Highly pathogenic avian influenza now in 28 dairy herds in 8 states

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A holstein cow looks through a fence.

SALEM, Ohio — Highly pathogenic avian influenza has now been detected in dairy cows in eight states, prompting some states to restrict cattle movements.

The U.S. Department of Agriculture confirmed on April 9 that dairy herds in North Carolina and South Dakota tested positive for HPAI, or bird flu.

The Michigan Department of Agriculture and Rural Development announced on April 12 three more HPAI cases were detected in dairy herds in three additional counties — Ionia, Isabella and Ottawa. The first detection in Michigan was in Montcalm County on March 29.

In all, 28 dairy herds have tested positive for HPAI: 11 herds in Texas, six in New Mexico, three in Kansas, four in Michigan, and one each in Ohio, Idaho, North Carolina and South Dakota. 

South Dakota and North Carolina officials did not say if the affected herds had received cows from an earlier-affected state. The first herds affected by the outbreak in Texas and Kansas, announced by the USDA on March 25, are believed to have picked it up from wild birds, which carry the disease without showing symptoms. 

The positive herd in Ohio and the first positive herd in Michigan tested positive for HPAI after receiving cows from affected herds in Texas that were not yet showing symptoms. It’s not clear how the more recent positive herds in Michigan contracted the virus.

Restrictions

The USDA has not yet issued federal quarantine orders, but strongly recommends producers minimize the movement of cattle and test cattle for influenza before making necessary movements. 

Meanwhile, Pennsylvania, West Virginia and 15 other states have placed various restrictions on cattle imports. 

The Pennsylvania Department of Agriculture issued a quarantine order on April 6 for interstate and international cattle movements. Dairy cattle coming into Pennsylvania from a state where HPAI-positive cattle were found must be tested for Influenza A five days before movement. 

West Virginia requires a certificate of veterinary inspection for dairy cattle coming from a state with a confirmed HPAI detection in dairy cattle in the past 30 days.

The Ohio Department of Agriculture has not issued any movement restrictions or testing requirements related to the HPAI outbreak in cattle.

Impact

HPAI isn’t fatal in dairy cows like it is with domesticated poultry. More than 85 million birds in the U.S. have died from the disease or been culled to stop the spread since the current outbreak began in February 2022.

Most infected cows recover with supportive care, although they may be dried off. The symptoms of HPAI in dairy cows are a sudden drop in milk production, producing a thick, colostrum-like milk, decreased appetite, fever and unusual stools.

It’s still not clear how the virus, now deemed bovine influenza A by the American Association of Bovine Practitioners, is transmitted in cows. The primary mode of transmission appears to be from wild birds as they migrate. But there is also evidence to suggest the virus is being transmitted from cow to cow. Infected cattle shed the most virus in milk, but it can also be detected in the respiratory tract.

There is no safety risk to the commercial milk supply as pasteurization inactivates the virus and sick cows are milked separately, as part of standard practice and in line with federal regulations.

The Food and Drug Administration warned producers not to manufacture or sell raw milk or raw milk cheese products made with milk from cows showing symptoms of illness. The FDA’s longstanding position is that unpasteurized, raw milk can harbor dangerous microorganisms that can pose serious health risks to consumer

Producers are urged to practice good biosecurity and update plans. The National Milk Producers Federation released HPAI-specific biosecurity recommendations that can be found here.

Additionally, dairy producers who notice unusual clinical symptoms in their animals should contact their herd veterinarians.

The Pennsylvania Center for Dairy Excellence is hosting weekly conference calls on Wednesdays at 1 p.m. to share regular updates on this evolving situation. The next call will be held on April 17 at 1 p.m. Click here to register or learn more about the call.

Related content:

Biosecurity kits available for Pennsylvania dairy farmers

Ohio dairy herd tests positive for HPAI

Dairy cows in Michigan diagnosed with bird flu

Bird flu detected in dairy cows in Texas, Kansas

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