SASKATOON, Saskatchewan (Reuters) - The number of positive or suspicious tests for H1N1 flu in a quarantined herd of pigs in Western Canada has dropped, but food safety officials will test the animals at least once more before considering lifting restrictions.
The Canadian Food Inspection Agency tested the pigs with nasal swabs on May 14 and again last week and found the number of positive or suspicious tests for H1N1 flu had dropped to 13 from 19.
"It's headed in the right direction, but we still haven't had a completely negative herd test," said Dr. Jim Clark, national manager of disease control for the CFIA.
The next round of tests comes on Monday. If the results from the lab later in the week are negative, the CFIA and other government health agencies will consider lifting the quarantine, Clark said.
The CFIA quarantined the 2,200-hog farm in the western province of Alberta on April 28. Some of the animals apparently caught the H1N1 virus from a farm worker who had been to Mexico, where the outbreak began.
The fact that the virus has not been detected anywhere else in the Canadian hog industry suggests either it doesn't generate unusual symptoms or that human contact with swine is limited, Clark said.
None of the farm's pigs has died because of the H1N1 virus, Clark said.
However, the CFIA may consider culling the entire herd if the farmer's patience for testing runs out before the herd is confirmed free of the virus, Clark said.
Hog farmer Arnold Van Ginkel told the Canadian Broadcasting Corp earlier this month that he's frustrated with officials, who he said did not have a clear plan.
"I'm sure there's going to be a point in the future where he's going to lose patience with the process," Clark said. "That's when I think we talk about alternate approaches. We can't maintain this herd where it is forever. Decisions will be made based on his willingness to continue."
Any decision to slaughter the herd will also consider other health agencies' opinions and the view of Canada's export pork markets, he said.
The CFIA maintains the position that if the herd tests negative for the virus, the pork would be safe to enter the human food supply. However, some industry officials and Van Ginkel himself have said it may be wiser to cull the herd as the animals are unlikely to find buyers.
The herd is now as large as 2,500 pigs because of reproduction, and will require a second cull soon to deal with overcrowding, Clark said. Three weeks ago, the CFIA culled 500 animals for that reason.
Carcasses from the culled pigs did not enter the human or animal food supply, Clark said.
Thirteen countries have placed bans on pork, swine or both, from Canada or some of its provinces, since the outbreak of H1N1 flu began.
Editing by Rob Wilson