An unknown virus moved through David Refalo’s sow herd in New South Wales, Australia, last Christmas. He had 30 piglets die out of 170 total piglets. Tests showed nothing.
“Piglets would lose condition at five days old and die quickly,” says Refalo of Refalo Free Range Pork. “Piglets weren’t responsive to antibiotics. We’ve had two batches since then that were fine, and our last batch had seven sows total abort with some piglets dying at a few days of age.”
Less than an hour away, Paul and Emma Baxter started noticing an increase in stillborns and piglets displaying signs of neurological damage (shaking) during the first week of January at their 200-sow farrow-to-finish operation in west central New South Wales.
“Being the middle of summer in Australia, stillborns aren’t uncommon due to heat so we overlooked it at that point,” says Paul Baxter of Riverdale Farm. “We farrow about 10 sows a week. Since the first week of January, we’ve seen fairly consistent litter losses of three full litters a week (30%).”
It took a long time, but a diagnosis finally came in for both farms: Japanese encephalitis virus (JEV).
“It’s the worst disease or virus I’ve experienced in 19 years of pig farming,” Refalo says. “It reminds you of how fast things can change with livestock.”
What is JEV?
JEV is a flavivrus in the same family as West Nile virus, St. Louis encephalitis virus, and Murray Valley encephalitis virus. The virus is maintained in a cycle between mosquitoes and vertebrate hosts, mainly ardeid birds such as herons, egrets and bitterns. There is spillover of JEV to other species including pigs, humans, horses and other domestic animals. Humans and horses are considered dead-end hosts because they usually do not develop high levels of viremia, while pigs are an amplifying host.
During a Swine Health Information Center webinar, Kirsty Richards, DVM, a veterinarian with SunPork Group in Australia, noted human cases have been diagnosed–with some mortalities–in Australia as well as cases of reproductive and neurological disease in pig herds.
Experts say clinical presentation varies by age and prior exposures in pigs. For adult pigs, it is primarily a reproductive disease, though affected adults may present with a non-specific fever. Sows can exhibit abortion, stillborn, fetal mummification, or subsequent production of weak piglets. Boars exhibit orchitis and infertility. In piglets, non-specific signs and wasting are evident as are neurologic disease and high mortality.
Bernie Gleeson, Richards’ colleague at the SunPork Group, shared in the webinar how aborted litters had fetuses with domed heads, subcutaneous oedema, ascites, and arthrogryposis. Necropsy of aborted piglets revealed the absence of forebrain, hindbrain, and cerebellum. Some affected piglets born alive were shaky with poor survival.
Flooding caused an influx of mosquitoes at Riverdale Farm. Photo by Paul and Emma Baxter.
An Emotional Toll
These heavy losses are tough on a family-run farm with no employees. Baxter says it has taken a toll on his family – emotionally and financially.
“On top of the financial pressures that come with losing 30% of farm turnover and additional restrictions implemented, government departments stopped movements of everything at the start including semen, breeding stock and sale pigs for the first two weeks,” Baxter says. “Picking up around 40 stillborn and mummified piglets a week for 13 weeks gets depressing.”
Shaun Blenkiron, a Hampshire pork producer in South Australia, says his herd has avoided JEV so far because it is very dry around his farm and mosquitoes are at a minimum. There have been around four cases in his state of South Australia, but all have been along the Murray River which is located about one hour from his farm.
“The stories I’ve been told are like nightmares,” Blenkiron says, “You can’t do anything but watch it play out.”
Mosquito control is challenging, Paul Baxter says, especially with flooding and bad weather. Photo by Paul and Emma Baxter.
Can You Keep JEV Out?
As of March 29, more than 50 pig farms across the eastern seaboard of Australia and in South Australia were diagnosed with JEV. As of March 31, the Australian Government/Department of Health reported 34 human cases, 24 confirmed and 10 probable across the same geography in Australia.
The worst part of the JEV outbreak in Australia is that the damage was done before anyone even knew it would be an issue, Refalo says. His advice? Remove any water lying around if possible.
“This is impossible to do if you are experiencing a lot of rain – there’s just not a lot that can be done,” Refalo says.
During the webinar, Richards said Australia is addressing the outbreak with a One Health approach, combining human and animal response protocols. Current activities at infected premises include mosquito trapping and control, vaccination of people working at and residing on those premises, and risk-assessed movement of pigs and semen.
“Our industry leaders are saying biosecurity is key to controlling JEV, but I find it hard to see how we can control mosquitoes over such a large area considering it’s affecting the whole of the eastern states,” Baxter says. “We had quite bad weather and flooding which resulted in a perfect environment for mosquitoes to a level we’ve never seen here before. Other than control measures within the sheds, they were uncontrollable around the entire farm.”
Refalo Free Range Pork operates a free-range pig operation in New South Wales. Photo by David Refalo.
What We Wish We Would Have Known Sooner
Knowing the effects on the sows would’ve been advantageous, Baxter says, as it presented on farm a lot like leptospirosis.
“We naturally thought vaccine breakdowns were the cause and spent a lot of money on retreating our herd for things that were later ruled out,” he says.
Refalo and Baxter both admit it’s frustrating because there’s not a lot that can be done but to stay alert and pay close attention to changes in your herd.
“Use your gut instinct,” Baxter says. “When consulting with my vet, I told him what we were dealing with looked different than anything I’d seen before and unfortunately it was.”
More from Farm Journal’s PORK:
Why U.S. Pork Producers Need to Pay Attention to Australia Right Now
Mosquito-Borne Virus Discovered on Australian Pig Farms
SHIC Adds to Preparedness With Updated PTV and JEV Fact Sheets
Japanese Encephalitis Virus Could Happen in U.S. Swine Herds
