By Lynnette Harris
As the spread of Highly Pathogenic Avian Influenza (HPAI) from birds to dairy cows continues to unfold, Dr. Tom Baldwin, veterinary pathologist and director of the Utah Veterinary Diagnostic Laboratory (UVDL), wants people to remember a few key things.
“One of those things is that this virus does not kill dairy cows, nor is this an infectious disease that means the USDA has to implement mandatory slaughter,” Baldwin says. “It’s also not like some other viruses that cause more concerning problems like cows aborting their calves and it does not cripple a cow’s milk production long-term.”
Bruce Richards, assistant professor of animal science and USU Extension dairy specialist, adds that the public also needs to know that pasteurized milk and properly cooked meat are safe to consume.
Pasteurization destroys the influenza virus and other microbes in milk. Raw milk has not been through the high-temperature processing of pasteurization and carries a number of potentially dangerous microbes. Baldwin says the reason we began pasteurizing milk was to control the spread of tuberculosis.
“And since pasteurization kills those bacteria, it will certainly inactivate flu virus,” Baldwin said.
As of May 6, Colorado was the most recent state to report cows testing positive for HPAI. The American Veterinary Medical Association notes that there are 36 confirmed infected dairy herds in nine states, three of them adjacent to Utah — Idaho, Colorado, and New Mexico.
In late April, the U.S. Department of Agriculture mandated that dairy cows must be tested for HPAI within seven days of being transported across state lines whether they are going to another dairy or a livestock show.
What does HPAI look like in dairy cows?
Baldwin said one of the first things dairy farmers have noticed is a change in the cow’s manure. Most dairy cows have very loose fecal material. What farmers report is that infected animals’ manure becomes thicker. Cows also have a sharp drop in milk production.
Dr. Carmen Lau, a veterinary pathologist at the UVDL at Utah State University, noted that cows with the virus have a low-grade fever, their milk production decreases, and the quality of the milk changes, becoming thicker than normal.
The Utah Department of Agriculture and Food (UDAF) has information online about HPAI in cattle and poultry including instructions about testing animals. A statement issued by Utah’s Assistant State Veterinarian Dr. Amanda Price says dairies that suspect cows may have the virus should move sick animals to a hospital pen and immediately contact their veterinarian.
In the case of some illnesses, farmers and dairy workers bring samples they have taken directly to the UVDL for testing. Baldwin says that is not the procedure for suspected cases of HPAI. The state covers the cost of the test, but samples must be collected by a licensed veterinarian or “an approved sample collector” who has received a case number from UDAF before collecting the required milk samples.
Cow Udder Anatomy 101
A cow’s udder is comprised of four separate glands. Each gland is called a quarter.
“It’s suspected that the virus is being spread by milking machines because they have found in some cows that only one quarter is affected instead of the whole cow,” Lau explains. “It makes us suspect that maybe some milking equipment is not self-cleaning the way it should, and it’s shooting infected milk into that quarter. We don’t have proof of that right now, but virus this isn’t showing any of the classic cow-to-cow transmission.”
For example, Lau says pathologists find almost no HPAI virus in nasal secretions, so samples from nasal swabs alone are not reliable for diagnosing the infection and secretions are not likely to be a means of spreading it.
Baldwin and Lau say that while being vigilant about animal health is important, they do not advise testing animals that are clinically healthy as a random surveillance of herd health.
“If you are selling cows that are going across state lines, you test them,” Baldwin says. “Or if it appears you have a disease outbreak, you need to test.”
Lau explains that testing healthy animals as a way of looking for disease is discouraged because it is not necessary and because it would consume large quantities of laboratory supplies that are needed to diagnose sick animals, especially if there were to be a large outbreak.
Still a Virus Primarily in Birds
A lot of attention is currently focused on cross-species infections, but the virus still primarily affects birds. While it’s technically possible for humans to become infected, Lau says that to date, even workers at poultry farms are rarely infected where there are confirmed cases of HPAI and large numbers of sick and dead birds.
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