Recent livestock disease cases in WA

Weakness and deaths in sheep during lambing

• A total of 23 pregnant ewes presented with lethargy, recumbency and panting, with some progressing to death within 12 hours. The affected animals did not respond to treatment with electrolytes and glucose. Three of the ewes also had dystocias.
• The sheep had been on lupin and barley lick feeders for four weeks, and were trail fed prior to this. They had been vaccinated with a 6-in-1 vaccine (including clostridial diseases), drenched with a macrocyclic lactone within the last month, and recent worm egg counts [1] showed a low parasite burden in the flock.
• Post-mortem of two ewes found them to be in good body condition and at different stages of pregnancy. There was an acute vasculopathy affecting the brain of one ewe, while the other was too autolysed for reliable interpretation.
• Differential diagnoses: Anthrax [2] (reportable), 1080 or lead [3] poisoning and scrapie [4] where there are neurological signs.
• Key samples: in addition to the base sample set, fresh small intestinal contents (preferably ileal); fixed brain, 2cm of fresh spinal cord and dorsal cerebellum for TSE rule-out; peripheral blood and blood smears for anthrax rule-out. (Note: do not post-mortem an animal suspected to have died from anthrax; instead immediately contact the laboratory [5] to discuss safer sampling options [6] and to advise if samples are being sent.)
• Testing of the small intestinal contents returned a positive enterotoxaemia ELISA in the ewe with the vasculopathy. An exotic TSE was ruled out by histopathology.
• Follow-up investigation by the vet found that the younger ewes had been vaccinated against pulpy kidney in the previous year but the annual vaccination for older ewes had lapsed. The producer was also administering the initial vaccination course at two-week intervals instead of the recommended four weeks, which could explain losses in the younger animals.
• Read more on enterotoxaemia (pulpy kidney) in sheep [7].

[8]

Fig 1: Collect 50mL of ileal contents for bacterial culture and enterotoxaemia ELISA.

[9]

Fig 2: Normal sectioned kidney. Not all cases of pulpy kidney will have visible kidney lesions.

Sudden deaths and lethargy in cows at calving

• Thirteen cows died and 57 were lethargic and recumbent in a mob in the South West. A second mob in a neighbouring paddock seemed unaffected.
• The cows had been grazing a paddock without supplementary feed, had been drenched three months ago, and were up to date with vaccination.
• On post-mortem, one cow in poor body condition showed pallor of the mucous membranes, gelatinised perirenal fat, a thickened abomasum, enlarged mesenteric lymph nodes, and bright yellow fat.
• Differential diagnoses: toxicity (lupinosis [10], Paterson’s curse), helminthiasis, enterotoxaemia [7], annual ryegrass toxicity (ARGT) [11].
• Key samples: cow-side ketone test in milk or urine, blood in lithium heparin, gastrointestinal contents and sections (fixed and fresh), faeces, liver (fresh and fixed) in addition to base sample set.
• On histopathology, the cow had a chronic abomasitis and enteritis with nematodes present in the abomasum, a severe hepatic lipidosis, and splenic haemosiderosis. Blood BHB (beta-hydroxybutyrate) and liver enzymes were markedly elevated, contributing to a diagnosis of ketosis [12].
• The abomasal worm count was very high, including large numbers of L4 larvae, indicating a severe worm burden and pasture contamination which contributed to disease. It was recommended that these animals receive further drenching and monitoring by worm egg counts, as well as supplementary feeding. Information for drench management including resistance can be found on our webpage [13].

In early winter, watch for these livestock diseases:

 Note: Include base samples and any clinical or gross lesions in submissions. For sample submission advice, contact your DPIRD field vet [21] or the duty pathologist on +61 (0)8 9368 3351.

Useful resources

• Watch this short video [22] to learn more about DPIRD’s ewe abortion and newborn lamb deaths surveillance program and subsidised testing kits if your clients are experiencing losses during lambing season.
• Visit the sampling and post-mortem resources for vets webpage [23] for helpful resources such as a ruminant post-mortem bench aid [24].
• Last chance for vets to register for the upcoming disease investigation and emergency animal diseases workshops [25] at South Perth, 23-25 June. Click this link [25]for more details and how to register.
• DPIRD has posted a new webpage with resources and tools for producers for the 2018 season. [26]

Recent WA animal health media releases

• Producer fined for footrot quarantine breach [27]
• Targeted surveillance under way for Johne’s disease in cattle [28]
• Testing kits to lift lambing marking rates [29]
• Sheep producers reminded to watch for pregnancy toxaemia [30]
• Stock owners urged to check hay for annual ryegrass toxicity [31]

Veterinary investigations support our livestock industries and access to markets

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. Data from livestock disease investigations provide evidence that WA is free from these diseases and supports our access to markets.

Feedback and subscriptions

We welcome feedback. To provide comments on the veterinary edition of the monthly email newsletter or to subscribe, email waldo@dpird.wa.gov.au [32]. Producer versions of this newsletter are available on the WA Livestock Disease Outlook archive page [33].