GUELPH, Ont. A Canadian professor calls his research team?s recent discovery of a link between bacteria known as MRSA and hogs in North America a red flag to health-care institutions.
Scott Weese, a veterinarian in the Ontario Veterinary College at the University of Guelph, Ont., who specializes in antibiotic resistant bugs that pass back and forth between humans and animals, said the November 2007 finding is important because it shows the methicillin-resistant Staphylococcus aureus (MRSA) bacteria can be readily passed from animals to humans even when contact between the two are limited.
Until recently, conventional wisdom had MRSA pegged as an infection occurring mainly in hospitals. A Journal of American Medical Association study found that even healthy people are developing MRSA infections.
Weese?s research now backs up earlier Dutch and British studies that show similar links between hogs and humans.
?Questions remain unanswered, but the finding should be a red flag to health-care institutions,? Weese said. ?Although MRSA doesn?t typically cause illness in pigs as it does in people, pigs could perhaps send this back into the human population.?
Weese acknowledged that while no studies about MRSA in hogs have yet been done in the United States, he said he would be utterly amazed if the bacteria is not present in this country.
?If the same strain is in pigs in Europe, Asia and Canada, I don?t see how it can not be in the United States,? Weese said. ?MRSA does not cause overt disease in pigs so you don?t know until you culture pigs or start seeing MRSA infections in people that are in contact with pigs. I suspect that we are lagging behind Europe and that we will start to see pig-associated MRSA infections in pig farmers and vets.?
In 2006, Weese and others at the University of Guelph found MRSA in domestic animals such as dogs, cats and horses. It was determined at that time the bacteria could be transmitted from animals to humans and vice versa. But human-animal contact tends to be different in those species than it is in pigs, he said.
Weese, along with professors Cate Dewey and Robert Friendship and graduate student Taruna Khanna, found no difference in the prevalence of MRSA among suckling, weaning and grower-finished pigs, but they concluded that people working on hog farms are at higher risk for MRSA than the general population.
The researchers sampled 285 pigs on 20 hog farms in Ontario and found two main strains of MRSA. One strain, the European strain, had previously been found in hogs in Europe and has emerged as an important cause of disease in people in some European countries including The Netherlands and England.
The other strain, called USA 100, is the most common MRSA strain found in people in Canada, according to a news release issued by the University of Guelph.
Of those 20 farms, nine, or 45 percent, were identified as having MRSA in some capacity. That included one in four hogs and one in five farmers on those nine farms. It?s important to point out that research was done on typical Ontario farms and not CAFOs. Weese said individual hogs or small groups of hogs represents a more true representation of the bacteria spreading, implying the transmission could be much greater in a CAFO.
Weese suggested that rate of MRSA is much higher than in the general population.
?The presence of MRSA in pig farmers was quite high ? 20 percent ? compared with the general population in North America, which has a colonization rate of 1 to 2 percent,? Weese said. ?The reason for this is unclear, but further research is necessary to identify and implement control measures to reduce the impact of this pathogen.?
Weese recently told the Canadian TV network CTV, there is concern in Canada that MRSA passed from hogs to humans could escalate as it did in the Netherlands in the past five years.
?The concern is there?s this reservoir in pigs that?s being spread into people that work with pigs and now it?s being spread into the general population,? Weese told CTV.
MRSA is a version of the bacterium carried on the skin and in the nose that can cause skin, soft tissue and other infections. Occasionally, ?staph? ? as it is commonly referred to ? can get into the body and in rare cases cause an infection such as pneumonia in both humans and animals.
MRSA is resistant to many common antibiotics, which can make treatment more difficult. In most cases, MRSA causes very minor symptoms or none at all, but in rare cases, it can lead to death, even in otherwise healthy people.
The professor said it?s too early to say whether there is a way to prevent or reduce MRSA in hogs. He said there are presumably some measures that can be taken, but lack of knowledge and evidence has science currently at bay. He didn?t say what those theoretic measures might be.
?Because pigs are food-producing animals, the finding could raise concerns about food contamination,? Weese said. ?But the food-borne risks are probably minimal. The greater concern is the potential for pigs to serve as a source of MRSA infection for people in contact with the animals. It?s also important that people, especially pig farmers but probably also cattle farmers, realize that they are likely now or in the near future at higher risk for MRSA infection, as is the case in some areas of Europe.?Minnot Daily News
