Avian influenza spreads in US, Canada

Highly pathogenic avian influenza has spread to at least 13 commercial poultry flocks since February.

As of March 9, the commercial flocks with confirmed infections together had populations of about 2.7 million birds before the outbreaks, and Department of Agriculture Animal and Plant Health Inspection Service reports indicate those flocks would be depopulated to prevent spread of the disease. More than 1.1 million of those birds were chickens at a single site in Delaware, according to a report from the USDA to the World Organisation for Animal Health (OIE).

Most recently, APHIS officials announced since March 4 that infections had been found among commercial broiler chickens in Missouri, commercial layer chickens in Maryland, commercial turkeys in Iowa, and mixed commercial species in South Dakota.

So far this year, highly pathogenic avian influenza virus has been found in domestic or wild birds in 20 states, mostly in the eastern half of the U.S., according to APHIS reports. That includes H5N1 influenza infections in commercial flocks in Delaware, Indiana, Kentucky, Missouri, Maryland, and South Dakota.

Infections have occurred among backyard flocks of chickens and other birds in Connecticut, Iowa, Maine, Michigan, New York state, and Virginia. By mid-February, surveillance also revealed highly pathogenic H5 influenza virus detections in about 300 wild birds captured alive, killed by hunters, or found dead in 14 states.

Animal health authorities in Canada have also identified H5N1 influenza infections since December among domestic flocks and wild birds in the eastern part of the country. The Canadian Food Inspection Agency announced in February that infections had been confirmed on two farms in Western Nova Scotia, one of them a commercial flock and the other a mixed farm that raised poultry for local sale.

Reports published early in February by the CFIA and OIE describe infections among wild and backyard birds in Newfoundland and Eastern Nova Scotia. One report filed Feb. 3 with the OIE indicates that about 490 birds of various species had been affected. About 380 were killed by infections, and the rest were depopulated, the report states.

AVMA experts note that most avian influenza outbreaks in the U.S. are associated with low pathogenic strains, which may still cause clinical signs of disease in poultry. Highly pathogenic strains, however, can devastate entire poultry flocks and cause illnesses in people and other animal species.