One month since Idaho first detected avian influenza in a dairy herd in Cassia County, scientists are still unraveling details about the national outbreak.
As of Wednesday, federal officials had confirmed 36 affected herds in nine states. In Idaho, two herds confirmed cases of the virus, with a third farm awaiting confirmation from lab samples.
The first farm had imported cattle from an affected operation in Texas, but the other two dairy farms, also in Cassia County, had not received cows from out of state recently.
Dr. Scott Leibsle, Idaho’s state veterinarian, said the leading theory is that the cows contracted the virus from wild birds. While scientists believe the outbreak likely originated from a single spillover event from birds to cattle earlier this year or late last year, there is some indication that the virus has since been transmitted from infected cows back to birds.
“We are working with some state and federal agencies to test some of the wild birds in the area there to see if they are carrying the virus and if the genetic makeup of the virus, if they find any in the birds, matches that in the cattle,” Leibsle said.
Federal officials suspect the virus spreads through cows’ milk, but Leibsle highlighted uncertainties like which species of birds might be infecting cattle, the duration of the illness in animals and the length of virus shedding.
Leibsle’s primary concern is on-farm production and potential financial impact on farms. To prevent outbreaks, he recommends regular sanitation of milking equipment, implementing biosecurity measures for workers and isolating symptomatic cattle.
“If a producer sees that his cattle are showing symptoms, call us and we’ll collect some samples and send them off for testing,” he said, noting that the U.S. Department of Agriculture is covering the costs of the tests.
Federal officials have said some dairy farms are obstructing agencies from testing their cattle, but Leibsle said he hasn’t run into that in Idaho.
“I don't want dairy producers to be fearful of what might happen – that the government's going to come in and shut down their dairy. That is absolutely not the case,” he said.
The milk supply
Leibsle said testing of the commercial milk supply revealed genetic material from the virus in one of five retail samples, but also showed the pasteurization process inactivates the virus.
“I think consumers should not be concerned with milk that they are buying from their retail grocery stores,” he said.
However, the risk of drinking raw milk amid the outbreak is not clear. The Food and Drug Administration emphasizes that it never recommends consuming raw milk, but in Idaho, producers can sell raw milk with a permit from the Idaho State Department of Agriculture.
“The burden really falls to the producer to be very aware, cognizant of the health of their animals,” Leibsle said.
Worker safety
The Centers for Disease Control and Prevention consider the risk to the general public from bird flu to be low, with 0nly two reported mild cases in the U.S.
“Right now, there’s very little evidence for human risk,” said Dr. Christine Hahn, Idaho’s state epidemiologist. “Nonetheless, we want to be ready; we don’t want to be complacent, so we’re talking a lot about how can we make sure we are ready should we start to see any human cases.”
However, the risk could be higher for those who work directly with cows. About 25 people have been tested for the virus and more than 100 workers exposed to sick cows have been monitored for symptoms.
Hahn said the state has not been notified of any sick workers in Idaho. She said dairy operators have been informed that the state lab can test any symptomatic worker for free.
The health department has not been visiting farms, Hahn said, but has instead been working with the Idaho Dairymen’s Association and the Idaho State Department of Agriculture to provide the latest CDC guidance in English and Spanish.
“They’re the trusted partners and know these dairy operators well,” she said.
That guidance says workers should have access to protective equipment like gloves, masks and eye shields.
