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.

[1]

Private vets assist in ehrlichiosis surveillance

The exotic dog disease, ehrlichiosis, was detected in Australia for the first time this year in the Kimberley, Pilbara and Gascoyne as well as the Northern Territory. The disease is spread by the bite of an infected brown dog tick, which is common across the north of Australia.

Ehrlichia canis is a nationally notifiable disease, which means suspicion of this disease must be reported to a DPIRD vet [2].

Surveillance has shown the disease is established in the Kimberley, with sampling and testing now targeted to dogs in the Pilbara and Gascoyne. DPIRD would like to acknowledge the valuable assistance provided by private vets in surveillance for the disease.

DPIRD asks vets to remind dog owners in northern WA and travellers to and from northern WA to:

ensure their dogs are on an ongoing effective tick treatment
check their dogs daily for ticks
report signs of ehrlichiosis to a vet.

People moving their dogs south out of the Kimberley, where the disease is established, must fill out a form to notify DPIRD and only move the dog if it is healthy and on a tick treatment.

Recent livestock disease cases in WA

Neurological horse tests negative for exotic and reportable diseases

A private vet examined a four-year-old horse with a five-day history of hindlimb ataxia, muscle tremors and hypersensitivity to stimuli. Samples were submitted to DPIRD under the Significant Disease Investigation program [4].
Feed, faecal and blood samples were submitted with a provisional diagnosis of annual ryegrass toxicity (ARGT) [5].
Exotic and reportable viral diseases that can cause neurological signs in horses were tested for, including eastern equine encephalitis, western equine encephalitis, Venezuelan equine encephalitis, equine herpesvirus-1 (abortigenic and neurological strains), Hendra virus [6] and rabies [7]. Negative test results support WA’s claims to freedom from these diseases.
The reportable diseases Australian bat lyssavirus [8], West Nile (Kunjin) virus, Murray Valley encephalitis, flavivirus and Ross River virus were ruled out in addition to the exotics listed above.
Blood testing showed antibodies to equine herpesvirus-4, which is widespread in horses in WA. EHV-4 is preventable by vaccination. It usually causes mild respiratory illness, and so was unlikely to be contributing to disease in this horse.
A quantitative ARGT ELISA test on one hay sample returned a result of ‘high risk’ for toxicity, and an ELISA of the faeces was positive for the ARGT corynetoxin. Given the neurological signs in the horse, a diagnosis of ARGT was considered probable, and it was recommended that animals be removed from the high-risk feed.
The risk of ARGT in livestock is reduced by inspecting animals daily for neurological signs, and by requesting a vendor declaration when purchasing hay [9].

Salmonellosis causes deaths in cows and calves

Between April and June, DPIRD detected 10 cases of salmonellosis in cattle [10] and sheep [11]. The most common clinical signs were diarrhoea, fever and sudden death.
In one case, DPIRD investigated deaths in first calving heifers. Five heifers had died from a group of 130 over the course of a week. One mature cow had also died from a group of 70. Some of the cows had severe diarrhoea.
A post-mortem of one heifer showed marked abomasal mucosal inflammation. A full set of fresh and fixed tissues, gastrointestinal contents and faecal samples were submitted to DPIRD [12] laboratories.
Salmonella Typhimurium was identified in the ileal contents and faecal samples. Additionally, liver assay showed a low copper level, which can result in poor growth and ill-thrift, diarrhoea, hypopigmentation of the coat, bone fragility and anaemia.
Susceptibility to Salmonella infections can be reduced by minimising ivestock stressors where possible such as mustering and yarding. Good nutrition, parasite control, and management practices that eliminate long periods without feed and water will minimise the risk of Salmonella outbreaks.
There are a number of serovars of Salmonella that are reportable in WA: S. abortus ovis in sheep, S. abortus equi in horses, and Salmonella enteritidis and S. pullorum in poultry.
Salmonella is also a zoonosis, so producers and veterinarians should take steps to protect themselves from infection when handling animals with suspected salmonellosis.

