Migrating birds appear to have caused a virus in dairy cattle that is causing reduced milk production.

So far, the disease, which initially started out as a bit of a mystery to state and federal officials, has been detected in Texas, New Mexico and Kansas. It has since been identified as highly pathogenic avian influenza, though officials say it does not pose a significant risk to human health.

The U.S. Department of Agriculture, the Animal and Plant Health Inspection Service, the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention, state veterinary and public health officials investigated the illness.

According to APHIS, the flu is primarily impacting older dairy cows and can cause decreased milk production and low appetite as well as other symptoms.

New Mexico State Veterinarian Dr. Samantha Uhrig said it is hard to know exactly how many dairies have been impacted because, up until recently, officials really didn’t know what pathogen they were looking for.

“We have had just a small handful of premises who have reported cattle with symptoms that were consistent with the descriptions coming out of Texas,” she said.

Because cattle are prey animals, they often hide signs of illness.

Uhrig said the most common and reliable symptoms of the avian flu in dairy cattle have been a sudden drop in milk production and decreased appetite.

She said the cattle tend to recover in a matter of days or weeks and that they really just need supportive care such as making sure they stay hydrated.

In Texas, the state’s Department of Agriculture Commissioner Sid Miller warned that impacted herds may lose up to 40 percent of their milk production for a week to 10 days, at which time the symptoms will subside.

At this point, Uhrig said there haven’t been any reports of symptoms in beef cattle either on pasture or at feedlots.

In terms of human health, Uhrig said people can be exposed to avian flu through migrating birds and, because of that, people who find deceased wild birds should report them to appropriate authorities. That could include the U.S. Fish and Wildlife Service or New Mexico Department of Game and Fish. That will allow the carcasses to be sampled.

Additionally, she said people should keep areas clean where birds might congregate.

How the virus was identified

The identification came as a result of sampling unpasteurized milk from sick cattle at two dairy farms in Kansas and one in Texas. Additionally, officials tested an oropharyngeal swab, a sample collected through the mouth from the cow’s throat, from a dairy in Texas. These tests were taken on Friday.

Deceased wild birds were also found on farms in Kansas and Texas where the avian flu has been detected.

The initial testing that has been done at the National Veterinary Services Laboratories indicates that the virus has not mutated in ways that would make it more likely to transfer to humans. APHIS says the current risks to public health remain low.

What dairy farmers should do

Uhrig said at this point officials are recommending farmers take biosecurity measures.

“Most dairy farmers are pretty good about that anyway,” she said.

Those measures could include limiting traffic onto and off of the dairy farm to just essential vehicles and making sure feed and water troughs are cleaned regularly.

Miller also recommends disinfecting vehicles entering and leaving the dairy farms and quarantining sick cattle. 

Miller’s office also encouraged dairy farmers to isolate water sources that may have been contaminated by migrating waterfowl.

Uhrig said that if dairy farmers notice cattle displaying any symptoms they should contact their herd veterinarian.

Milk supplies

Officials are telling dairy farmers to dispose of the milk produced by sick cattle. 

When it comes to commercial supplies, it is standard practice to destroy or divert the milk that is produced by sick animals.

“Dairies are required to send only milk from healthy animals into processing for human consumption; milk from impacted animals is being diverted or destroyed so that it does not enter the food supply,” APHIS said in a press release.

Additionally, the pasteurization process helps destroy any flu virus in the milk and is required before milk can be shipped across state lines.

The sick cattle are expected to recover and, unlike the outbreaks on poultry farms, officials do not anticipate dairy farmers needing to cull herds.

New Mexico is the ninth-largest milk producer and fourth-largest cheese producer in the country. Dairy farms provide billions of dollars of economic benefit to the state and the New Mexico Dairy Producers say that the industry is responsible for nearly 7 percent of the state’s gross domestic product.

New Mexico has 107 dairy farms that are responsible for 3.2 percent of the milk production in the United States. These farms tend to have more cattle than dairy farms in other states. The average dairy farm in New Mexico has 2,700 cows while the national average is 316 cattle per dairy, according to the New Mexico Dairy Producers. The vast majority of these farms are in eastern New Mexico.

Hobby farms

An increasing interest in raw milk led the City of Albuquerque to pass a raw milk ordinance that went into effect in December. This allows groceries and markets to obtain a permit to sell unpasteurized milk and unpasteurized milk products. Some hobby farmers also keep a cow or a small herd of cattle to produce raw milk for their families.

This increased interest in raw milk comes due to claims that it can reduce asthma and allergies.

According to the U.S. Centers for Disease Control and Prevention, consumption of raw milk can lead to outbreaks of illnesses and places where raw milk sales are legal have more than three times more outbreaks than areas where it is illegal to sell unpasteurized milk.

Uhrig said it is important that hobby farmers be aware of the avian flu that is impacting dairies in New Mexico. She said if hobby farmers notice any symptoms in their cattle they should report those symptoms.

She also encouraged hobby farmers to take additional biosecurity measures to protect their animals.

Avian flu and birds

The spread of avian flu tends to be higher in the spring and fall due to migrating birds.

According to an APHIS dashboard that shows how many poultry flocks have been infected over the last 30 days, two backyard flocks in Texas have had birds test positive for avian flu, impacting 330 birds.

New Mexico has not documented any cases of avian flu in either commercial or backyard poultry flocks in the past 30 days.

“We do get phone calls periodically and have followed up on investigations,” Uhrig said.

She said that New Mexico has not had a confirmed case of avian flu in backyard flocks since last fall.

Wild birds carrying the avian flu may not exhibit symptoms. Because of this, federal agencies take samples from waterfowl throughout the year. In New Mexico, a federal strategy calls for 333 samples annually from the Rio Grande-Elephant Butte watershed.