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HPAI Dairy Herd Infection Case Report

By Phil Durst

May 1, 2024 marked day one of the onset of an outbreak of Highly Pathogenic Avian Influenza (HPAI) on one dairy farm in Michigan. The farmer, recognizing the potential benefit to other farmers, willingly shared this information and agreed to have official testing of his herd. This report is what was known and reported on day 15 of the HPAI infection in a herd of approximately 500 lactating cows. Prior to infection, the average cow production on this farm ranged from 95 to 100 lbs. per day.  

Initial symptoms were detected with the SmaXtec monitoring boluses that they currently have in about 90% of lactating cows. The onset was manifested by a spike in body temperature of 4 to 5 degrees above normal, followed by a decrease in rumination 6 hours later. Rumination decreases were typically 8% or more in affected cows.

The temperature elevation lasted about two days, resulting in severe dehydration. The farm took an aggressive approach to supportive therapy, administering aspirin boluses twice a day to reduce temperature and inflammation and providing IV hypertonic fluids and Vitamin B in some cases. They tried IV Banamine on a limited number of cows but did not see any positive impact. Their goal is to make the cows as comfortable as possible.

It began in a barn with two pens of cattle that had three water fountains, the center one being shared. They wanted to try to confine the disease to a single group or at least a single barn. They changed their wash cycle in milking so that it washed after this group of cows. Regardless of their efforts, HPAI spread to all groups of lactating cattle on the farm.

For the first nine days, milk production per cow only decreased by about 5 lbs. and were optimistic they had beaten back the disease. However, by day 12 each cow was producing 21 lbs. less than average, accompanied by a doubling of somatic cell count to 180,000 c/ml. Cows were dehydrated with sunken eyes. Day 15 was the first day that the monitoring report showed fewer cows affected than the day before. Based on the number of cows with elevated temperatures and subtracting out the normal rate, they believe 40% of the lactating herd was infected.

The number of cows the farm employees needed to handle in some way had increased sixfold, making the work very labor intensive. They stopped breeding heifer and dry cows because of the demands working with sick cattle.

While pregnancy checks have not at this point shown a reduction in conception, a few late-lactating cows aborted their calves, likely due to high body temperatures. The disease primarily affected high-producing, multi-lactation cows and the low group. Transition cows seem to be performing normally at this point. Waste milk is pasteurized before feeding it to calves, and to date, the calves seem to be doing fine.

Employees have stayed healthy so far. The farmer encouraged them to wash their hands frequently and avoid touching their face and eyes. All employees were offered safety eyewear or face shields.

Clearly, by day 15, the full impact of the disease has not yet been felt. However, the farmer did some cost estimations. He has spent $5,000 – $7,500 in extra medical supplies. Even though the costs of these common medications are low, the volume needed has been quite high. There has been the loss of milk, loss of quality premium, increased labor and loss of a few pregnancies resulting in culling animals. He estimates the cost for this herd of approximately 500 cows at $30,000 – $40,000.

The owner of the farm in this case report understands that this does not include the potential longer-term costs. Another farmer said that some herds are seeing symptoms for four to six weeks. Additional negative impacts include increased culls of animals that do not recover significantly and increased weight gain of late lactation cows that recover feed intake but not milk output.

“It has been a lot of work, stressful on the cows and frankly overwhelming,” the farmer said.

As required by law, this farmer reported the disease to the Michigan Department of Agriculture and Rural Development (MDARD). He believes it is important for the industry to understand the disease. He knows that his is not the only farm to get HPAI and hopes that the more we can learn from his experience, the better we can prevent more herd infections, reduce the impact and potentially be better prepared against other diseases.

Michigan State University Extension is a leader in working with this and other farms regarding HPAI for the benefit of the dairy industry and provides resources at our animal agriculture and avian influenza websites.

Source : msu.edu

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