Wild birds are seen as the carriers of a "low-path" H5N2 avian flu virus that hit a turkey farm in Abbotsford, B.C. in January.
But how a second nearby farm got infected is still unknown, the Canadian Food Inspection Agency said Thursday.
In its report on its investigation of a low-pathogenicity ("low-path") H5N2 avian flu outbreak on two poultry farms in B.C.'s Fraser Valley, CFIA said the disease on the first farm is "believed to have resulted from contact with wild birds."
That, in turn, emphasizes "the importance of biosecurity in preventing the introduction of avian influenza viruses into commercial poultry operations," CFIA said.
Avian flu was originally detected on the first farm on Jan. 21, CFIA said in its report. The same flu virus then appeared on another nearby farm Feb. 10.
All birds on both farms were gassed and composted on-site. In all, 45 area farms that were near the infected properties, or that were connected by shared equipment or other contact, saw movement restrictions imposed on their birds or bird products after avian flu was found on the two farms.
Once the flu outbreak was quarantined, contained and eliminated, CFIA conducted "targeted, enhanced surveillance" for three months and no new cases were detected.
The report, written by CFIA epidemiologist Dr. Krista Howden, noted the virus sequence identified in the Fraser Valley outbreak was "most closely related to an H5 virus identified from a wild bird in California in 2007."
However, Howden wrote, there's nothing to link the second farm to the first in terms of disease epidemiology. On the second farm, the source of the flu virus "was not determined."
Restrictions placed on the movement of birds onto the first infected premises were released on March 17 and for the second on April 1, 21 days following the completion and CFIA approval of cleaning and disinfection.
Canada is currently considered disease-free for notifiable avian influenza and, as per World Organization for Animal Health (OIE) standards, retains its status as free of highly pathogenic ("high-path") bird flu.
Canada regained the latter designation in April 2008 after cleanup of an outbreak of high-path H7N3 avian flu on a poultry farm near Regina Beach, Sask.