Mosquito-borne Murray Valley Encephalitis Virus found in South Australia

The Department for Health and Wellbeing acting executive director of health protection Dr Fay Jenkins said a sentinel chicken, one of five chickens in a surveillance flock based near Meningie, in South Australia, has tested positive to both Murray Valley Encephalitis Virus (MVEv) and Kunjin virus.

"We know there has been an increase in the number of mosquitoes present along the Murray River this season, however, the detection of MVEv and Kunjin virus is an even stronger reminder for all South Australians to be vigilant in their fight against mosquito bites," Dr Jenkins said.

"Many people infected with MVEv are asymptomatic, or have mild symptoms such as fever, headache and nausea.

"Although only a few people who become infected with MVEv will develop more serious symptoms which may include confusion, headaches, neck stiffness, tremors, drowsiness and seizures, for those who do, it can be very serious and is fatal in about 20 per cent of cases.

"For those who survive, about 40 per cent of people will suffer permanent neurological damage."

There is no vaccine and no cure for mosquito borne diseases transmitted in South Australia and the only way of preventing disease is to avoid being bitten by mosquitoes.

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"To protect against mosquito borne diseases, we are encouraging people to 'fight the bite' and take precautions such as wearing long, loose-fitting, light coloured clothing and use a repellent which contains DEET or picaridin," Dr Jenkins said.

"People should also reduce the risk of being bitten by mosquitos by proofing their homes and by removing any potential breeding sites on their properties."

As part of SA Health's mosquito borne disease monitoring program, six flocks of sentinel chickens are maintained in strategic locations along the Murray River and are routinely tested for viruses spread by mosquitoes.

All other flocks of sentinel chickens based along the Murray have tested negative for these viruses to date, however, several chickens in the Ramco flock near Waikerie tested positive to MVEv and KUNv in March 2020. This was the first time that sentinel chickens in South Australia had tested positive to these viruses since 2011.

Chickens provide a good indicator of the risk of mosquito borne diseases in the community, as they readily produce antibodies to viruses which can also infect humans without developing symptoms of those diseases. These chickens cannot pass the infection on to humans.