquid (blood), with the lower intestines filled with dark tarry droppings. The blood had come from the lining of the rumen. No other abnormalities were found on post-mortem.
- Laboratory tissue tests revealed extensive damage and ulcerations to the lining of the rumen.
- Blood tests showed a moderately low total blood protein and other chemical evidence to indicate poor colostrum (first milk) transfer.
- Tests for evidence of salmonella bacterial infection, rotavirus and coronavirus infections were all negative.
- Failure of colostrum uptake leads to a greater risk of calves developing disease. In these cases it is thought that the normal diversion of milk in newborn calves to bypass the rumen and enter the lower stomachs did not function well, leading to milk fermenting in the rumen with subsequent ulceration and haemorrhage. Poor colostrum transfer can reduce a calf’s ability to cope with this condition.
In late autumn to early winter, be on the lookout for:
Annual ryegrass toxicity (ARGT)
- Farmers are advised to seek vendor declarations of ARGT status for bought-in hay, grain and chaff.
- Signs of ARGT include sudden death or agitation or excitement, unsteady walking and convulsions brought on by stress.
- Read more on ARGT.
Mastitis in ewes
- Mastitis is most common in ewes raising multiple lambs or with high milk production.
- Most cases occur during the first weeks after lambing or immediately before weaning.
- Good ewe nutrition and providing a clean lambing environment are important factors in reducing the incidence of mastitis.
- Read more on mastitis in sheep.
Secondary photosensitisation
- Secondary photosensitisation commonly occurs following liver damage from consuming plant toxins.
- Signs include severe irritation, restlessness, rubbing and shaking of head and ears, seeking shade, swelling of affected areas including ears, eyelids, lips and nose.
- Read more on photosensitisation in livestock.
Emergency Animal Disease hotline
Early recognition of disease is one of the most important factors influencing the control of disease and the reduction of its impact on industry and the community.
If you know or suspect that an animal is affected by a reportable disease, there is a legal obligation to notify the Department of Agriculture and Food, Western Australia (DAFWA) as soon as is reasonably possible. The DAFWA Animal Health Laboratories waives laboratory fees for investigations into cases of suspected reportable diseases.
During normal office hours, contact your nearest DAFWA field veterinary officer.
After hours, contact the emergency animal disease toll free hotline on 1800 675 888.
Diseases of significance to Western Australia that must be reported are listed on the following webpage: Reportable animal diseases - Western Australia.
Previous issues and to subscribe
To subscribe to WALDO - for producers or to view previous issues, visit the DAFWA newsletter archive page.
Feedback
To provide feedback, email Dr Bruce Twentyman on bruce.twentyman@agric.wa.gov.au