What it’s like dealing with avian influenza on a dairy farm

Glacier FarmMedia – Avian influenza is hitting American cows and dairy farms hard when they have an outbreak of the disease, say farmers who have had it on their operation.

Mortality on farms varies greatly, but some have had up to eight per cent. The number of infectious cases also varies, but can be around 20 per cent of animals.

There have been no cases found yet in Canadian dairy herds. The virus spread has slowed down recently and the outbreak is now mostly centred in California, with 97 cases in the past 30 days. Montana is the only other state with a new case in the past 30 days.

Brent Wilson, who owns Wilson Centennial Farms in Carson City, Mi. has been public about how the disease affects his herd.

H5N1 avian influenza is a reportable disease in the United States, but herds that are found to be positive with the disease are not made public.

Wilson has a leading herd and has collaborated on research over years with Michigan State University. He decided that speaking publicly and working with the researchers on the new disease was more valuable than staying silent. Because so many herds are not publicly disclosing infections, not a lot of research is being done on the disease.

His first clue that something was wrong in his herd was when herd average somatic cell count jumped to 200,000 from less than 75,000.

“All of a sudden we’ve got sick cows and we’re pumping them with electrolytes and aspirin,” he said at the recent World Dairy Expo in Madison, Wi.

Students from the Michigan State veterinary school tested his cows for eight weeks and found that 22 per cent of the cows in his 1,250 cow dairy were infected.

They are now trying to clear the herd of the infection, but milk production is down by five to seven pounds on average and their usual combined seven pounds per day of butter fat and protein combined is well down.

The cows get sick with influenza-like symptoms, can go off feed, have runny noses, often develop mastitis and have increased abortions and cows that are already thin or compromised have less chance of recovering.

“I’ve lost a tremendous amount of peak lactations. We’ve experienced abortions, particularly in later lactation cows,” he said.

Wilson is worried how those cows will perform in the next lactation.

That’s a concern across the United States and researchers like Dr. Jason Lombard, from Colorado State University, are trying to answer those questions about a fast-evolving, new disease.

Immunocompromised cows are more affected, Lombard said at the World Dairy Expo. That includes cows who are pregnant, which explains why there are more abortions in cows with avian influenza.

Lots to learn

Lombard has researched how the disease is transmitted and there are still many questions to answer. Researchers swabbed 126 places on milk trucks in Michigan leaving infected farms and found only one positive test for the virus, so trucks are not considered a major vector for the disease.

He cautioned that trucks could be found to be an issue elsewhere.

Movement of wild birds has also been ruled out in the spread of the disease. Some poultry on farms near to infected dairy farms have tested positive, but it’s believed that the infection came from the dairy to the poultry barn.

The biggest remaining question is whether the virus moves through the air – termed aerosol spread.

“We haven’t been able to really prove that aerosol spread is an issue,” he says, but testing shows that most animals in a herd are exposed even if they don’t get sick, which would suggest potential aerosol spread. There are also closed herds, which have imported no cattle and share no workers which have also broken with the virus, which would also suggest potential aerosol spread.

Testing or not?

Some dairy farmers like Brian Pacheco who owns Pacheco Dairy in Fresno, Cali., have decided to test cows each week for H5N1.

The first case in California was 10 miles from his farm. A group of cows from California had been sold to Iowa. For whatever reason, some were sent back to California and were resold into three herds. The cows had brought the disease back from Iowa.

Pacheco milks about 1,400 cows and has a herd of 100 top Brown Swiss cows. He hasn’t bought or added cows to his farm for years.

However, he’s identified other risk factors, including cattle destined for beef leaving the herd on a weekly basis. Those truck tires are sprayed entering and leaving the farm and workers coming onto the farm wear disposable boots and gloves. His workers only work on his farm.

“We try to be reasonable and practical on what we have to do,” he said at the World Dairy Expo.

He says on a friend’s dairy with 2,500 cows with an outbreak, they drench 400 cows per day, which means a crew working from 7 a.m. to 4 p.m. and bringing in totes of electrolytes.

He’s eager to avoid that situation, so has decided to test his herd. That creates some concern, but he’s decided it’s worth it.

“I wait with anxious anxiety each week” for the results of the tests, he says. So far, in dairy-dense Fresno County, his herd is still negative for H5N1.

World Dairy Expo still went on

In another area of the United States with a lot of cows, Wisconsin, home of the World Dairy Expo which brings thousands of people and cows together from around the world, there have been still no positive reported cases of H5N1 in dairy cows.

Dr. Keith Poulsen, an associate professor in the University of Wisconsin school of veterinary medicine, and the person in charge of veterinary care for the cows at the World Dairy Expo, says that value of the expo in terms of genetics sales, and in being together as a community, along with the fact that there had not been a case in Wisconsin, meant that the show had to go on.

Cattle had to be tested for H5N1 before they could arrive at the show, and they had to be quarantined when they leave, especially those returning to Canada.