In winter, watch for these livestock diseases

Disease, typical history and signs	Key samples
Calf diarrhoea/scours Affects young calves and is usually caused by a combination of predisposing environmental conditions and infectious organisms. Newborn calves that received a good supply of colostrum from their dams will be better protected. Signs include depressed appearance; white, yellow, grey or blood-stained diarrhoea; dehydration; recumbency; and death. Calf scours may be caused by single or multiple organisms. Some common organisms include bovine coronavirus, rotavirus, coccidia, E. coli, Salmonella and Cryptosporidium. Cows can be vaccinated against a number of these before calving. DPIRD’s calf scours webpage [13] outlines a number of strategies to prevent and treat an outbreak.	Ante-mortem: 10mL faecal sample (chilled) from 5 affected animals if possible
Listeriosis Caused by the zoonotic bacteria Listeria monocytogenes. Sources of infection include spoiled silage, rotten vegetables, contaminated soil or where asymptomatic animals (including rodents) have shed the bacteria in their faeces and in spoiled feed. Livestock that consume contaminated feed material can be infected via damage to the oral mucosa caused by rough feed. Silage should be properly prepared and leftover feed cleared away promptly to prevent spoilage. Key signs include neurological signs such as circling (due to encephalitis), recumbency and deaths. May cause abortions [14] 5-6 weeks prior to lambing, stillbirths or newborn lamb deaths.	Ante-mortem: Cerebrospinal fluid Post-mortem: Fixed brain, fresh spinal cord and liver, brain stem swabs If neurological signs are present, discuss with your DPIRD vet [2]subsidies for TSE testing

Disease, typical history and signs

Key samples

Calf diarrhoea/scours

Affects young calves and is usually caused by a combination of predisposing environmental conditions and infectious organisms. Newborn calves that received a good supply of colostrum from their dams will be better protected.
Signs include depressed appearance; white, yellow, grey or blood-stained diarrhoea; dehydration; recumbency; and death.
Calf scours may be caused by single or multiple organisms. Some common organisms include bovine coronavirus, rotavirus, coccidia, E. coli, Salmonella and Cryptosporidium. Cows can be vaccinated against a number of these before calving.
DPIRD’s calf scours webpage [13] outlines a number of strategies to prevent and treat an outbreak.

Ante-mortem:

10mL faecal sample (chilled) from 5 affected animals if possible

Listeriosis

Caused by the zoonotic bacteria Listeria monocytogenes. Sources of infection include spoiled silage, rotten vegetables, contaminated soil or where asymptomatic animals (including rodents) have shed the bacteria in their faeces and in spoiled feed.
Livestock that consume contaminated feed material can be infected via damage to the oral mucosa caused by rough feed. Silage should be properly prepared and leftover feed cleared away promptly to prevent spoilage.
Key signs include neurological signs such as circling (due to encephalitis), recumbency and deaths. May cause abortions [14] 5-6 weeks prior to lambing, stillbirths or newborn lamb deaths.

Ante-mortem:

Cerebrospinal fluid

Post-mortem:

Fixed brain, fresh spinal cord and liver, brain stem swabs
If neurological signs are present, discuss with your DPIRD vet [2]subsidies for TSE testing

[15]

Have your say on the future management of Johne’s disease (C-strain) in cattle in WA

The Cattle Industry Funding Scheme Management Committee (IFSMC) is calling for submissions from the WA cattle industry on the future management of Johne’s disease (C-strain) in cattle in WA.

Western Australian beef, dairy and stud producers, industry bodies, exporters, livestock agents, processors, transporters, veterinarians and government agencies are invited to have their say.

Following national deregulation of Johne’s disease (JD) in cattle in 2016, the WA cattle industry requested continuing state regulation of JD (C-strain) in cattle. Cattle IFSMC funded a control program that included targeted surveillance for JD (C strain) in cattle in WA to establish WA’s current JD (C-strain) status. The completed surveillance showed there was a very low risk of the disease being present in WA cattle.

The WA cattle industry, through the Cattle IFSMC, is now being asked to decide whether JD (C-strain) in cattle continues to be managed through state regulation and, if so, under what conditions – or is deregulated and individual stakeholders manage their own biosecurity to prevent and manage JD on their properties.

There are several options to consider, and industry members are encouraged to read the consultation paper and view the webinar [16] before making a submission on their preferred option. The consultation closes on 2 September 2020.

For more information and to make a submission, see the consultation webpage [16].

Following the close of the consultation, the Cattle IFSMC will convene a meeting with industry representatives to consider the submissions and facilitate a decision by industry.

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.

We welcome feedback. To provide comments or to subscribe to the monthly email newsletter, WA livestock disease outlook, email waldo@dpird.wa.gov.au [17].