Dairy cows in Michigan have been diagnosed with highly pathogenic avian influenza, the Michigan Department of Agriculture and Rural Development announced on March 29.
The news comes four days after the U.S. Department of Agriculture announced that the virus was found in dairy herds in Texas and Kansas.
The Michigan dairy cows, located in Montcalm County, had recently moved from an affected herd in Texas before any animals were symptomatic.
The strain found in Michigan is similar to the strain confirmed in Texas and Kansas that appears to have been introduced by wild birds. However, this new case upended the belief that mammals were a dead-end host for the bird flu.
“Spread of symptoms among the Michigan herd also indicates that HPAI transmission between cattle cannot be ruled out,” the USDA said in a March 29 statement.
Farmers across the country are urged to practice good biosecurity, test animals before necessary movements, minimize animal movements and isolate sick animals from the herd, as well as limit contact between cattle and wild birds.
There is still no risk to the commercial milk supply as federal regulation requires milk from sick animals to be diverted or destroyed. Additionally, pasteurization has proven to inactivate bacteria and viruses, like influenza, in milk.
Raw milk
There is concern, though, for producers who sell raw milk or use raw milk to make cheese. The virus has been detected in unpasteurized milk samples from sick animals, the USDA said.
It is not illegal to consume raw milk, but the FDA bans it from being sold or distributed across state lines. The FDA has a longstanding position that consuming unpasteurized milk can pose serious health risks to consumers. Each state has its own regulations surrounding the sale of raw milk, with 30 states allowing it in some form.
Spread
The disease seems to affect mostly older dairy cows in mid-lactation. Symptoms include thick and discolored milk along with a sharp reduction in milk production, as well as decreased appetite and a fever. Most cows recover with supportive care.
More than 82 million domestic birds have been culled as a result of the current bird flu outbreak, which started in February 2022. The bird flu has been detected in more than 200 mammals, mostly wild animals. Bird flu detections tend to be higher in the fall and spring as wild birds, primarily waterfowl, that naturally carry the virus migrate and spread it in their droppings.
The first domesticated ruminant to be diagnosed with HPAI was a goat kid in Minnesota last month. The goats lived on a property where a backyard poultry flock had recently been hit by HPAI. The birds and goats had access to the same space and a shared water source. Several goat kids died, but adult goats tested negative for the virus and appeared healthy.
