WA Livestock Disease Outlook - for vets

Livestock disease investigations protect our markets

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of particular livestock diseases. The WA livestock disease outlook – for vets summarises recent significant disease investigations by Department of Primary Industries and Regional Development (DPIRD) vets and private vets that contribute to that surveillance evidence.

Bench aids, livestock biosecurity resources, networking opportunities at Woolorama

Private vets are invited to join DPIRD vets to speak to producers at Wagin Woolorama in 2019. 

With sheep producers and private vets from around the state visiting Wagin Woolorama in March each year, it is a great opportunity to catch up with DPIRD and other veterinary colleagues and clients.

Private vets are invited to join DPIRD field vets Anna Erickson and Kristine Rayner and toxicology and residues expert Martin Matisons in the DPIRD shed (opposite the ram pavilion) on Site 626, Kitchener Street, to obtain copies of the latest DPIRD resources and to talk to producers about:

• managing biosecurity and preventing livestock disease resulting from dry season feed challenges
• surveillance incentives and subsidies for vets and producers, and
• how to prevent livestock residues and poisoning from occurring.

As well as an array of current livestock biosecurity factsheets, DPIRD will have a variety of laminated post-mortem bench aids available for vets to take away, including a new pig post-mortem bench aid.

If you would like to join Anna, Kristine and Martin in the shed in a rostered spot to speak to producers visiting Woolorama, please call Anna on 9881 0211 or email anna.erickson@dpird.wa.gov.au for details. Alternatively, you can drop in at any time to have a chat.

Wagin Woolorama will be held on Friday and Saturday, March 6-7.

Recent disease investigations

Illthrift and deaths in goats

• In a herd of 50 mixed aged Boer goats, six had died over a nine-month period and one was clinically affected, with all animals showing progressive weight loss and weakness.
• The animals had been purchased nine months prior, and were reported to be up to date with worming but had not received any recent vaccinations.
• Faecal worm egg counts from two does showed a moderate strongyle parasite burden, and blood tests of two kids showed glutathione peroxidase levels of 17 and 14 U/g Hb indicating a marked selenium deficiency. No deficiency was detected in the older goats.
• A faecal PCR for Johne’s disease (reportable) was negative.
• Selenium deficiency is more likely to occur in young, growing animals on deficient soils, and in higher rainfall regions. Selenium injections or drenches can be used to treat a deficiency and there are selenium-containing ruminal pellets, fertilisers, licks and blocks available to supplement a herd or flock. Exercise caution as overdosing can readily occur if animals are supplemented from multiple sources.
• See our webpage for more information about selenium deficiency in sheep.

Lumpy skin disease ruled out in case involving skin lesions in cattle in the South-West

• Multiple skin masses were identified on the head and forequarters of four cattle at slaughter. The masses were growing out from the skin and had rounded, rough surfaces ranging from 5–25mm in diameter. Lymph nodes appeared normal.
• The abattoir contacted their local DPIRD field vet about the unusual lesions, and samples were sent to the DPIRD laboratory for further investigation. 
• Histopathology and electron microscopy confirmed the suspicion of papillomavirus and the exotic poxviral disease lumpy skin disease (LSD) was ruled out. LSD results in nodules that involve the entire cutis, however they can be prone to ulceration, and they can also form on mucosal areas where they may resemble warts.
• Bovine papillomatosis or cattle warts can be caused by a number of different bovine papillomaviruses which differ in the pattern of lesion presentation. It is normally a self-limiting condition and rarely occurs in animals over two years of age. Lesions on the mucosa can rarely develop into squamous cell carcinomas.
• Transmission of the virus between cattle can occur through direct contact, mechanically or via fomites.
• LSD is a reportable, vector-borne viral disease of cattle that causes relatively low mortality. However, the disease can cause animal welfare issues and significant production losses. Infection typically causes an acute disease with fever, depression and characteristic skin nodules. There may also be a marked reduction in milk yield as well as abortion in pregnant animals. Originally limited to Africa, LSD has spread rapidly throughout the Middle East, southeast Europe and Russia in recent years and the risk of introduction to Australia is increasing. Read more on LSD in the Emergency Animal Disease Bulletin no. 121.
• Vets are encouraged to call their local DPIRD vet whenever suspicious lesions such as these are found. Veterinary investigations in these cases may qualify for a rebate as they contribute to proof of freedom from LSD.

