The United States Department of Agriculture (USDA) updated stakeholders last week on how a Highly Pathogenic Avian Influenza (HPAI) strain may have spread to dairy cattle in several states.
In an April 4 international online meeting, reported by science.org, department officials said the virus—which started its multi-state spread sometime in late March—may be “expanding its reach” through milking equipment, dairy workers managing infected milk or both.
This means the virus may not be spreading via cows’ respiratory systems as previously submitted.
“We haven’t seen any true indication that the cows are actively shedding virus and exposing it directly to other animals,” said USDA’s Mark Lyons, as quoted by science.org. Department scientists also suggested the HPAI may not be spreading via migratory birds as previously thought.
What may be behind the outbreak, they said, is spring cattle movement exacerbated by the virus targeting cow udders. Milk is the only cow fluid (or tissue) where researchers have found the HPAI (an H5N1 subtype known as clade 2.3.4.4b).
“Right now, we don’t have evidence that the virus is actively replicating within the body of the cow other than the udder,” said Suelee Robbe Austerman of USDA’s National Veterinary Services Laboratory at the meeting.
Lyons added that the HPAI may be transmitted to cows via milk droplets on dairy workers’ clothing and gloves or suction cups used for milking. According to science.org, the USDA “floated” the idea that the virus may have originated on a single farm.
Science.org pointed to unidentified sources claiming some dairy farms—later shown to be infected—noticed dead cats on their properties as far back as February. The cats may have contracted the virus by consuming spilled milk.
Also, the dead birds found on infected farms were not waterfowl (which historically have spread avian flu viruses to poultry) but species such as grackles, blackbirds, and pigeons that live in and around human habitat.
As of April 2, the USDA has confirmed the HPAI (labeled H5N1 clade 2.3.4.4B) in 12 dairy herds in five states: seven in Texas, two in Kansas and one each in Idaho, Michigan and New Mexico.
Additionally, a human case of avian influenza was confirmed April 1 in a person who had contact with dairy cows presumed to be infected with the virus.
The USDA and the U.S. Food and Drug Administration continue to stress that commercial milk is safe because it has been previously pasteurized—a process that kills avian flu and other viruses.
The department recommends people not consume raw milk or products made from it.
Source: Farmtario / Jeff Melchior