Australian health officials raise virus alarm, concerns for pig and mosquito transmission

By Melissa Coade

March 4, 2022

A pig
Chief veterinary officer Dr Mark Schipp told pig producers to remain vigilant for signs of the disease among animals. (yairventuraf/Pixabay)

A potential Japanese encephalitis virus (JEV) outbreak, with the virus detected in 14 piggeries across NSW, South Australia, Queensland and Victoria, will require national response according to top officials who have already briefed the national security committee of cabinet.

In an official declaration document, health officials explained JEV was a mosquito-borne viral disease that mostly occurs in pigs and horses. JEV can cause disease in people and, in some rare cases, other animals. 

“Pigs are the focus from a human health perspective as they can infect mosquitoes that can then infect humans. This is not the case with horses,” the official document said. 

“Humans can become infected with JEV through the bite of an infected mosquito. 

“The virus cannot be transmitted between humans, and it cannot be caught through eating pork or pig products.”

The federal health department is currently investigating cases of encephalitis of unknown origin across different states across Australia, testing for arboviral diseases, including JEV.

On Thursday evening Queensland health officials confirmed that a case of human JEV had been verified and was being treated in Brisbane hospital. The patient had recently travelled in regional parts of the state’s south.

In a joint statement on Friday, acting chief medical officer Dr Sonya Bennett and chief veterinary officer Dr Mark Schipp said the unfolding situation has been officially deemed a communicable disease incident of national significance.

The decision was made in consultation with experts of the Australian Health Protection Principal Committee.

Bennet said health policy interventions and public messaging was needed to handle the risk. A national communicable disease working group has been established with vaccine and arbovirus experts to support the national response.

“The Australian government’s health and agriculture departments are working very closely with their state government counterparts to ensure a swift and coordinated response,” the acting chief medical officer said.

“[Co-orindated measures will] include mosquito surveillance and control measures and identification of those at direct risk, and for the rollout of vaccines. Public health communications regarding mosquito protection will target affected communities,” she said.

A communications campaign to educate the public about JEV symptoms such as neck stiffness, severe headache and coma, as well as the precautions that should be taken is being developed. 

Less than 1% of people who are infected with JEV may develop a serious illness such as encephalitis.

The vast majority of infected people will show mild or no symptoms at all. 

Australia’s chief veterinary officer Dr Mark Schipp told pig producers to remain vigilant for signs of the disease among animals. Signs of JEV in pigs such as stillborn or weak piglets, or an impaired nervous system were all things to watch for. Adult sows however did not typically show symptoms.

For horse owners, signs of JEV are also difficult to detect but can include an elevated temperature, jaundice, lethargy or anorexia. Lack of coordination, difficulty swallowing, impaired vision or over-excitement may also present as symptoms in horses.

“People working with pigs, even if they’re only a backyard pet or a small herd, should take steps to control mosquitoes, as well as continuing to practice good biosecurity,” Dr Schipp said.

“Horse owners can also put measures in place to help their horses avoid mosquito bites, including using hooded rugs, fly masks, and applying a safe insect repellent.”

Producers should report unexplained pig abortions or stillbirths, Dr Schipp added.

“If you suspect an animal is showing signs of the disease, you must report it via your local veterinarian or the national Emergency Animal Disease Watch Hotline on 1800 675 888,” he said.


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