Australian horse owners warned of Japanese encephalitis outbreak

A common banded mosquito, Culex annulirostris female.
A female common banded mosquito, Culex annulirostris. © Stephen L. Doggett/Department of Agriculture, Water and the Environment

Australian biosecurity officials are urging horse owners in several states to implement mosquito control measures to help protect their animals amid an outbreak of Japanese encephalitis.

The mosquito-borne virus, which can infect horses, pigs, and humans, has been confirmed in pigs in Victoria, New South Wales, Queensland, and South Australia. There have also been confirmed cases in humans.

The outbreak has been declared a Communicable Disease Incident of National Significance and as a nationally notified disease, must be reported to biosecurity authorities.

Waterbirds act as natural reservoirs for the virus, and mosquitos can spread Japanese encephalitis virus (JEV) to horses, pigs and other animals. It can cause reproductive losses and encephalitis in pigs and horses.

Australia’s Department of Agriculture, Water and the Environment is working with the Department of Health, and state and territory counterparts, to respond to the outbreak.

Anyone living, working or spending time near pigs or waterways where waterbirds are present should take steps to avoid being bitten by mosquitoes.

Horses are a “dead-end host” – meaning mosquitos cannot pass the virus from horses to humans. Rugging and hooding horses with a lightweight summer rug and fly mask can help protect against mosquito bites. Stabling horses between dusk and dawn may also be beneficial as the mosquito that transmits JE feeds at night and is reluctant to enter dwellings. If the horse allows, apply a safe insect repellent.

Most cases of Japanese encephalitis in humans are asymptomatic, but those with severe infection may experience neck stiffness, coma, and more rarely, permanent neurological complications or death. Illness usually begins with a sudden onset of fever, headache and vomiting.

There are no treatments for humans with Japanese encephalitis but symptoms can be relieved with rest, fluids and taking paracetamol for pain or fever. In more severe cases, hospitalisation for supportive care and close observation may be required.

Culex annulirostris.
Culex annulirostris. Photo by John Tann

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