WA Livestock Disease Outlook - for vets

Japanese encephalitis virus detected in Australian pigs

Japanese encephalitis (JE) has recently been detected in piggeries in Victoria, New South Wales, Queensland and South Australia. There are no confirmed detections in Western Australia (WA) and imports of live pigs to WA have been temporarily suspended. Movement controls have also been implemented for importation of pig semen into WA.

JE is an acute mosquito-borne viral disease that can cause reproductive losses and encephalitis in susceptible species. Pigs and horses are the most commonly affected animal species, but JE virus is zoonotic and can pose a serious risk to human health.

The most common clinical signs of JE in pigs are reproductive losses including abortions, mummified foetuses and stillborn or weak piglets. Tremors and convulsions are occasionally seen in pigs up to six months of age.

In horses, most clinical disease is mild and may be unrecognised, however fever, decreased or no appetite, lethargy, ataxia and incoordination may occur. Some horses may die

WA pig producers and horse owners are urged to monitor for signs of JE and report any suspect signs to a local private veterinarian, DPIRD veterinary officers or the national Emergency Animal Disease Watch Hotline on 1800 675 888. Cases of suspect JE in pigs or horses are eligible for a Significant Disease Investigation (SDI) subsidy.  Some additional epidemiological information needs to be collected – please discuss with your DPIRD Field Veterinary Officer.

More detail on Japanese encephalitis in animals is available here.

Australian Pork Limited evidence of absence project

In 2018, Australian Pork Limited developed a project aimed at increasing the evidence of absence of important exotic pig diseases (vesicular diseases not included) by encouraging exclusion testing for clinically relevant pig morbidity and mortality cases.  In general, from the inception of the project to the end of the reporting period, there was a very significant increase in evidence of absence (Final report available here). 

Due to the success of the first project, a second project has been relaunched over a longer timeframe (July 2021-July 2024).  Veterinarians called to investigate the following clinical syndromes in pigs are encouraged to contact Dr Diana Turpin (WA Project Contact) on 0457 020 120:

• Sow abortion and stillbirths, sporadic or abortion storms
• Piglet diarrhoea, vomiting and mortality
• Piglet respiratory disease, high case mortality
• Weaner central nervous signs, fever and anorexia
• Weaner central nervous signs and respiratory disease 
• Weaner and adult diarrhoea, high morbidity
• Fever in grower pigs

Recent livestock disease investigations

Neurological signs and sudden deaths in young merino ewes in the Wheatbelt

• Five of 480 Merino weaner ewes died on a property in December, with a further seven displaying neurological signs including seizures and foaming at the mouth.
• The sheep had been grazing fresh oat stubble and were also getting 500g of lupins per head every other day. The vaccination status of the mob was unclear. There was no note of clinical signs when they moved into the paddock.
• The producer contacted their local DPIRD field veterinary officer who visited the property to conduct a disease investigation.
• Post-mortems were performed on two ewes but did not show any significant lesions grossly. The veterinarian submitted a full sample set, including the brain, to the DPIRD laboratory for analysis.
• Differentials for sudden death and neurologic signs in sheep include enterotoxaemia, hypocalcaemia, scrapie (reportable), annual ryegrass toxicity, cyanobacterial toxicosis, plant poisonings, and lead poisoning (reportable).
• Testing of the rumen contents and faeces was positive for annual ryegrass toxin on ELISA, with high levels of toxin detected. Histopathology of one sheep showed marked pulmonary oedema and diffuse periacinar hepatic degeneration. It is possible the liver change was due to hypoxia caused by the pulmonary oedema, which itself may have been caused by the very high dose of toxin detected or was neurogenic in origin. No brain lesions were observed, however very acute toxic effects are not always seen as morphological changes.
• In conjunction with consistent clinical signs and significant pulmonary oedema on histology, ARGT was deemed the cause of disease in this flock.
• It was recommended that animals on low to moderate risk feed should be observed daily, and those on high-risk feed or paddocks should be carefully moved to safe feed sources.
• Testing of ryegrass in pasture can be used to identify safe paddocks, and to detect the bacteria early so exposure can be managed. See the Testing for ARGT webpage for more details.
• Lead toxicity was excluded in this case. Lead ingestion by food-producing animals presents a risk to human food safety, and to access to export markets. Suitable samples for lead testing are whole blood and fresh kidney.
• It is important to investigate neurological disease or sudden deaths in livestock, to ensure they are not due to an exotic disease with similar signs. Investigations may be eligible for subsidies under several surveillance incentives.  

Close-up of ryegrass

Haemorrhagic septicaemia rule out in cattle in the South-West

• Two 18-month-old Angus heifers out of a herd of 80 had been found dead overnight in a property in the southwest. One week prior, there was a separate similar death, and another heifer who had experienced respiratory signs on the property had since improved.
• The herd had been on oaten hay since their arrival approximately one month earlier. The herd had been given a primary vaccine against mannheimiosis and drenched previously.
• The producer contacted their local DPIRD field veterinary officer who visited the property to conduct a disease investigation.
• On post-mortem, there was a copious straw-coloured pleural effusion and cranioventral consolidation of the lungs. There was evidence of autolysis as the abomasal mucosa was friable and the rumen mucosa was sloughed.
• Histopathology of the lungs showed marked bronchopneumonia characterized by large amounts of fibrin, alveolar necrosis and haemorrhage. Cultures of the lung and the pleural fluid grew Pasteurella multocida. Testing for ARGT, a range of respiratory viruses, and listeriosis was all negative.
• Further in-house testing of the P. multocida isolate excluded the serotype that is responsible for the exotic and reportable disease, haemorrhagic septicaemia.
• Haemorrhagic septicaemia is a highly fatal, significant disease of cattle and buffalo in tropical and subtropical regions. Most cases are acute or peracute and the clinical signs include sudden severe pyrexia, dyspnoea, salivation, hot and painful oedematous skin swellings, and submucosal petechiation.
• If you investigate a disease in which you are suspicious of an exotic disease you must contact your local DPIRD field veterinary officer or the emergency animal disease hotline on 1800 675 888.

