Some aspects of Senecavirus A continue to mystify researchers

While the spikes of Senecavirus A (SVA) have plateaued in recent years, researchers in the pork industry are still confounded by the elusive virus and what triggers outbreaks.

“We don’t see the large seasonal spikes that we did early on in 2015 and 2016,” Matthew Sturos, DVM, a diagnostic pathologist at the University of Minnesota, told Pig Health Today.

Fortunately, he added, incidence in the years “2017 and 2018 have been fairly static and we don’t really know the reason, but it does seem to be a persistent problem.”

SVA is a small, hardy, non-enveloped virus. Between 1988 and 2015, only a handful of cases were confirmed in the US.

Brazil was the first country to report large SVA outbreaks in 2014 and 2015, Sturos noted. Shortly afterward, several other countries around the world reported large outbreaks, including China, Canada and the US, which reported hundreds of cases. The reasons for the dramatic rise in numbers remain unclear.

Daunting questions

While scientists are learning more about SVA all the time, Sturos said, they have little history to go on.

“We’ve had 30 years to work with porcine reproductive and respiratory syndrome (PRRS), and we’ve had about 3 [years] to work with Seneca Valley Virus, and so there are a lot of unknown questions,” he said.

“How much antibody is antibody protective? How much do you need? And how long after an animal is exposed is it immune? We don’t know those answers. And this does make it difficult to predict.”

Mimics FMD

SVA mimics foot-and-mouth disease, a transboundary illness that can cause heart disease in young animals, he said. He added that there are clinical reports of increased neonatal loss or death in week 1 on farms infected with SVA.

He said many of the findings about the impact of the virus are variable.

“And that’s what makes it difficult,” he said. “The consistent findings in these affected animals [show] they often have diarrhea, they’re infected within the first week of life, and it can be sporadic within the farm. You might have one litter that’s affected, and you have another one right next to it that’s not.”

He said increased biosecurity is the best way to keep the disease away from farms.

“The preventative measures that are in place for the other endemic diseases — PRRS, porcine epidemic diarrhea — those are all important factors,” he said. “Being careful about animals that you bring in; being careful about the equipment, personnel, how you move through your facilities — those are all going to be important in preventing introduction into a herd.”