Bird flu virus in milk poses challenges for dairy industry

The discovery of bird flu virus fragments in milk sold in U.S. stores, including about 20% of samples in initial testing, suggests that the H5N1 virus may be more widespread in U.S. dairy cattle. what was previously known. Photo by Scott Bauer/Agricultural Research Service

April 26 (UPI) — The discovery of bird flu virus fragments in milk sold in U.S. stores, including about 20% of samples in initial nationwide testing, suggests the H5N1 virus may be more widespread in dairy cattle than previously thought.

The Food and Drug Administration, which announced the first results of its nationally representative sampling on Thursday, was quick to emphasize that it believes the commercial milk supply is safe. However, the highly pathogenic avian influenza virus can make cows sick, and the presence of the flu virus in herds in several states and new federal restrictions on the movement of dairy cows between states are putting economic pressure on farmers.

Five livestock infectious disease experts from the University of California, Davis (Noelia Silva del Rio, Terry Lehenbauer, Richard Pereira, Robert Moeller and Todd Cornish) explain what the test results mean, how bird flu can spread to livestock and the impact on the industry.

What are avian flu viral fragments and can they pose risks to people?

It is critical to understand that the presence of H5N1 viral fragments does not indicate the presence of intact viral particles that could cause disease.

The commercial milk supply maintains safety through two critical measures:

• Firstly, milk from sick animals is quickly diverted or disposed of, ensuring it does not enter the food chain.
• Second, all milk sold in grocery stores is heat treated to reduce the pathogen load to safe levels, primarily through pasteurization. Pasteurization has been shown to effectively inactivate H5N1 in eggs, and that process occurs at a lower temperature than that used for milk.

The viral fragments were detected using the quantitative polymerase chain reaction test, known for its exceptional sensitivity in detecting even traces of viral genetic material. These fragments are just evidence that the virus was present in the milk. They are not evidence that the virus is biologically active.

To assess whether the presence of viral fragments corresponds to a virus capable of replicating and causing disease, a different testing approach is necessary. Tests such as embryonated egg viability studies allow scientists to evaluate the virus’s ability to replicate by injecting a sample into an embryonated chicken egg. Those types of tests are underway.

On Wednesday, the FDA said it had found no reason to change its assessment that the U.S. milk supply is safe. The agency strongly advises against the consumption of raw milk and raw milk products due to their inherent risks of contamination with harmful pathogens, including avian flu viruses.

How does the bird flu virus get into cow’s milk?

Currently, cows with confirmed H5N1 have different symptoms than the typical flu-like symptoms seen in birds.

Abnormal milk and mastitis, an inflammatory response to infection, are common. While it is speculated that other body secretions, such as saliva, respiratory fluids, urine or feces, may also harbor the virus, this has not yet been confirmed.

How waterfowl or other birds transmitted H5N1 to livestock is still being investigated. In 2015, an outbreak of highly pathogenic avian influenza on commercial poultry farms peaked in April and May, at the same time birds were migrating north. Birds can shed the virus through oral, nasal, urinary and fecal secretions. Therefore, the virus could potentially be transmitted through direct contact, ingestion of contaminated food or water, or inhalation of the virus.

Infected dairy cows can shed the virus through their milk and can probably transmit it to other cows, but that remains to be proven.

Contagious pathogens that cause mastitis can be transmitted through contaminated milking equipment or milking gloves. Ongoing research will help determine whether this is also a possible transmission route for H5N1 and, if so, what causes the virus to thrive in breast tissue.

If H5N1 is found to be widespread in milk, what risks could it pose to the dairy industry?

For the dairy industry, infection of livestock with the H5N1 avian influenza virus creates challenges on two levels.

The primary concern is always the safety and healthfulness of milk and dairy products.

State and federal regulations and existing industry practices require that sick cows or cows with abnormal milk be separated so their milk does not enter the food supply. Proper pasteurization should kill the virus so that it cannot cause infection.

The American Association of Bovine Practitioners has also developed biosecurity guidelines for H5N1, focusing on key practices. These include minimizing contact of wild birds with livestock and their environment, managing the movement of livestock between farms, isolating affected animals, avoiding feeding unpasteurized (raw) colostrum or milk to calves and other mammals, and ensuring the use of personal protective equipment for animals. caregivers.

The other major concern is the health of the dairy herd and the people who care for the dairy cattle. A farm worker handling dairy cows contracted H5N1 in Texas in March, but such cases are rare.

There are no specific vaccines or therapies available for avian influenza infections in dairy cattle. But following good sanitation and biosecurity practices for both people and cows will help reduce the risk of exposure and spread of the avian influenza virus among dairy cattle.

For cows that contract the virus, providing supportive care, including fluids and fever reducers as needed, can help them overcome the illness, which can also cause loss of appetite and affect their milk production.

Dairy farms facing an outbreak will suffer financial losses from caring for sick animals and temporarily reduced milk sales. According to early estimates, approximately 5% to 20% of animals in affected herds have become ill. Affected animals usually recover within 10 to 20 days.

At least 22 states have restricted the importation of dairy cattle to prevent the spread of the virus, and the federal government announced that it will require testing of lactating dairy cattle before they can be moved between states starting April 29, 2024. Yes Although the overall impact on U.S. milk production is expected to be lower annually, it could result in short-term supply disruptions.

How worried should people be about bird flu?

The federal government’s food safety and monitoring measures, along with pasteurization, provide important safeguards to protect the public from potential exposure to the avian influenza virus through the food chain.

However, drinking raw milk poses a risk of exposure to multiple diseases, including H5N1. That’s why the FDA and the Centers for Disease Control and Prevention strongly recommend drinking only pasteurized milk and dairy products.

Noelia Silva del Río is an associate specialist in cooperative extension, production medicine and food security at the University of California, Davis; Richard V. Pereira is an associate professor of veterinary medicine and associate agronomist at the University of California, Davis; Robert B. Moeller is a professor of veterinary medicine at the University of California, Davis; Terry W. Lehenbauer is a professor of veterinary medicine at the University of California, Davis, and Todd Cornish is a professor of veterinary medicine at the University of California, Davis.

This article is republished from The Conversation under a Creative Commons license. Read the original article.