US Scientists to Investigate Possible Respiratory Spread of Bird Flu in Cows

Chickens walk in a fenced pasture at a farm in Iowa, on Oct. 21, 2015. (Charlie Neibergall/AP Photo)

U.S. federal and state agencies are planning research into the potential respiratory spread of the highly pathogenic avian influenza among dairy cattle, with the hope that the research will guide efforts to contain the influenza—known as the bird flu—and reduce exposure to humans.

The Michigan Department of Agriculture and Rural Development is working with Michigan State University and the U.S. Department of Agriculture (USDA) to plan research on farms to evaluate respiratory spread, according to Tim Boring, the department’s director.

“This is an area of concern that we’re building out and looking more into,” Mr. Boring said. The research is a high priority and will be important to guiding the state’s public policy, he said.

A spokesperson for the USDA said the agency is researching respiratory infection in dairy cows with partners that include universities across the country to better understand the virus and control its spread.

The USDA had previously said that scientists had “not found significant concentration of virus in respiratory-related samples, which indicates to us that respiratory transmission is not a primary means of transmission”

The flu has sickened cows in 86 herds across 12 states, most recently Wyoming, as well as three people and numerous birds. Scientists have so far suspected the virus spreads among animals and humans through contact with infected milk or aerosolized milk droplets, or from exposure to infected birds or poultry. But the exact mechanics of the spread of the virus are still unclear, though there is evidence of spread to cows from wild birds and other cows.

The virus has been identified mainly in milk, but also in nasal swabs at lesser levels, said Zelmar Rodriguez, a dairy veterinarian and assistant professor at Michigan State University’s College of Veterinary Medicine who has researched affected farms.

“If it’s present in the nose when the cow is shedding, it’s potentially transmitted through air,” he said.

The first human patients, one each in Texas and Michigan, only suffered inflamed eyes, or conjunctivitis.

The most recent human infection, also in Michigan, was the first “to report more typical symptoms of acute respiratory illness associated with influenza virus infection,” according to the U.S. Centers for Disease Control and Prevention. Those included a cough.

Any change in how the virus is transmitted gives it the opportunity to evolve, said Richard Webby, a St. Jude Children’s Research Hospital virologist who studies flu in animals and birds for the World Health Organization.

“We certainly don’t want that,” Mr. Webby said.

But for the virus to be a more significant threat to human health, it would need to undergo further genetic mutations, he said.

Analyses of samples from the human cases have shown several mutations, according to the CDC. But to date, the circulating bird flu viruses “do not have the ability to efficiently bind to receptors that predominate in the human upper respiratory tract,” which is a major reason the agency pegs the risk to the public as low.

The CDC says that influenza viruses can “rapidly evolve,” making the identification of cases and preparing for more spread essential. More than 500 people have been monitored after being exposed to animals with confirmed or suspected infections, and at least 45 of those people, all of whom developed flu-like symptoms, were tested.

The CDC recommends that all people with exposure and symptoms monitor themselves for symptoms for 10 days. Health officials should get involved if those exposed weren’t wearing personal protective equipment such as masks when interacting with sick or potentially sick animals.

Symptoms consistent with the bird flu include fever, cough, and vomiting, according to the CDC. If people start showing symptoms, they should be tested and possibly isolate for a period of time in addition to receiving treatment, the agency advises. The common flu treatment Tamiflu, or oseltamivir, works against the bird flu, particularly when given soon after symptoms appear, officials say.

The first cattle with detected infections in the United States, in Texas earlier this year, showed respiratory symptoms, officials say. Researchers with the University of Texas Medical Branch and other institutions reported in a new study that the virus was more prevalent in nasal swab samples from the cattle, versus rectal swab samples, “supporting the notion that the respiratory tract of cattle could be involved in cow-to-cow transmission.”

Other animals sickened by the bird flu in recent years include cats, bears, and foxes.

Some of those animals have shown respiratory symptoms, according to the CDC and the World Organisation for Animal Health.

The CDC said this month it infected six ferrets with the bird flu and all died. The virus “spread efficiently between ferrets in direct contact but did not spread efficiently between ferrets via respiratory droplets,” the agency said. “This is different from what is seen with seasonal flu, which infects 100 percent of ferrets via respiratory droplets.”

Reuters contributed to this report.