WASHINGTON, Dec. 9, 2015 - For generations, farmers have observed newborn and other young pigs beset with tremors sometimes so severe that the pigs can’t suckle and they starve to death. Often called “the shakes,” it has been a nervous system disorder with no specific name and no cure, and otherwise healthy piglets most often survived it.
Now researchers at Kansas State and Iowa State universities, using next-generation sequencing, which quickly reads millions of samples of genetic material, have identified the culprit virus and can tell farmers why their little pigs shiver. At KSU’s Veterinary Diagnostic Laboratory, researcher Benjamin Hause calls the newly discovered pathogen atypical porcine pestivirus, or APPV.
Pestivirus strains have long been linked to cow and sheep diseases and classical swine fever in pigs. Hause reports his team had earlier discovered the new pestivirus but didn’t link it to pigs until it got blood samples from two North Carolina farms where 700 weaner pigs (age five to 14 weeks) had gotten the shakes so severely last spring that they died.
The KSU lab also tested pig blood samples from around the Midwest earlier this year and discovered antibodies to the newly found pestivirus in 90 percent of samples. That means most pigs have had the APPV pathogen in their lives, whether showing symptoms or not, Hause explains. However, it seems often to cause tremors in pigs at birth and/or during the first months of life.
Hause says he hopes that KSU’s tests to detect the virus will lay groundwork to understanding it better in time. The heavy losses to tremors in North Carolina are apparently very unusual in the U.S., he says, but the potential for spreading quickly to other farms and causing big problems across a region is unknown. “I hesitate to say anything, because we lack information. In terms of how easily it spreads: we have no idea,” he says.
At the ISU Veterinary Diagnostic Laboratory, veterinarian Bailey Arruda agrees: “The epidemiological data on this one is scarce.” Her team identified a nearly identical pestivirus earlier this fall in blood samples from Iowa, Illinois and Missouri, causing the same symptoms, except they were congenital, surfacing in newborns rather than in weaner pigs. Also, the shaking didn’t usually kill the baby pigs. Like Hause, she says, “Unfortunately, we do not know how it is transmitted.” USDA’s Animal and Plant Health Inspection Service and the National Pork Board told Agri-Pulse that neither has information on APPV, and deferred to KSU and ISU scientists.
Hause and Arruda say farmers who see serious incidence of tremors in pigs can send blood samples to their university labs to identify APPV. Arruda says at least one drugmaker plans to develop a vaccination against this pestivirus strain. Meanwhile, for affected young pigs, she recommends, “supportive care – make sure they get colostrum and adequate milk intake” to avoid dehydration. “Just good husbandry is your best bet,” she says.
In another swine health development, KSU and University of Missouri researchers announced this week that they have bred pigs that resist the porcine reproductive and respiratory syndrome, or PRRS, a scourge in U.S. herds for nearly 30 years.
The scientists, together with Genus plc, a biotech company, succeeded in developing pigs missing a specific gene, called “CD 163,” that the PRRS virus needs to thrive in swine. Thus the virus, which slows swine growth and inhibits reproduction, is itself blocked. "At the very least, the development of PRRS-resistant pigs is a new tool for improving pig well-being and reducing economic losses," said Raymond "Bob" Rowland, KSU professor of diagnostic medicine and pathobiology.
Bob Stallman, president of the American Farm Bureau Federation, called the development “a critical breakthrough” in hog farmers’ battle against the disease, which he said causes an estimated $664 million a year in lost productivity.
“Being able to fight this disease through advanced genetic technologies will mean healthier animals, more efficient food production and more efficient risk management options for producers,” he said.
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