Image 1: Electron microscopy of round, 40–50nm particles consistent with papillomavirus virions

Image 2: Papillomas on the mandible of an affected cow

Image 3: Papillomas on the head of an affected cow

Transmissible spongiform encephalopathy (TSE) ruled out as a cause of neurological signs in cattle

• 36 cattle from a mob of 200 died within a four-week period, and five were affected with clinical signs that included recumbency, staggers, tremors and collapse when moved.
• New season hay had been brought in and fed to the cattle two months prior.
• DPIRD tested hay samples as well blood, vitreous humor, gastrointestinal contents and fresh and fixed tissues.
• No histological signs of TSE were detected in the brain tissues, while there was some protein leakage from meningeal blood vessels. An ELISA test for annual ryegrass toxicity (ARGT) was positive on rumen contents and the hay sample returned a high risk rating for ARGT. In conjunction with the clinical and histopathological findings, ARGT was the likely cause of disease.
• It is recommended that producers who buy in hay request a commodity vendor declaration that states the feed has been tested for ARGT and is low-risk.
• Producers and vets who submit appropriate samples of adult cattle and sheep with neurological signs may qualify for a rebate through the national TSE surveillance program as results from testing help to provide evidence of Australia’s freedom from TSEs.
• Equine vets may wish to share the current DPIRD Facebook post about reducing the risk of ARGT with clients.

Image 4: Post-mortem findings included a pale, swollen liver and congestion of kidney and lungs.

In summer, watch for these diseases:

Reportable disease in the spotlight

Lead poisoning in livestock

Ingestion of lead by livestock can result in poisoning of the animal and lead residues in animal products. To protect food safety and ongoing access to markets, producers and vets should be aware of the importance of preventing livestock from accessing sources of lead, and of the regulations regarding lead residues in animal products.

Even small amounts of lead ingested by livestock, in particular cattle, may result in dullness, blindness, tremors, staggering and acute death. Old lead batteries provide the most common source of lead toxicity on the farm, and animals may encounter them when foraging around farm dumps and sheds, especially when feed is in short supply. Livestock may readily ingest the lead due to its sweet taste, and in ruminants the lead may lodge in the forestomach, providing a reservoir that can cause persistently high levels of lead for months or years.

Risk factors:

• inquisitive younger animals with relatively smaller body size
• hungry stock
• reduced pasture cover may expose lead hazards previously unnoticed
• agistment on unknown land with unknown hazards.

Common sources of lead on-farm:

• lead batteries, especially if burnt or with old, brittle casings
• painted surfaces and paint tins
• sump oil
• grease and oil filters
• linoleum
• caulking, putty.

Lead residues in animal products

Western Australia has laws to manage harmful residues in livestock. These laws safeguard the public and market access by helping to ensure animals are not supplied if they contain residues in excess of the maximum residue limit (MRL). National Residue Survey (NRS) testing at abattoirs will detect animals with elevated lead levels. When notified of such residues, DPIRD officers will visit the property the animals originated from to determine the lead source, and to ensure that other affected/exposed livestock do not go for slaughter. These animals are quarantined for a minimum of 12 months, and must not be sold for slaughter during this period.

Prevention

Producers can prevent lead poisoning and residues by removing any potential source of lead from places where livestock could access it, and by securely fencing the areas where lead sources may be stored. When animals are clinically affected, early veterinary intervention is important to minimise losses of exposed stock. If a producer or vet suspects livestock have been exposed to lead they should contact a DPIRD vet so that exposed animals may be tested for residues.

For more information, contact your local DPIRD vet or see the lead poisoning webpage.

WA Livestock Disease Outlook highlights benefits of surveillance

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of particular livestock diseases. The WA livestock disease outlook – for vets summarises recent significant disease investigations by DPIRD vets and private vets that contribute to that surveillance evidence.

Feedback and subscriptions

We welcome feedback. To provide comments or to subscribe to the monthly email newsletter, WA livestock disease outlook, email waldo@dpird.wa.gov.au