Allowing hogs to root around outdoors could lead to a resurgence of historically significant parasites, says an American researcher.
Hogs confined in close quarters are more susceptible to infectious disease and need to be treated with antibiotics, but that practice has been blamed for causing the proliferation of antibiotic-resistant bacteria.
However, Wondwossen Gebreyes of Ohio State University said it may be misguided to think the problem can be solved by getting pigs off drugs and letting them root around in the sunlight and fresh air to build up natural immunity to bacteria.
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“In recent decades, we have moved from raising pigs outdoors to indoors. All that really protects us from is parasites, and problems relating to parasites, including trichinella,” he said.
“Now that we are reusing these outdoor, animal-friendly production systems, that could be conducive to a resurgence of several kinds of parasites.”
Concerns over antibiotic resistance have put pressure on governments to force the livestock industry to stop using certain medications, but Gebreyes said there may be no easy solution.
“If you don’t give antibiotics and you want to raise pigs in confinement, then (mortality) is a problem. But if you don’t want to give antibiotics and you raise them outside, then maybe you’ll have very serious problems with parasites.”
In a study that took 675 serum samples from hogs in Wisconsin, North Carolina and Ohio, researchers found that salmonella, toxoplasma and trichinella antibodies were more likely to be present in animals raised under the free-range, antibiotic-free model than in a conventional confined environment.
Salmonella was found in 54 percent of the outdoor and 39 percent of the indoor hogs.
Toxoplasma, a parasite commonly harbored by house cats that can cause birth defects such as hydrocephaly in fetuses, was found in seven percent of outdoor hogs and one percent in conventionally raised animals.
Two of the hogs, both from the antibiotic free group, tested positive for trichinella, a parasite that has been nearly eradicated in livestock but is still present in rats and wildlife such as bears.
Gebreyes said the meat from those animals wasn’t inspected for the presence of trichinella cysts, but the presence of high levels of antibodies is a strong indication of persistent infection that could be passed on to humans if the meat was not properly cooked.
The presence of two positive cases in a sample of more than 600 animals is cause for concern, he added, because in 2000 a U.S. Department of Agriculture survey of 14,000 conventionally raised hogs found only one case.
“It’s significant because we found it just in the outdoor pigs,” Gebreyes said. “The question is, if we do more ABF (antibiotic free) pigs outdoors, we could be at risk for a re-emergence of this almost eradicated pathogen.”
According to a fact sheet from the U.S. Centre for Disease Control, cooking meat at higher than 77 C is the only sure way to eliminate the risk of trichinellosis. Smoking or curing meat may not kill infectious cysts in meat, it added.
“All of these problems could be solved by thorough and proper cooking,” Gebreyes said.
Trichinellosis was once common in humans, the fact sheet added, but incidence of the debilitating and often fatal disease has been reduced to an average of 12 cases per year in the United States.
