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The big imposter: Senecavirus A prompts frequent false alarms at Minnesota pork plant

12 July 2018

Poultry Health Today

Employees at the Hormel pork-processing plant in Austin, Minn., well understand the drill for a foreign animal disease (FAD) investigation.

The plant experienced 90 FAD investigations for foot-and-mouth disease (FMD) over the past several years, according to A.J. Shute, hog-procurement manager.

In all cases, results were negative for FMD. Instead, the culprit was an FMD imposter — Senecavirus A (SVA), also known as Seneca Valley Virus. Because its symptoms mimic FMD, SVA triggered the FAD alarms at the packing plant.

Symptoms for SVA and FMD include blisters or lesions on the nose, as well as hoof-pad or interdigital lesions. If pigs come into the plant with these FMD-like symptoms, they must be reported to state or federal animal disease control officials even if SVA is the suspected virus.

False alarms increase

“In 2015, we started seeing more cases of SVA,” reported Fabio Vannucchi, DVM, assistant professor, University of Minnesota (UM). “The big issue is it is a false alarm. It mimics FMD clinically and is very scary for the industry and public.

“The FMD diagnostics take up the time of laboratories, veterinarians and state officials. It is a huge inconvenience when you think about packing plants that must stop (pig movement) for FMD,” Vannucchi told Pig Health Today.

The inconvenience and cost due to FAD investigations adds up for processors like Hormel.

“We must minimise movement and segregate pigs, which is difficult because we have 120 semi loads of hogs arriving every day and 100 employees working in the livestock area,” Shute explained.

Prepared for FAD

The first FAD investigation at the plant occurred in 2007. “We had a scare with a load of pigs imported for slaughter from Canada,” Shute recalled. “It was a close call and we really learned what it takes for communications between different government bodies and how Hormel should be better prepared as well as our producers.”

Today, the Hormel plant staff knows what to do if an FAD investigation is triggered at the plant.

“We avoid all unnecessary cross-traffic of employees from the plant processing areas to the livestock lairage area until an FAD diagnostician arrives and gives further instructions,” Shute said.

The plant staff also begins collecting information that will be needed by the FAD diagnostician. Doing as much as possible right away will help complete the investigation quickly.

“We collect information at the source farm that will be needed when looking at the spread of the disease,” Shute said. “Because we require premise IDs, we know the farm and barn these pigs came from but are there last-minute changes? Who is the point person for the organization?”

The FAD diagnostician is dispatched from the state animal board of health to test with oral swabs of fluid from vesicles. Shute makes sure they are ready to help obtain samples so there’s a quick turnaround in testing. “You won’t be able to move those pigs until there are negative test results,” he explained.

Testing for SVA has improved with same-day PCR (polymerase chain reaction) testing of oral swabs.

Reducing false alarms

In an effort to reduce the number of FAD investigations, Hormel trains its livestock crew to be on the lookout for FADs. The company also has sent letters to all its producers informing them about the SVA and FAD investigations. Shute said they also have shared many photos of suspect pigs with caretakers at farm sites.

But more education about SVA is needed on the farm. “The farm staff is not especially equipped to see it,” Shute said. “On most of the farms with cases, this is not their first load of hogs out of the building. Most buildings are over half marketed and some are down to the last load. So we have some biosecurity breaches happening, maybe on transportation or farm staff across production sites.”

The virus is very stable and will survive in most environments, including trailers, according to UM’s Vannucchi. He and other researchers are trying to learn more about the virus to mitigate the disease.

One early suggestion is using hydrogen peroxide to kill the virus in trailers. “Hydrogen peroxide has been pretty effective against SVA,” Vannucchi noted.

Unprepared for real FAD

“In the case of some widespread FAD outbreak, we are way outgunned,” Shute stated. “We do not have enough experts, testing facilities, etc., to do something that is widespread.

“In fall 2016, we had 10 to 20 cases of SVA a week at the Austin plant, and Iowa had a few cases. The state of Iowa was overwhelmed and could not make it to the farms to close the loops on these disease investigations.

“So, in an actual emergency, how would we be able to deal with that as a veterinary community and industry?” he asked.



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