While New York state has not had a case of avian influenza in dairy cows, veterinary experts say milk testing underway at dairy processing plants is the key to early detection. According to the Centers for Disease Control and Prevention, no person-to-person spread of avian flu H5N1 virus has occurred, however 70 people in the US have become infected from live poultry, cattle, or milk directly from the milking process.
With dairy farms expanding into larger numbers of cows, Kaitlyn Lutz, VMD, bilingual dairy specialist for Cornell Cooperative Northwest Dairy Livestock and Field Crops Team, said milk testing is able to keep pace. She said pasteurizing milk with heat at processing plants has been demonstrated to kill the H5N1 virus before milk is sold for human consumption.
“It’s actually kind of a wimpy virus when it comes to heat treatment,” said Michael Capel, DVM, DABVP, a bovine veterinarian and partner in Perry Veterinary Clinic in Wyoming County. “Pasteurization is 100% effective.”
While dabbling ducks like mallards introduced avian flu to cows, the virus has changed to a new strain that moves within cattle, and occasionally to people. Eliminating contact between cows and birds is not a prevention priority.
“The original spillover event was from wild birds to dairy cattle, but now that it’s been in cattle, it’s thought that it is spread from other infected cattle or fomites (secretions),” Lutz said. “Milk has the highest viral load compared to any other body secretion.”
People who drink unprocessed milk should be vigilant, Lutz said.
“We do have raw milk consumption in our state,” she said. “There are multiple farms that have raw milk permits. We do not know if raw milk is safe to drink for humans.”
Farm workers who are exposed to unpasteurized milk in the milking process have some risk of contracting avian flu, Lutz said. She works to educate workers in Western New York about the illness and its prevention.
Routine testing at New York’s regional dairy processing plants has not detected avian influenza, but if a milk sample tested positive it could be immediately linked to the farm where it originated, said Capel, past president of the American Association of Bovine Practitioners. That’s because processors are required to test milk from incoming trucks, and they store a sample from each farm,” Capel said.
Nearly every state in the country has implemented the National Milk Testing Strategy which assures that milk is screened for the live H5N1 virus by farm or processor level, he said.
Milk testing is key because there is no vaccine licensed in the United States to prevent avian flu in cattle, Capel said.
Other avian flu precautions are taken when shipping cattle. Lutz said many dairy farms outsource the rearing of heifer calves to facilities in western states. Once grown, the heifers are returned to the farm of origin.
“Because we have transport of young stock across state lines, it’s something we have to be mindful of,” Lutz said.
New York requires young animals coming from out-of-state to receive a nasal swab test, Capel said, but flu risk among heifers is much smaller than among lactating cattle.
Capel advises farmers to ask for milk testing results on any individual cows they are considering purchasing.
“If I were purchasing from a farm, I would go to the farm and ask for milk testing for a couple of weeks.”
He said any new animals should be kept separately from the herd and monitored.
David McCollum, co-owner of McCollum Farms in Gasport with 1,500 dairy cows, joked that you can’t post a sign — Avian flu keep out.
“All you can do is keep things tightened up,” he said.
Infected cows recover with treatment, Capel said, but often do not resume full milk production. If they are culled, they can not be sold for human consumption.
Capel’s veterinary practice works with dairy farms on biosecurity plans to address avian flu and other disease risks.
“I think these individual plans are really critical,” he said. “Every farm is a little bit different, and risk factors on farms are a little bit different.” Grant funding has been available from the USDA to cover veterinarians’ consulting time, equipment, and protective gear.