Discovery of Brucella suis in wild pigs means farmers, hunters and commercial pork producers need to keep their guards up.
By Rose Hoban
Go for a walk in the woods of North Carolina and you might expect to encounter deer, rabbits, squirrels or birds; the idea of running across a wild pig isn’t uppermost in the mind of most people here.
But North Carolina has a sizable population of feral pigs, and researchers have evidence that a bacteria dangerous to both pigs and people is now in the state.
According to new research from North Carolina State University, some feral pigs have been exposed to Brucella suis, a bacteria that should have hunters, farmers and people in the commercial pork industry keeping close watch.
“It’s an old disease but we don’t see it often in this country, so its easy to overlook,” said Suzanne Kennedy-Stoskopf, professor of wildlife infectious disease at NC State and one of the authors of the paper, published in the Journal of Wildlife Diseases. “Some physicians would see it and not recognize it.”
B. suis can cause pregnant pigs to spontaneously abort their fetuses, and can do the same to humans. But more often, B. suis causes fever, fatigue and body aches, similar to a bad case of flu.
“If it’s not diagnosed you will feel awful for a long time because it causes chronic illness that lasts for years, with some pretty debilitating arthritis,” said Kennedy-Stoskopf. In rare cases, an untreated case of B. suis can cause swelling of the brain.
An infection, if identified, is treatable by a course of antibiotics.
Kennedy-Stoskopf said the biggest risk is to hunters, who might bag a feral pig in the woods and be exposed to the bacteria during the course of cleaning and dressing the animal. B. suis is carried in the blood and other bodily fluids of infected pigs. The bacteria is destroyed during cooking.
She said hunters can protect themselves, but worried that doesn’t happen often enough.
“We provide gloves, dustmasks, eye protection for the hunters here,” said Mike Rose, a manager at Howell Woods, an environmental education center in southeastern Johnston County where the NC State researchers found nine pigs that tested positive to antibodies against B. suis.
Rose said Howell Woods provides an area for cleaning animals shot on the preserve, and the area has signs posted warning hunters of the risks of trichanosis, salmonella and other pathogens. But he said most of the hunters don’t wear the protective gear.
“They just wear the gloves. And if we didn’t make them wear the gloves most probably wouldn’t do that either,” Rose said.
Old invaders
Pigs are not native to North America. There’s still some debate among historians as to which European explorer brought the first swine to the New World, but they do agree it was within a decade of Columbus’ arrival.
Once they arrived, pigs spread across the continent easily. There was plenty of food, no natural predators, and the pigs adapted and reproduced quickly. Wildlife biologists estimate as many as 5 million feral pigs roam more than 37 states of the U.S. Most feral pigs in North Carolina can be found in the Smokies, but there’s also a sizable number in eastern and southeastern counties.
Many pigs in nearby states such as South Carolina and Florida carry Brucella bacteria. They could have migrated here, or they could have had help, according to the researchers who wrote the paper.
“Hunters will go out of the state, they’ll hunt the feral pigs, catch them in traps and haul them up here,” said Chris DePerno, associate professor in the Fisheries, Wildlife and Conservation Biology program at NC State and a co-author of the paper.
When asked why, DePerno replied, “They’re good eating and fun to hunt. They’re they’re challenging, and they’re smart.”
But as of the beginning of this year, transporting feral pigs into North Carolina could cost you. Legislation passed in the General Assembly last year went into effect on Jan 1 making it illegal to bring wild pigs here from other states, and adding new fines of up to $5000 per pig carried to North Carolina.
Because feral pigs carry diseases like Brucella.
Commercial swine farmers wary of B. suis
“Pigs can transmit more than 30 diseases,” said Barbara Schellinger, a biologist at the North Carolina office of the USDA in Raleigh.
“It would be economically devastating to the pork industry if any of of these (diseases) crossed into the commercial population,” Shellinger said. That’s why both the US and NC Departments of Agriculture collect blood samples from pigs caught by hunters all over the state, looking for a variety of pathogens, including Brucella.
North Carolina has the second largest commercial production of pigs in the US, with an estimated value of $792 million in 2010.
DePerno, Kennedy-Stoskopf and their collaborators collected blood samples from more than 400 pigs killed by hunters or caught in baited traps over the course of three hunting seasons. They detected a total of ten pigs that had antibodies to B. suis, indicating that the pigs either were infected or had been infected.
Kennedy-Stoskopf said most commercial pig farms practice measures intended to keep bacteria and viruses from getting to their animals, but she said there’s still a slight chance a disease from a wild pig could get into a commercial operation.
“The demand for free range pigs is growing,” Kennedy-Stoskopf said. “And even with fencing, you can’t keep feral swine out of your farm. They’re going to co-mingle. So, we don’t know what’s the risk of introducing Brucella into these pasture-reared pigs.”
“We can make guesses, but we don’t know,” she said. “It will require heightened surveillance on the part of producers. and not just assume that it was eliminated from industry, assume that they’ll stay Brucella free.”
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