HPAI Cases Investigation Continues

Researchers Continue to Look for Transmission Source of Influenza in Dairy Cows

Jennifer Carrico
By  Jennifer Carrico , Senior Livestock Editor
Dairy cows in several states have become infected with influenza, leading to loss in milk production and profits. (DTN/Progressive Farmer file photo by Jennifer Carrico)

REDFIELD, Iowa (DTN) -- As the influenza virus is found in more dairy herds in several states, veterinarians and researchers continue to find out more about the illness. So far, no cows have died, but the virus already has caused about 20% income loss in affected operations.

"I hate to compare this to COVID, but as we find out new things every day, I feel like it's the same thing we heard during the pandemic," said Fred Gingrich, executive director of the American Association of Bovine Practitioners. "We are finding out new things daily about this virus and how it's affecting infected dairy cows. We didn't know anything about this until now."

Gingrich said influenza in animals is treated the same as it is in people, with supportive care. There's no real treatment since it is a virus. Instead, cows are given extra fluids, offered proper nutrition, and given anti-inflammatory medicines if a secondary infection is found such as mastitis or pneumonia.

"I think the poultry people would really prefer we don't call it 'highly pathogenic avian influenza' because HPAI is killing a lot of birds, and what we are seeing in dairy cows is not doing this," Gingrich said. "These cows are positive for influenza A, which is what they are being tested for."

Affected dairy cows are reported as being off feed, which is likely the first indication of sickness. Their milk is thick, and thus, they are getting pulled from the milking herd and usually tested first for mastitis. Their manure appears tacky during this sickness.

"Cows are pulled on day two to five and put in the hospital pen for surveillance and treatment. It seems to be affecting about 10% of the herd, and by day 14 to 21, the cows have recovered," he added. "A decrease in milk production is a big effect on these herds. We will see up to a 20-pound loss in production per cow, which, in the end, is a 20% loss in income for these producers."


Drew Magstadt, clinical associate professor at Iowa State University's College of Veterinary Medicine, said samples have been sent to the Veterinary Diagnostic Laboratory in Ames to be screened for influenza A, which is also common in poultry and hogs.

"We can test serum samples, blood samples, or nasal samples. Since we also run these tests on poultry and hogs, we run the tests more often than some other labs," Magstadt said. "We are looking for influenza antibodies in these samples, and once we have the results, that is reported back to the submitting veterinarian."

He said they continue to ask for samples from herds that have been affected to determine how many cows are infected. These results can help to determine routes of transmission.

"We would like the test results to be able to help the herd veterinarians determine if all the cows affected are in one pen or if they are randomly around the barn," Magstadt said. "Knowing what age of cows are showing the symptoms is important also. The results can help us know if there is any kind of cow-to-cow transmission or if it is strictly a bird-to-cow transmission."

The Ames lab is only one of several labs performing the tests. Magstadt said there is a network where information is shared on what is being found and communication between labs has been helpful for all the researchers.


Milk from cows with any kind of sickness is diverted from the milk sold for commercial use. Gingrich said producers have their own protocols they follow to deal with waste milk. This could be by either dumping the milk with none of it being used at all or pasteurizing the milk to be fed to calves.

Jamie Jonker, chief science officer for the National Milk Producers Federation, said there continues to be no concern about the safety of the milk supply or that this circumstance poses a risk to consumer health because products are pasteurized before entering the market, per the Food and Drug Administration.

"Pasteurization has continually proven to inactivate bacteria and viruses, including influenza in milk," he said. "All dairy cattle are also subject to the Federal Meat Inspection Act and must be slaughtered and processed under inspection by USDA's Food Safety and Inspection Service, ensuring that all meat entering the food supply has been inspected and approved for human consumption."

No cows have died from being affected by influenza A, and no herds have been depopulated as has happened with HPAI in the poultry flocks due to spreading and death in the birds.

Gingrich stressed the importance for all dairy producers to work with their herd veterinarian on buttoning up biosecurity. A bird deterrent plan is important, and feed should be covered to prevent virus contamination.

"Producers need to look at everything that is coming into their operation -- people, feed trucks, milk trucks, and breeders. A disinfection protocol should be in place for all those who need to come in. Nonessential people need to just stay out right now," he said. "Herd purchases should be put on hold, if possible, until we know how this virus is transmitted."

Gingrich said that while there haven't been any cases found in the beef herd, it is important to have continued surveillance of these animals. If several cattle in feedlots are being pulled to the hospital pen because of a decrease in feed intake, he suggests performing influenza tests. Cow-calf herd producers should look for indications of decreased milk production through observing hungry or sick calves.

"We really don't know if we will see it in the beef herd, but it never hurts to be on the alert," he added.


Gingrich said there is a lot of fear in the industry. He suggests dairy producers don't try to hide any health problems they may be dealing with, as the more samples achieved from cows with symptoms, the more that will be learned about the epidemiology of the virus.

"If we can't learn something from this influenza virus in our cows, then what are we going to do if a worse disease hits the herd?" he stressed.

It's also important for farmers and the public to realize this virus is easy to kill.

"There's a low risk for people to get this virus, but it can happen, and dairy farm workers should take precautions by using gloves and eye protection, as well as cleaning their hands often," he said.

Another important factor is to refrain from consuming or selling unpasteurized milk. Calves should only be fed pasteurized milk as well. The virus is destroyed by heat.

Jonker said federal and state animal health officials are diligently working with private veterinarians and dairy farmers to investigate influenza on dairy farms.

"The collaboration is ensuring a coordinated response fielding valuable information about the disease etiology and biosecurity measures dairy farmers can take to reduce the risk for their herds," he said.

Information is learned daily from the data being collected and analyzed with hopes of knowing more about transmission and how mammals are affected.

"So much with something like this is unknown. This is so different than anything we've dealt with before and we are learning a lot each day," Magstadt said.

For the latest on confirmed cases of HPAI in dairy cattle, see "Ohio Dairy Tests Positive for HPAI" here: https://www.dtnpf.com/….

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

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Jennifer Carrico