A third human case of highly pathogenic avian influenza (HPAI) A(H5) virus infection related to dairy cattle was reported by the Centers for Disease Control and Prevention last Thursday, May 30. This person is from Michigan and works on a farm where cows had tested positive for HPAI. The two previous cases, one in Texas and another in Michigan, also involved workers on dairies where cows were sick with the virus.

There have only been four human cases of avian influenza reported in the United States. The first occurred in 2022 in a person in Colorado who had direct exposure to poultry being depopulated during the outbreak in birds. General symptoms of avian influenza in humans include fever, cough, muscle aches, general fatigue, sore throat, nausea or vomiting, and shortness of breath.

The current risk to the general public remains low; people at greatest risk for contracting HPAI appear to be those who have direct contact with infected animals. This includes milkers or other workers in direct contact with unpasteurized milk from infected cows. That’s because USDA analysis from nasal swabs, tissue, and milk samples showed that the highest concentration of virus shedding is found in milk prior to pasteurization, and virus replication in the dairy cow occurs mainly in the udder.

In a Michigan State University Extension article, dairy extension educator Martin Carrasquillo-Mangual explained that exposure could happen during forestripping, milk testing, or from cows leaking milk. Milk can also be found on equipment, used towels, work clothes, the parlor floor, and more, elevating the risk for contact. People feeding raw milk to calves can also be exposed.

“However, many of these processes are vital for the optimal functioning of a dairy farm,” Carrasquillo-Mangual recognized. “This highlights the importance of increasing awareness and implementing strategies to reduce the risk to dairy farm workers.”

Protection starts with thorough handwashing before and after working with cows. After a milking shift, Carrasquillo-Mangual recommended showering or at least washing the hands and face with water and soap.

A good line of defense is the use of personal protective equipment. He said gloves should be worn at all times in the parlor and replaced if torn. This includes cow pushers who step into the milking pit, he added.

Clothes worn during milking should be washed after each shift or at least kept separate from other clothing. Boots should be cleaned before a milking shift and cleaned and disinfected afterwards. Carrasquillo-Mangual encouraged farm owners to provide a container with chlorinated water nearby so milkers can step in it to clean their boots every time they leave the milking area. “It is important to rinse the boots to remove manure and sand prior to disinfection,” Carrasquillo-Mangual noted.

If a herd is confirmed positive, further steps can be taken to avoid exposure, such as wearing safety glasses to protect eyes from milk splashes, not touching the face, eyes, and nose when working, and disposing gloves when leaving the milking area. “Any equipment that protects the worker from milk droplets can aid in reducing the risk of infection,” Carrasquillo-Mangual said.

If HPAI is detected on the premise, Carrasquillo-Mangual advised against feeding raw milk to cats or other animals, as this can lead to further spreading of the disease.

“Although current information suggests that HPAI presents a low risk to humans and those affected have recovered successfully without any major setback, we should still employ methods to reduce the risk of infection and limit the spread of this disease,” Carrasquillo-Mangual concluded. “HPAI still presents clinical symptoms in humans that may vary in severity and length. Therefore, any action to mitigate the risk of infection will lead to a safer work environment.”

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June 6, 2024
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