Songbirds, rodents not likely vectors in avian influenza outbreak

Songbirds and rodents are unlikely to have transmitted highly pathogenic avian influenza onto farms in 2014 and 2015, according to findings in a recent study.

The study, "Evaluating the role of wild songbirds or rodents in spreading avian influenza virus across an agricultural landscape," was published in December 2017 in PeerJ (https://peerj.com), an open-access biological, medical, and environmental sciences journal. Researchers affiliated with Iowa State University, Western State Colorado University, and the Department of Agriculture's Animal and Plant Health Inspection Service conducted the research.

Highly pathogenic H5 avian influenza viruses killed or led to depopulation of about 50 million domesticated birds, more than 40 million of them chickens.

Migratory waterfowl and shorebirds are avian influenza virus reservoirs, but they are rare on poultry farms. Transmission to domestic birds likely occurs through other means, and human activities are thought to be among those means, the authors wrote.

The avian influenza outbreak in 2015 spread to poultry farms with strict biosecurity, and the authors suspected local wildlife could have transferred the avian influenza virus from waterfowl and shorebirds to the farms.

The researchers captured and swabbed about 300 small birds and 150 rodents in wetlands near poultry facilities during fall 2015 and spring 2016. None of the samples were positive for presence of influenza A virus, and serology from about 400 of them showed no antibodies against influenza A. The researchers also collected samples from more than 500 waterfowl, and 16 percent were positive for influenza A virus.

The results indicate small birds and rodents were unlikely bridge hosts between reservoirs and farmed birds, the article states.  

Related JAVMA content:

Devastating flu, ongoing harm (Sept. 1, 2015)

Devastating viruses disappeared in wild birds (Sept. 15, 2016)