Surveilling for HPAI key to reducing spread

PLOVER, Wis. — In the seven months that have passed since highly pathogenic avian influenza was confirmed to be affecting dairy cattle in the U.S., there are still questions for dairy producers around the country.

Mitigating risks of HPAI on dairy farms was a topic at the Professional Dairy Producers Herdsperson Workshop Oct. 29 in Plover. Dr. Keith Poulsen presented. Poulsen is the director of the Wisconsin Veterinary Diagnostic Laboratory, which is a Level 1 National Animal Health Laboratory Network.

“Biosecurity and surveillance are the most important part for dairy farmers, especially for what is happening right now with the flu,” Poulsen said.

As of Nov. 6, incidents of HPAI in dairy farms has been limited to three states, California, Idaho and Utah, having positive tests in the past 30 days. Poulsen said that statistic does not paint a clear picture of what is happening.

California has had 150 newly affected herds in the past 30 days, with 233 positive herds overall. Utah, which had previously been free of confirmed cases, had nine herd confirmed positive for the virus since Oct. 31. 

“California is exploding right now,” Poulsen said. “The same thing happened in Colorado when they started testing, but California is quite different.”

Poulsen explained that while the virus spread quickly in Colorado, geography played into that.

“Colorado has about 100 dairies,” Poulsen said. “Eighty-five of those are in two counties in the state’s northeast corner. The rest are on the other side of the Rockies. In California, we have seen the virus start in the southern Tulare Valley and now it is moving up into the Modesto and Turlock areas.”

According to Poulsen, there is movement of cattle between California and Idaho, which might account for the two positive cases Idaho has experienced in the past 30 days.

Since the original confirmation of the disease in March, there have been 443 affected herds spread across 15 states: California, Colorado, Idaho, Michigan, Texas, Iowa, New Mexico, Minnesota, South Dakota, Kansas, Oklahoma, Wyoming, North Carolina, Ohio and Utah.

The questions that remain about the virus show the crucial role of biosecurity and surveillance in mitigating risk, Poulsen said.

“We don’t know exactly how this virus is moving,” Poulsen said. “Movement of animals, shared equipment and movement of people seem to be the three most common things moving this virus. We shouldn’t be limiting our thinking to just this virus. What about (bovine viral diarrhea), salmonella or the next coronavirus?”

Poulsen chronicled studies that have debunked conventional logic about the transmission of the disease.

One study placed an affected and non-affected cow together in a pen. The same milker was used first on the affected cow then moved to the non-affected cow. The virus did not move to the second cow.

Another study placed the virus in the nose of a calf that was placed with other sentinel calves. It did not spread from calf to calf.

A milk truck was thoroughly swabbed on the outside, with no detection of virus, while the virus was detected on surfaces inside the milking parlors of the farms where the truck picked milk up.

“Our infection models aren’t accurate,” Poulsen said. “They don’t mimic what happens on a 5,000-cow dairy.”

Poulsen urges dairy producers to take part in surveillance as a method of controlling the disease and potentially changing management decisions relating to affected animals.

Poulsen said a herd in Idaho began daily bulk tank surveillance as neighboring dairies were experiencing infection. The bulk tank polymerase chain reaction test was looking for nucleic acid, pieces of virus as opposed to live virus. Virus ribonucleic acid was found in the bulk tank PCR two weeks before animals in the herd began to exhibit clinical symptoms.

“When you have flu, COVID or whatever is going through the school or day care, you’re going to be shedding virus long before you have clinical signs,” Poulsen said. “That’s what makes biosecurity important — it’s too late at the onset of clinical symptoms. When you see PCR in the bulk tank, you know in about 10 days you’re going to start seeing clinically affected cows. That’s key — it could change how you move animals on and off your farm, how you manage cattle in the parlor.”

Poulsen talked about the roadblocks that contribute to farmer resistance to surveilling for H5N1.

“I have talked to farmers who have said they would like to help, but they fear losing their milk market,” Poulsen said. “We have never once — not one farm — lost a milk market. That is because pasteurization is 100% effective. The Pasteurized Milk Ordinance is 100 years old. It was started to control (bovine tuberculosis) in milk. If a herd comes up with TB, and there are a couple every year, they still sell milk because it’s pasteurized. TB is 100 times stronger than flu. Fear should not be a reason.”

It is challenging to put a national surveillance effort in place, Poulsen said.

“This is an animal problem, not a food problem,” Poulsen said. “That is why it is so difficult to get things moving and be effective, allowing us to have business continuity. It’s complicated.”

Officially, milk in the cow is considered an animal problem, and is under the U.S. Department of Agriculture’s jurisdiction. Milk in the tank is a Grade A milk problem, which is under the Food and Drug Administration. The people that work on the farm, are under the Centers for Disease Control and Prevention. States also differ in how they handle it.

“The American Veterinary Medical Association and the American Association of Bovine Practitioners agree that this is a national consensus issue, and in order to eliminate this virus, we have to start with better surveillance,” Poulsen said.

Poulsen said there is little surveillance effort in Wisconsin, with only four herds — all managed by the University of Wisconsin — being surveilled.

“We know our industry is a national industry, not a Wisconsin industry,” Poulsen said. “National surveillance allows us to recognize and put resources where we need them. We need people on the ground, on the front lines, making decisions. Right now, those decisions are being made by people in Washington, and that is a big problem.”