WA Livestock Disease Outlook - for vets

Recent livestock disease cases in WA

Respiratory disease and deaths in calves in the far north

• In a mob of 150 calves, 7 were found dead and 15 affected with severe dyspnoea, laboured breathing and recumbency.
• The calves had been in yards for two weeks due to cyclonic weather. They were returned to pasture with clinical signs appearing a few days’ later.
• Of 4 calves necropsied, 3 had liver and lung abscesses.
• Laboratory testing showed pneumonia, hepatitis and pericarditis.
• The pneumonia was likely bacterial in origin with bacterial morphology consistent with Pasteurellacae. Fusobacterium was identified in the liver.
• The risk of bacterial pneumonia in calves may be increased during periods of close confinement and stress where the bacteria can be easily spread through aerosol and contact. The risk can be reduced by addressing stress factors where possible and ensuring good overall immunity.
• Key samples: Fresh lung and lung swab in gel transport medium. 
• Reportable rule-outs: The exotic disease, haemorrhagic septicaemia (caused by certain serotypes of Pasteurella multocida), and the reportable disease, anthrax, were ruled out by the laboratory testing, helping to support WA’s proof of freedom from these diseases. 

Lupinosis and nutritional myopathy cause deaths in Wheatbelt sheep

Yellow, swollen liver from sheep with acute lupinosis.

• More than 200 Merino wethers died on one property in January following summer rainfall.
• Sheep were grazing lupin stubble at the time and the initial 200 deaths were attributed to lupinosis.
• The sheep were immediately removed to oat stubble and were provided supplementary hay.
• Deaths in the flock began again a month later and further investigation was undertaken.
• Two sheep were submitted for postmortem: one with weakness, lethargy, recumbency and pallor; and one 4-year-old sheep with weakness and head pressing that later died.
• The first sheep had mild liver disease consistent with previous lupinosis. Changes in skeletal muscle and severely depressed plasma vitamin E indicated nutritional myopathy. Nutritional myopathy is usually associated with vitamin E or selenium deficiency but has also been associated with lupinosis.
• The second sheep had liver lesions consistent with chronic lupinosis due to previous exposure leading to hepatic encephalopathy.
• Key samples (include base sample set): Fresh and fixed liver and skeletal muscle, brain, blood, lupin samples.
• Reportable rule-outs: Given its age and the presence of neurological signs, the brain was submitted for testing for transmissible spongiform encephalopathies (TSE). The results ruled out TSE, which helps to support Australia’s proof of freedom from scrapie.
• A vitamin E drench for the flock would be advisable as would limiting unnecessary movement of the sheep to reduce the potential for further muscle damage and deaths from nutritional myopathy.