Trending
UNIVERSITY PARK -- With nine states to date reporting dairy herds affected by a syndrome thought to be caused by a highly pathogenic strain of avian influenza, animal health experts and extension educators in Penn State’s College of Agricultural Sciences have mobilized to provide dairy producers with information that can help protect their herds from infection.
The rapidly evolving situation began in March, when the U.S. Department of Agriculture confirmed that dairy cows in Texas and Kansas were infected with highly pathogenic avian influenza, or HPAI. Although the virus is generally not fatal to cattle -- as it is in poultry -- affected animals have exhibited a drop in feed intake and milk production, thickened abnormal milk, and often dry, tacky manure, among other symptoms.
Since the initial incidents in Texas and Kansas, USDA has confirmed other HPAI infections in dairy cattle in Michigan, New Mexico, Idaho, Ohio, North Carolina, South Dakota and Colorado. The H5N1 strain found in the cows is the same virus that since 2022 has caused outbreaks in poultry across the country, including in Pennsylvania, which so far has not reported any infected cattle.
Wild birds -- and especially waterfowl -- which are natural carriers of HPAI, are believed to be the original source of infections in cattle, according to USDA. But Hayley Springer, extension veterinarian in Penn State’s College of Agricultural Sciences, noted that the latest information indicates that the virus likely spreads from cow to cow.
“How the virus is spreading is not yet well understood, but there’s clear evidence of cow-to-cow transfer,” said Springer, who is also an associate clinical professor in the college’s Department of Veterinary and Biomedical Sciences. “I don’t think we can rule out bird introductions, but I think that’s going to be less likely, at least in Pennsylvania, than cow-to-cow transmission.”
Extension veterinarian and clinical professor Ernest Hovingh, who directs Penn State’s Animal Diagnostic Laboratory, pointed out that some infections have been associated with the movement of cattle from an affected herd to a herd in another state.
“The epidemiological evidence suggests that we don’t have the same birds shedding the virus in Michigan as in South Dakota, as in North Carolina, as in Texas and Kansas,” he said. “The movement of cattle is strong evidence that there’s animal transmission occurring. Some of that might be fomites (objects or materials that can be contaminated with a pathogen), such as contaminated milk from a cow coming in contact with another cow, since milk from infected cows tends to have high levels of virus. We don’t know the exact mechanism, but it certainly looks like there’s virus being transferred from one cow to another by some means.”
Springer and Hovingh emphasized that the possibility of cows shedding virus in their milk does not represent a food-safety issue.
“Milk from cows that are known to be sick is diverted from the milk supply, in accordance with Food and Drug Administration regulations,” Hovingh said. “But even if viral or bacterial pathogens are present, milk sold for processing or retail sale in interstate commerce must be pasteurized by law, and pasteurization was developed to inactivate any harmful organisms.”
This point was confirmed by the FDA, which announced that, although HPAI virus fragments have been found in pasteurized milk, these findings “do not represent actual virus that may be a risk to consumers.” The agency added that “to date, we have seen nothing that would change our assessment that the commercial milk supply is safe.”
Hovingh said that the Animal Diagnostic Lab at Penn State, one of three facilities in the state-funded Pennsylvania Animal Diagnostic Laboratory System, is prepared to test milk and swabs from cows that are suspected of being infected with the virus. In response to a recently-issued federal order that requires testing of lactating cows before they can move across state lines, the lab also is prepared for “pre-movement testing” of milk samples.
Despite HPAI showing up recently in livestock and other mammals, federal authorities said that they have found no evidence that the virus has evolved to make it more transmissible to humans and between people. And while one case of human infection appears to have occurred in Texas in a farm worker who was in direct contact with infected cattle, they believe that the current risk to the public remains low. Regardless, Springer said she recommends that people working with dairy cows on infected farms take precautions.
“If you have a herd that tests positive, since there is a good bit of virus in the milk, the Centers for Disease Control recommends eye protection, masks and gloves, among other protections for those in direct contact with cattle,” she said. “Having personal protective equipment on hand can assure a farm is prepared should they suspect the disease.”
Penn State Extension has offered webinars and workshops to provide dairy producers with the latest information and to help them craft biosecurity plans. Following are some recommendations from Penn State experts for protecting cattle from HPAI:
-- Avoid bringing new animals onto the farm, especially lactating animals.
-- Limit visitors to those essential to the farm, and exclude visitors from animal areas when possible. Provide visitors with boot covers or access to farm-dedicated boots.
-- Do not share equipment that will enter animal housing areas between farms. Thoroughly clean and disinfect equipment if moved between premises.
-- Work with your herd veterinarian to develop a biosecurity plan, including pre-movement testing for any animals that must be brought onto the farm.
-- Restrict farm vehicle access to areas contaminated with waterfowl feces.
-- Identify areas where birds congregate in buildings and install barriers or deterrents to limit access to these areas.
-- Fence cattle away from ponds or other areas where waterfowl frequent.
-- Avoid using untreated surface water for cattle drinking water.
-- Fully empty and disinfect water troughs frequented by birds.
Hovingh and Springer pointed out that the Pennsylvania Department of Agriculture has placed testing requirements on the movement of cattle from herds in affected states into Pennsylvania, and the department will require a farm that has an HPAI-positive herd to have an approved biosecurity plan and to obtain a permit to move milk from the farm to a facility for pasteurized processing. The recent federal order now also will require testing of lactating cattle that move into the commonwealth from uninfected states.