A common pig virus at the centre of a looming pork trade dispute is probably already present in Australia and should not be used as a trade barrier, Canadian scientific experts say.
An Australian court ruling that could result in a ban on pork imports from Canada, Denmark and the United States as early as next week is based on politics, not science, said John Ellis, a researcher at the University of Saskatchewan's veterinary college.
"I think is another example of a non-tariff trade barrier, based on very minimal risk to the Australian hog industry," said Ellis, who was an expert witness for the Australian government in the court case.
Australia imported 70,000 tonnes of pork in 2004, mostly from Canada and Denmark.
The country claims it is free of post-weaning multi-systemic wasting syndrome - a disease that causes piglets to stop growing and lose weight at the age of six to 10 weeks.
Australian pork producers won a court case on Friday that could see bans placed on pork imports.
But North American researchers said the virus that causes the disease was likely to be in Australia already because it was present around the globe.
"It's endemic in pretty much every pig population we've looked at," said Ellis, who is part of an international consortium studying the disease.
Porcine circovirus syndrome - the smallest known virus among mammals - causes the wasting disease, and is believed to spread to pigs through the air, via faeces and from sows to their piglets.
Most pigs carry the virus. But scientists are still researching why only a small number develop the wasting disease, which cannot be treated.
There is no evidence the virus can spread to humans who eat meat from infected animals, scientists said.
The virus has existed for decades, but the wasting disease was first detected in the Canadian Prairie province of Saskatchewan in 1991.
Within a few years, scientists realised the disease was widespread in Canada and around the world, said Edward Clark, the University of Saskatchewan pathologist who identified the disease and helped name it.
"It's hard to find a herd that is free of the virus," Clark said. "I don't think there are any, frankly."
Researchers have found other factors that seem to spur the disease, including other health problems, certain ingredients in vaccines, genetics, overcrowding and poor sanitation.
Farmers had reduced the incidence of the disease by limiting those other factors, said Patrick Halbur, an associate dean who specialises in the disease at Iowa State University's veterinary college.
Still, the virus was present in most if not all US herds, and the disease was one of the top five most commonly reported problems for pigs, Halbur said.
He added that a vaccine for the disease should be available in the United States within a year.
If Australia is free of the virus, Canadian scientists said it could be theoretically possible that live hogs could contract the disease by eating imported meat from infected animals, which they noted was not a regular farm practice.
Saskatchewan's Ellis said Australia already had strict feed rules, and forbids imports of pork containing organs and lymph nodes most likely to carry the virus.
"I think it was a long shot, a very big long shot, that importing pork meat from somewhere in the world would be a source of virus entry," Ellis said.
