The number of U.S. turkey flocks to be affected by highly pathogenic avian influenza (HPAI) in 2022 is about four times the number layer and broiler flocks combined.

 So why are more flocks of U.S. turkeys experiencing H5N1 infections than flocks of chickens?

Dr. David E. Swayne, laboratory director of the U.S. Department of Agriculture’s in-house high biocontainment laboratory for poultry health research, offered one possible explanation on the matter during the webinar, Facts About Highly Pathogenic Avian Influenza Spread and Control, hosted by WATTPoultry.com and sponsored by Boehringer Ingelheim on May 26.

Studies have been conducted at multiple laboratories, including the one that Swayne leads, and experimental data from those studies indicate that turkeys are more susceptible to low pathogenic avian influenza viruses and produce infections that can be spread from turkey to turkey, said Swayne.

But, more specifically, when studying the virus of the goose/Guandgdong lineage that is presently being seen, scientists have observed that the virus is more transmissible from turkey to turkey than it is for chicken to chicken, Swayne said. He also pointed out that it generally takes a lower inoculation dose to infect turkeys than chickens, which he said could be why more premises operated by turkey producers have been infected than premises with chickens.

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As of the day the webinar was held, HPAI had been confirmed in 120 commercial turkey flocks, 10 flocks involving turkey breeding stock and 1 involving poults, whereas the virus has been confirmed in only 11 broiler flocks and 20 layer flocks, with nearly proportionate numbers of breeding stock and pullet flocks affected.

In Canada, HPAI has been confirmed in commercial turkey, layer and broiler flocks. However, information concerning the type of poultry affected in certain affected flocks has not yet been released, making it difficult to determine whether more turkey flocks have been affected than chicken flocks.

An archived version of the webinar can be accessed on WATTPoultry.com. Register to attend the webinar.

To learn more about HPAI cases in North American commercial poultry flocks, see an interactive map on WATTPoultry.com.

Read our ongoing coverage of the global avian influenza outbreak.