Avian Flu Waning but Threat Remains

This year’s avian influenza outbreak appears to be waning, following the historical pattern of the disease dissipating in hotter months. However, its exit comes too late to avoid the impact on domestic birds in a variety of settings, including commercial poultry operations, backyard egg operations and hobby farms, gamebird farms, petting zoos, and wildlife rescue and rehabilitation centers. In total, more than 40 million domestic birds in the United States have been “depopulated” to control the spread of highly pathogenic avian influenza (HPAI).

dead birds being hauled away - photo by We Animals
photo by We Animals

As of late June, HPAI had been detected in 376 domestic flocks (186 commercial and 190 backyard) in 36 states. To control spread of the disease, the US Department of Agriculture has established a policy of depopulating all birds in a flock within 24–48 hours of a positive test. The most common methods for killing birds in backyard flocks are cervical dislocation (dislocating the spinal column from the brain) and carbon dioxide gas. 

For commercial poultry operations, the most common depopulation method during the 2022 outbreak has been water-based foam, which kills birds relatively quickly by airway occlusion, and ventilation shutdown plus heat (VSD+), which kills slowly via induced heat stroke. Although USDA policy requires that VSD+ only be used when other, more humane methods are not available or feasible, AWI’s analysis of depopulation data shows that more than half of the 186 commercial depopulations were conducted with VSD+, alone or in combination with another method. At least 8 million domestic birds were killed by arguably the most inhumane method possible. 

Justifications for use of VSD+ during the 2022 outbreak included lack of access to carbon dioxide gas, limitations to the use of foam with caged birds, and difficulties encountered in conducting extremely large depopulations with any method other than VSD+. Approximately 18 percent of the commercial depopulations were conducted at operations of more than 100,000 birds. Even with use of VSD+, depopulations involving such large numbers of birds frequently exceeded 48 hours. According to AWI’s analysis of USDA data, depopulations affecting a total of 22 million birds took more than 48 hours from positive HPAI test to completion of the killing. Four depopulations—all involving over 1 million birds—took 10 days or longer to complete, illustrating the serious threat posed by industrial farming to animal health and welfare. 

The 2022 HPAI outbreak affected wild animals as well, with the USDA confirming 1,635 cases of HPAI in wild birds across the country. Avian influenza circulates freely in wild birds—waterfowl and seabirds in particular—with most wild birds exhibiting no signs of illness (although experts have indicated that the current HPAI strain has proven far deadlier to wild birds than previous strains). Scavenging and migrating birds may carry the virus to agricultural areas, exposing large numbers of domestic poultry. In stark contrast to wild birds, mortality typically exceeds 90 percent in infected domestic poultry. This year’s outbreak may be abating, but the risk remains that it will return with the next bird migration in the fall. Given the inevitability of future outbreaks, the USDA should take steps now to end the widespread use of VSD+ to depopulate domestic flocks.