What does HPAI look like in dairy cattle?

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Editor’s note: As of April 8, the Association of Bovine Practitioners is referring to an HPAI infection in cattle as BIAV: bovine influenza A virus.

For the first time, highly pathogenic avian influenza (HPAI) has been confirmed in dairy cows. Cattle in the Texas panhandle first tested positive for the virus, but more dairy cattle have tested positive in other states, including Michigan and Ohio, since the initial finding. At this time, there have been no reported cases in dairy or beef cattle in Canada.

HPAI virus is largely fatal in chickens and turkeys and for many wild bird species that carry and spread the disease along migratory routes.

Veterinarians in the U.S. are learning more about how HPAI presents in dairy cattle, but there are still many unknowns as to how the virus spreads between animals.

The National Milk Producers Federation hosted a webinar to share multiple perspectives on what is known — and not known — about the disease. Brandon Treichler, DVM, was part of a team presenting the most recent findings of how HPAI has presented in dairy cattle to date. He has been working directly with herds impacted by the disease.

What is known, based on the herds in the U.S., is that symptoms of the disease include a significant decrease in rumen activity, decreased feed intake, a significant drop in milk production, changes in milk consistency, and changes in manure texture.

Treichler says that the drop in rumen activity can be seen on tracking collars very quickly and is stark. Manure becomes dry, likely due to decreased fluid intake. Supportive care, including supplementary fluids, has proven most effective, he says. Antibiotics are not required unless a secondary infection occurs.

Not all infected cattle present with a fever. Older, mid-lactation cows seem to be more impacted in terms of severity, but younger animals have still tested positive. One, a few or all quarters of the udder may see a change in milk consistency, with milk becoming thicker and more yellow, similar to colostrum. At this time, some cows have dried off during the 10 to 14 days of sickness and have not returned to lactation. Initially, this led to culling heavily, prior to producers or vets knowing that HPAI was the cause.

Positive tests have been drawn from milk samples — unpasteurized milk and colostrum should not be consumed by calves (or humans) as a precaution. Pasteurization kills any pathogen present. Meat and milk from sick animals is highly unlikely to have entered the food chain, however, risk to human health of any exposure is extremely low. To date, no positive HPAI tests have been drawn from meat.

Producers are encouraged to step up biosecurity protocols to not only limit animal exposure to birds and bird droppings, but also to cattle from other farms. Limiting people movement, adhering to sanitation protocols on shared equipment, i.e. trailers, is also recommended, however, at this time there isn’t a full understanding of how HPAI spreads between animals.

In Canada, while no cattle have yet tested positive, migratory birds that may carry HPAI are already overhead. Producers have been alerted to symptoms to watch for and are encouraged to call their vet if they suspect HPAI. All producers are encouraged to review and implement biosecurity measures.

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