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Japanese encephalitis virus detected in samples from piggeries

Guest Author, 28/02/2022
Pig and livestock owners are urged to be alert for signs of Japanese encephalitis in their animals, following the detection of Japanese encephalitis virus (JEV) in samples from multiple commercial piggeries in NSW, as well at one property in Victoria and another in Queensland.

NSW Department of Primary Industries (DPI) Chief Veterinary Officer Dr Sarah Britton said JEV does not present a food safety risk and all Australian grown pork remains safe to eat, however the virus does cause reproductive failures in pigs.

The Victorian Department of Health has also issued a notice stating that JEV is a rare but potentially serious infection of the brain caused by a virus spread to humans through mosquito bites.

No cases of JEV have been detected in humans, however several cases of encephalitis with no identified cause have been detected in NSW and SA in the past month.

“Most JEV infections are asymptomatic, however those with severe infection (less than one per cent) may experience neck stiffness, coma, and more rarely, permanent neurological complications or death.”

While there have been no confirmed infections in humans, there is a risk of transmission to humans and therefore the possibility of infection caused by JEV should be considered in patients with encephalitis.

JEV has however not been detected in mosquitoes in Victoria nor in other states at this point in time.

NSW Chief Veterinary Officer Dr Sarah Britton said the NSW DPI’s State Veterinary Diagnostic Laboratory and the Australian Centre for Disease Preparedness have confirmed the presence of the virus in samples submitted from farms at which animals showed symptoms last week,” she said.

“To date, the virus has been confirmed in samples from six properties in Western and Southern NSW, as well as at one Victorian property and one Queensland property through tests by those state agencies.”

The virus commonly circulates in mosquito populations in areas where it is endemic and can be transmitted to people and animals through the bites of infected insects, but is not transmitted from person to person or from animal to animal.

Horses and other livestock can also be infected through mosquito bites and NSW Health has issued advice to people in areas with high mosquito numbers to take extra precautions against being bitten.

“NSW DPI has initiated an Incident Management Team to lead an emergency response, in conjunction with other states and territories, and is working closely with NSW Health to minimise effects on industry and the community,” Dr Britton said.

Australian Chief Veterinary Officer Dr Mark Schipp it was the first time the virus has been detected in southern Australia, and biosecurity authorities are working with their human health departments to understand the implications and risks of human exposure.

“The Department of Health and the Department of Agriculture, Water and the Environment are collaborating closely, together with state and territory counterparts.

“We are meeting regularly and working together to work through the next steps of this situation.

“We’re asking anyone who works with pigs or horses, even if they’re a pet in the backyard, to keep an eye out for and report any possible signs of this disease.

“The most common symptoms in pigs are mummified or stillborn piglets, or piglets who show neurological problems in the first six months of life. The disease tends to be asymptomatic in adult sows, but boars can experience infertility and testicle congestion.

“Horses can experience a range of symptoms. While most infected horses do not show signs of disease, some more severe signs of JEV in horses include fever, jaundice, lethargy, anorexia and neurological signs which can vary in severity.

“JEV is a nationally notifiable disease, which means if you suspect an animal is showing signs of the disease, you must report it (see contact details below). Measures should also be taken to protect animals from mosquitoes – for instance, applying a safe insect repellent and putting a summer rug on horses.”

Acting Chief Medical Officer Dr Sonya Bennett said JEV infections can be contracted by humans through the bite of a mosquito. There are no confirmed human cases in Australia at this stage, although this is under active investigation. “We are aware that several cases of encephalitis of unknown cause have been identified in New South Wales, Victoria and South Australia within the past month.

“JE is also a notifiable disease in humans and health authorities across the country are on the alert for human cases and are in direct contact with people associated with the affected piggeries” Dr Bennett said.

“Pigs are the focus from a human health perspective as they can infect mosquitoes who then infect humans. This is not the case with horses.

“Severe illness arising from JEV infection in humans is rare and most people will have no symptoms at all if infected.

“However, a very small proportion of people infected may develop a serious illness such as encephalitis and experience symptoms including neck stiffness, severe headache and coma, and more rarely, permanent neurological complications or death.

“Encephalitis is the most serious clinical consequence of JEV infection. Illness usually begins with symptoms such as sudden onset of fever, headache and vomiting.

“Anyone experiencing these symptoms, particularly if they’ve visited regions in eastern Australia or South Australia where there has been high mosquito activity, should seek urgent medical attention.

“Clinicians should be aware of the possibility of infection caused by JEV in patients in affected areas with encephalitis and refer people for appropriate testing, after other common causes have been excluded.

“There is work underway to plan for targeted vaccinations. Two different vaccines are available for protection against JEV in Australia and are very safe and effective for both adults and children.

“However, prevention is always better than a cure and there are simple steps we can all take to avoid our exposure to infected mosquitos.

“People in areas of high mosquito activity in Eastern Australia should use mosquito repellent containing picaridin or DEET on all exposed skin.

“Wear long, loose fitting clothing when outside, and ensure accommodation, including tents, are properly fitted with mosquito nettings or screens.

“We will continue to meet with health authorities in the states and territories to progress the public health response to this disease.”

Livestock owners are encouraged to be alert to the signs of JE. These include reproductive failure in pigs, with 50–70pc losses reported in affected populations:

  • Pregnant sows and gilts may abort, produce mummified or malformed foetuses, or give birth to stillborn or weak piglets at term,
    Infertility in boars – this is most commonly temporary but may be permanent if the boar is severely affected.
    Nervous signs such as tremors and convulsions are occasionally seen in pigs up to 6 months of age.
  • If you suspect JE in pigs or other livestock, you must report it to the 24-hour Emergency Animal Disease Hotline on 1800 675 888.

Sources: DAWE, NSW DPI, Vic Dept of Health. More information on JEV is available from www.dpi.nsw.gov.au/jev and information on human health effects is available from www.health.nsw.gov.au. More information from the Victorian Department of Health here

To report suspected JEV in pigs or other animals, contact your local veterinarian or call the national Emergency Animal Disease Watch Hotline on 1800 675 888For more information on JEV in animals on the DAWE website, visit https://www.outbreak.gov.au/current-responses-to-outbreaks/japanese-encephalitis

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