Private veterinarian investigates neurologic signs and deaths in weaner pigs in the South-West region

• Out of 14 recently acquired 12-14 week old Duroc piglets, two presented with neurological signs including dog sitting, collapse and generalised tremors. Pyrexia was also noted.
• A private veterinarian notified DPIRD of the case after treatment with antibiotics was not successful. Vaccination history of the recently introduced weaners was not known.
• The private veterinarian performed post-mortem examinations on both weaner pigs and submitted samples to DPIRD’s Diagnostic and Laboratory Services (DDLS) for laboratory analysis.
• Histopathology of the brain revealed a significant suppurative meningitis which was most likely associated with a bacterial infection. No identifiable bacteria were seen on Gram-stained sections of the brain. Initial testing at the Australian Centre for Disease Preparedness (ACDP) indicated that Japanese encephalitis was not present in these pigs, and further testing is underway.
• Bacterial meningitis in young pigs is typically associated with either Streptococcus suis or Glaesserella (formerly Haemophilus) parasuis. Culture of either bacteria is required to confirm the diagnosis (fresh brain tissue was not submitted). 
• Veterinarians are encouraged to call their local DPIRD veterinarian whenever an emergency animal disease is suspected to discuss sample collection. 
• Streptococcus suis can be carried in the tonsils of carrier pigs and passed onto other pigs.
• Glaesserella parasuis is the commensal, bacterial agent responsible for Glasser’s disease, in which acute infection can cause polyserositis, arthritis and meningitis. Treatment of Glasser’s disease involves the use of antibiotics but it needs to be treated early in order to be effective. Vaccination is also available depending on the serovar.
• The onset of both S. suis meningitis and Glasser’s disease may be associated with exposure to stress from husbandry procedures, transport or introduction to a new environment. Prevention strategies for both diseases involves minimising stress in young pigs.
• Introduced pigs present the greatest risk of introducing disease to a herd.  It is recommended that producers only buy stock from a single herd with a higher or comparable health status.  All new stock should be inspected upon arrival and regularly thereafter. 
• Testing for the reportable diseases Aujeszky's disease, classical swine fever and African swine fever was negative by PCR.
• There are many emergency infectious diseases of pigs that do not occur in Australia. Keeping Australia free from these diseases is vital to help protect human/animal health, livestock production and continue to allow export market access.

Piglets huddling

Group of piglets

Diseases to watch out for in late Summer / early Autumn

Note: Always include base samples and any clinical or gross lesions in submissions. For sample submission advice, contact your DPIRD field veterinary officer or the duty pathologist on +61 (0)8 9368 3351.

DPIRD nationally notifiable disease investigations (October – December 2021)

Nationally notifiable diseases pose a significant threat to animal industries and animal health in Australia and to international export market access. When DPIRD receives samples from disease investigations where animals are displaying signs of disease similar to a notifiable disease, we undertake testing. Data from these investigations help provide evidence that our State is free from important diseases and supports our access to markets.

In the last quarter of 2021 (October-December), DPIRD tested for nationally notifiable diseases in 174 disease submissions. From these 174 submissions, DPIRD’s laboratory undertook 280 nationally notifiable disease tests.

Figure 1: Number of national notifiable disease tests of domesticated animals with visible disease signs undertaken by DPIRD (October to December 2021)

In 2021, DPIRD carried out over 1000 nationally notifiable disease tests on more than 650 submissions to investigate disease in animals with visible disease signs. (This does not include notifiable disease tests for export testing or general surveillance in well animals.) The most common nationally notifiable diseases investigated in 2021 in livestock are shown below.

Figure 2: The top 10 nationally notifiable diseases tested for in DPIRD laboratory submissions from livestock with visible disease signs. The dark bars represent the number of investigations during October to December 2021. Note that Department of Agriculture, Water and the Environment also submits potential TSE cases (scrapie and BSE) to Australian Centre for Disease Preparedness separately.

Other news

Management of Johne’s disease in Western Australia

Following the detection of Johne’s disease (JD) cattle strain (C-strain) in cattle in Western Australia, the WA cattle industry have agreed JD (C-strain) was not technically feasible or economical to eradicate. Consequently, regulation of JD in WA has been reduced and, in consultation with the relevant industries, WA’s livestock import conditions have been amended to reflect this. The new conditions came into effect on 17 January 2022.

All livestock moving into WA from interstate that are not going immediately to slaughter must meet the following requirements:

• All properties the livestock have resided on must have had no suspected or confirmed JD infection in any species of livestock during the five years prior to movement of the livestock (to be moved into WA) off the property(ies).
• The livestock to be moved into WA must not have had contact with livestock suspected or known to be infected with JD.
• Cattle vaccinated for JD must be identified with a three-hole punch (preferably administered in the outer third of the right ear) and recorded in the National Livestock Identification System as JD vaccinated.

Further information can be found on the agric.wa.gov.au website on the webpage: Forms for importing livestock into WA. You can now watch a recorded presentation on JD and biosecurity planning via a link on the webpage: JD in cattle: management in WA.

Please contact your local DPIRD field veterinary officer if you require more information.

WA Livestock Disease Outlook highlights the 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 veterinarians summarises recent significant disease investigations by DPIRD veterinarians and private veterinarians that contribute to that surveillance evidence.

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