BIOSECURITYUSDA Reports Reveal Biosecurity Risks at H5N1-Affected Dairy Farms
Shared equipment and shared personnel working on multiple dairy farms are some of the main risk factors for ongoing spread of highly pathogenic H5N1 avian flu in dairy cows, the US Department of Agriculture (USDA) said today in a pair of new epidemiologic reports.
Shared equipment and shared personnel working on multiple dairy farms are some of the main risk factors for ongoing spread of highly pathogenic H5N1 avian flu in dairy cows, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) said today in a pair of new epidemiologic reports.
One of the reports is an overview based on the results of questionnaires from affected dairy herds, and the other is a deep dive into the dairy cow and poultry outbreaks in Michigan, the state hit hardest by outbreaks in dairy cows, which now number at least 94.
At a media briefing today, Kammy Johnson, DVM, PhD, a veterinary epidemiologist with APHIS, said the multistate epi report provides a national clinical picture of the disease in cows and the routes of spread, and the report from Michigan is an early snapshot showing what’s happening in the field.
Both suggest three key factors for transmission between farms: shared equipment and vehicles, shared personnel who may inadvertently carry the virus between farms on their clothes or boots, and animal movements. “The bigger picture is that enhanced biosecurity is really critical,” she said.
So far, genomic evidence continues to suggest a single introduction from wild birds, with further spread among dairy farms, such as from Texas to Michigan in the initial weeks of the outbreak. Now the virus is spreading between farms owing to multiple direct and indirect factors, according to the APHIS reports.
Multiple Factors Fuel Spread Between Farms
Questionnaires revealed that more than 20% of farms received cattle within 30 days of clinical signs, and 60% of farms continued to move cattle off the facilities after animals showed signs of illness.
Most farms had cats present, and more than 50% of those had sick or dead cats. Also, more than 20% of dairy farms also had chickens or poultry, nearly all of which had sick or dead birds. USDA officials said cats are the canary in the coalmine, but cats and other animals, such as wild birds, probably aren’t playing a major role in the spread of the virus, though they could serve as fomites.
Clinically, lactating cows are the most affected, with signs of illness in less than 10% of herds and mortality and culling averaging less than 2%.
