Wild bird influenza survey, Canada, 2005

Area of Science:

• Veterinary Virology
• Wildlife Epidemiology
• Avian Influenza Research

Background:

• Wild waterfowl are natural reservoirs for influenza A viruses (IAVs).
• Understanding IAV prevalence in wild bird populations is crucial for disease surveillance and control.
• Canada's diverse waterfowl populations present a significant ecological niche for IAV circulation.

Purpose of the Study:

• To determine the prevalence of influenza A virus (IAV) in wild ducks sampled in Canada.
• To identify specific IAV subtypes, including H5, and their distribution within the sampled population.
• To assess the role of mallards and age demographics in IAV transmission.

Main Methods:

• Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used for viral detection.
• Influenza A matrix protein (M1) gene and H5 gene sequences were targeted.
• Sampled ducks were categorized by species (primarily mallards) and hatch year (2005).

Main Results:

• Influenza A virus (M1 gene) was detected in 37% of 4,268 wild ducks.
• The H5 gene sequence was identified in 5% of the sampled ducks.
• Mallards comprised 61% of samples and were disproportionately represented among positive cases (73% for M1, 90% for H5).
• Ducks hatched in 2005 constituted 80% of the total sample, indicating a potentially higher infection rate in younger birds.

Conclusions:

• Wild ducks in Canada harbored significant levels of influenza A virus in 2005.
• Mallards played a key role in the circulation of both general influenza A and H5 subtypes.
• The high proportion of 2005-hatched ducks suggests recent viral introduction or increased susceptibility in young birds.