Dairy cows infected with bird flu in five US states died or were slaughtered by farmers because they failed to recover, state officials and academics told Reuters.
The reports of deaths suggest that an outbreak of avian flu in cows could have a greater economic impact on the agriculture sector than initially thought. Farmers have long culled birds infected with the virus, but raising cows is far more expensive than raising chickens or turkeys.
A spokesman for the US Department of Agriculture (USDA) said the agency was aware of some deaths but most cows were recovering. Reuters was unable to determine the total number of cows that died or have died from bird flu in South Dakota, Michigan, Texas, Ohio and Colorado.
Bird flu has infected dairy cows in more than 80 herds in 10 states since late March, according to the USDA.
Veterinarians, agriculture officials and academics helping with state bird flu responses said some animals died from secondary infections after their immune systems were weakened by bird flu. Other cows were killed by farmers because they were unable to recover from the virus.
According to farmers and veterinarians, cattle infected with bird flu suffer from reduced milk production, digestive problems, fever and loss of appetite.
In South Dakota, a 1,700-cow dairy farm sent a dozen animals to slaughter because they failed to recover from the virus and culled another dozen that suffered from secondary infections, said Russ Daly, a professor at South Dakota State University and a veterinarian with the state Extension office who spoke to the farm.
“If cows get sick with one disease, it causes a domino effect for other things like regular pneumonia and digestive problems,” Daly said.
One farm in Michigan killed about 10% of its 200 infected cows because they also failed to recover from the virus, said Phil Durst of Michigan State University Extension, who spoke to that farm.
Michigan has more confirmed livestock infections than any other state, with two of the three confirmed cases of U.S. dairy workers suffering from bird flu.
In Colorado, some dairy farms have reported killing cows infected with bird flu because they did not return to milking, said Olga Roebuck, a spokeswoman for the state Department of Agriculture.
Infected cows in Ohio and other affected states have died, mainly due to secondary infections, Ohio Department of Agriculture spokeswoman Meghan Harshbarger said.
The Texas Animal Health Commission also confirmed that cows have died from secondary infections at some dairy operations associated with the bird flu outbreak.
Officials were unable to provide data on the number of cow deaths in the states.
