For years it has been absent from western Canadian hog barns, but now swine dysentery is back in Canadian and American herds.
“From my understanding it was in the mid-1990s when classical swine dysentery, brachyspira hydosenteriae, sort of went off the radar,” Joe Rubin told the 2012 Canadian Swine Health Forum in Winnipeg last week.
The post-doctoral fellow at the University of Saskatchewan has been working on developing methods of positively identifying the bacteria in swine, as well as looking at what appears to be a new species of the bacteria under the same genus.
In its classic form, the bacteria can cause prolonged and sometimes hemorrhagic diarrhea in animals.
What the new species will be called and how it will be identified is still being worked out.
“We haven’t quite got our nomenclature down yet,” said Rubin, but the term brachyspira 30446 is being used in the interim.
The new strain of the pathogen doesn’t appear to cause symptoms as severe as brachyspira hydosenteriae, but both the old and new strains have emerged in hog barns.
In 2003 cases of swine dysentery reappeared in American hog barns, while the first cases in Western Canada appeared in 2009. In 2010 four cases were reported in Quebec.
“We have a clearly emerging problem in North America,” Dr. Doug MacDougald of South West Ontario Veterinary Service told attendees.
He added that communication between producers, industry and researchers is crucial to addressing the disease as it emerges.
“I think that we are in the same stage in the U.S. as in Canada, we’re trying to keep it controlled and come up with a good method of detection,” said Eric Burrough of Iowa State University, who spoke about the American experience with the disease.
But Rubin points out a lot of basic biology still needs to be done on this new species of brachyspira affecting herds.
“Where did it come from? We don’t really know a lot about where these organisms hang out when they’re not in pigs,” he said.
Suggestions have been made that rodents or wild birds are responsible for the re-emergence, but so far no studies have been conclusive.
Rubin notes studies looking at birds living on hog farms have found them to contain the bacteria, but the question then becomes a chicken or egg discussion.
“Did the birds bring it with them to the farm? Or did they pick it up while living near the hog barn? We just don’t know,” he said.
Other preliminary discussions have led to the suggest contaminated surface water may be playing a role in the spread, but no formal research studies have tested that hypothesis.
Janet Hill of the University of Saskatchewan is leading that school’s brachyspira research program and said they will soon begin inoculation trials with brachyspira 30446.
“It’s a really important step when studying potential pathogens,” she said. “Just because you can isolate and detect an organism in association with disease, doesn’t necessarily mean the organism is the cause.”
Once causation is firmly established, the next step is to look at the epidemiology of the disease and determine its origin.
“I think a lot of people were surprised to see this,” she said. “With improved biosecurity it was not expected.”