Unprecedented Outbreak: Japanese Encephalitis Virus Strikes Australian Pig Farms

In February 2022, southeastern Australia was rocked by an unexpected outbreak of Japanese encephalitis virus (JEV), causing widespread devastation in the region’s pig-producing sector. Veterinarians quickly identified alarming clinical signs across multiple piggeries, signaling the urgent need for action.

Chris Richards from Apiam Animal Health in Australia highlighted the diverse range of symptoms observed, including prolonged gestation periods, stillborn and mummified piglets, congenital abnormalities, and neurological issues. What made this outbreak particularly concerning was the geographic spread of affected farms, with some separated by thousands of kilometers.

The confirmation of JEV in southeastern Australia prompted an immediate response, treating it as a foreign animal disease (FAD) outbreak. Over the following months, more than 80 piggeries reported confirmed cases, indicating the severity of the situation.

Among the most distressing symptoms was the extended gestation periods experienced by some sows, leading to the birth of mummified and stillborn piglets. This phenomenon affected varying percentages of piglets in each litter, with a strong correlation observed between serologically positive sows and mummified piglets.

Congenital abnormalities in stillborn piglets further added to the complexity of the outbreak, with severe conditions like arthrogryposis and brachygnathia being observed. Neurological abnormalities, including cerebral and cerebellar aplasia, hydranencephaly, and congenital tremors in live-born piglets, painted a grim picture of the virus’s impact.

JEV, a flavivirus endemic to eastern and southeastern Asia, had never before been detected in southeastern Australia. Waterbirds serve as its reservoirs, with pigs acting as amplification hosts. Although humans and horses can contract the virus, they are considered dead-end hosts.

Despite the unprecedented nature of the outbreak, the Australian pig industry’s response was swift and coordinated. Previous planning for exotic animal diseases, coupled with strong partnerships between producers and government officials, facilitated a robust response to this unforeseen threat.

The emergence of Japanese encephalitis virus in Australia serves as a stark reminder of the ongoing challenges posed by zoonotic pathogens and the critical importance of preparedness and collaboration in mitigating their impact.