The transmission of the new H1N1 virus from a man to a herd of swine in Canada is a reason for concern and confirms the need for increased surveillance of pig farms, the United Nations food agency said on Sunday.
However, Joseph Domenech, chief veterinary officer at the Food and Agriculture Organisation, said the incident was not surprising and reiterated pork and pork products handled in accordance with good hygienic practices were safe to eat.
"We are concerned that this happened but we are not panicking," Domenech told Reuters. "It just reinforces the principle that surveillance of pigs must be intensified."
Canadian health officials said on Saturday a swine herd in the western province of Alberta had apparently caught the virus from a carpenter who recently travelled to Mexico, the epicentre of a swine flu outbreak that has spread to 19 countries and may have killed more than 100 people, all but one in Mexico.
It was the first time the Canadian Food Inspection Agency had reported a case of the virus being transmitted from a human to a pig in Canada.
"It's rare but we have said from the beginning of this flu outbreak that this might happen," Domenech said.
He said FAO was awaiting the results of tests conducted in at least two laboratories in the United States and Canada, where strains of the virus isolated in humans in Mexico had been inoculated into pigs.
The Canadian Food Inspection Agency said the infected herd was quarantined pending more testing and the chance the pigs could transfer the virus to humans was remote. It said all the infected pigs had recovered or were recovering.
"That means it could be one of the viruses variously circulating in pigs that are not too severe, that can be dealt with in a normal way by strengthening surveillance and biosecurity of the pig population," Domenech said.
Doctor Alex Thiermann, advisor to the director general of the World Organisation for Animal Health, also said surveillance was key.
"One has to monitors the health of all pigs ... Animals that are showing signs of illness cannot be marketed and cannot be slaughtered. After this event there is no need to make any changes in the recommendations," Thiermann said.
"Pigs are occasionally known to have influenza and they fully recover and are no longer infectious. In the pigs, once they recover, you can detect antibodies ... that the virus is no longer there," he added.