The spread of bird flu among poultry and dairy farms has raised concerns about the risks associated with the killing and disposal of infected birds, potentially impacting both human health and livestock safety.
Recent data and interviews with experts reveal that improper disposal methods and close contact during the culling process could further exacerbate the spread of the virus. Instances of farms dumping carcasses in landfills and using unsafe killing methods have drawn attention to the risks involved.
Extreme heat on a Colorado egg farm, which affected workers’ ability to use protective equipment during carbon dioxide asphyxiation of chickens, contributed to five bird flu cases among workers—the largest cluster of human cases in the U.S., according to the Centers for Disease Control and Prevention (CDC).
CDC Principal Deputy Director Nirav Shah emphasized the need for strict use of protective gear during the culling process. Dr. Michael Osterholm, an infectious disease expert at the University of Minnesota, highlighted the risks workers face, including inhaling the virus, and stressed the importance of ensuring their protection.
The Colorado Department of Agriculture stated that bird killing methods are chosen collaboratively by the state, farmers, and the U.S. Department of Agriculture (USDA). The virus has now affected nearly every U.S. state over the past 2.5 years, with nine human cases reported among poultry and dairy workers since March.
While the risk to the general public remains low, further bird flu spread among livestock could increase the likelihood of human infections. Since February 2022, approximately 95 million chickens, turkeys, and other poultry have been culled and disposed of, with 2024 seeing near-record disposal rates.
In Colorado, workers used mobile gas chamber carts for culling, which accommodate between 12 and 50 birds per batch. The USDA reviewed these methods as part of its outbreak response. Over 150 workers were exposed to infected poultry, with 69 showing symptoms and five testing positive.
Birds are typically killed by asphyxiation using portable chambers, firefighting foam, or ventilation shutdowns. Other methods include firearms and cervical dislocation.
For disposal, most culled birds are composted on-site or buried. Composting involves covering the birds with materials like wood shavings, maintaining high temperatures, and stirring the compost piles. So far, no direct links have been found between human or livestock infections and the disposal of dead birds.
Disposal methods are coordinated with federal and state officials. Myah Walker, a compliance supervisor at the Minnesota Board of Animal Health, noted that on-site composting is safest to prevent virus spread. However, in rare cases, carcasses are transported to landfills, as seen with Michigan’s Herbruck’s Poultry Ranch, which disposed of nearly two million chickens in landfills. This disposal raised concerns among local farmers, though whole genome sequencing confirmed that the disposed carcasses did not cause the subsequent infection in a nearby dairy farm.
Experts, including Brian Hoefs, the state veterinarian for Minnesota, advise against landfill disposal due to the risk of spreading the virus through scavengers.
