Highly Pathogenic Avian Influenza in British Columbia - Outbreak Overview

Disease Detection

Avian Influenza (H7) of low pathogenicity was first detected on February 19, 2004 in birds from a commercial chicken breeder farm in British Columbia's Fraser Valley. The farm was immediately quarantined and all birds were depopulated.  Highly pathogenic avian influenza (HPAI) was detected on the same farm on March 8, 2004.  Surveillance activities detected HPAI virus on a second commercial operation, approximately three kilometres from the first, on March 11, 2004.

Disease Spread

By mid-May, birds on 42 commercial and 11 backyard premises had been declared infected with highly pathogenic avian influenza. Most of these premises were concentrated in one of three clusters of infection. The Canadian Food Inspection Agency conducted investigations on all infected premises, tracing any movement that may have spread the virus.

While there is no definitive epidemiological evidence indicating that wild waterfowl were the original source of the outbreak, scientific literature recognizes these birds as natural reservoirs of avian influenza virus. The farm-to-farm movement of people, equipment or birds likely spread the virus over long distances, but once the virus was introduced into a densely populated region, airborne transmission through dust or feathers may have infected nearby flocks. 

Response

To contain disease spread, the Government of Canada established movement restrictions and disinfection checkpoints, and took legal steps to require bird owners to prevent unauthorized access to their property. As well, the Government initiated a targeted depopulation program that focused on rapidly isolating, containing and eliminating detected cases of avian influenza. Susceptible birds present within three kilometres of infected premises were also depopulated, given the contagious nature of the virus.

All infected birds were humanely destroyed, primarily using carbon dioxide gas. Disposal methods included incineration, burial or composting. Birds targeted for depopulation that tested negative for highly pathogenic avian influenza were eligible for slaughter through normal commercial channels.

By June 3, surveillance of flocks in the Fraser Valley had not detected any new cases of infection for 21 days. Depopulation activities were officially suspended on June 4.

Recovery

The Agency required all premises on which highly pathogenic avian influenza had been detected to be thoroughly cleaned and disinfected. With ongoing surveillance and precautionary movement restrictions in place, premises outside of the municipal boundaries of the City of Abbotsford were permitted to begin restocking on June 10. Premises within the City's municipal boundaries, where the majority of infection was detected, became eligible to restock on July 9. This date marked 21 days since the last infected premises had been satisfactorily cleaned and disinfected.