Chicken Waste and Bird Flu in Cows: The Connection?

The recent outbreak of avian influenza, commonly known as bird flu, in the United States has sparked concerns about its potential transmission to dairy cows through the use of contaminated poultry litter. Poultry litter, a mixture of chicken feces, feathers, and bedding materials, is often used as a fertilizer and feed for cattle in some agricultural practices.

The outbreak has affected 34 dairy cow herds across nine states, leading to speculation that the use of poultry litter as cow feed may be a source of transmission. While some states, such as California, have regulations prohibiting the use of poultry litter as feed for lactating dairy cows, it is still allowed for other cattle, including beef cows.

Studies have shown that poultry litter can harbor various bacteria, including salmonella and E. coli. This has raised concerns that the litter may also contain traces of the bird flu virus, which could potentially lead to outbreaks in cattle. However, experts caution that more research is needed to determine the extent of this potential transmission route.

Jodie Guest, the senior vice chair of the Department of Epidemiology at Emory University’s Rollins School of Public Health, emphasized the need for more information on the prevalence of using poultry litter as feed and its association with the bird flu outbreaks. Without this data, it is challenging to establish a direct link between the two.

The Department of Agriculture has stated that wild migratory birds are believed to be the primary source of the outbreaks. However, they have also acknowledged the possibility of other factors, such as infected unpasteurized milk, contributing to cow-to-cow transmission of the virus.

Poultry litter is used as feed for cattle because it is a cheap source of protein and provides a cost-effective way to dispose of chicken waste. The FDA initially discouraged this practice in 1967 but later allowed states to decide. After the first case of bovine spongiform encephalopathy (BSE), or mad cow disease, was reported in the U.S., the FDA temporarily banned feeding cattle poultry litter in 2003. However, this ban was later lifted, and instead, the FDA prohibited the use of cow brains and spinal fluid in chicken feed.

While the European Union and Canada have banned the use of poultry litter as animal feed due to disease concerns, the practice remains legal in the United States.

In addition to the concerns about bird flu in cattle, there have been reports of the virus spreading to domestic cats. This has raised concerns about potential transmission routes, including the possibility of contaminated mink meat being a source of infection. Bird flu was also detected in cat shelters in South Korea in 2023, leading to recalls of certain cat foods.