TULARE COUNTY – One-hundred dairies in the Central Valley have cattle infected with Bird Flu, according to a recent update by state and federal agriculture agencies.
The Oct. 11 alert issued by the California Department of Food and Agriculture (CDFA) reported the alarming number of H5N1 Avian Flu infections following a joint investigation with California Animal Health and Food Safety Laboratory System (CAHFS), the U.S. Department of Agriculture’s (USDA) National Veterinary Services Laboratories (NVSL).
“CDFA has implemented a surveillance strategy with the goal of finding affected farms as early as possible,” the alert stated. “Early detection provides the opportunity to work with farms to quickly implement enhanced biosecurity, cow care, and employee protection.”
The California Department of Public Health (CDPH) has confirmed six human cases of bird flu in California. All individuals had contact with animals at different farms and all have experienced mild symptoms, including eye redness or discharge (conjunctivitis). None of the individuals have been hospitalized.
“While the risk to the general public remains low, additional human cases of bird flu are expected to be identified and confirmed in California among individuals who have contact with infected dairy cattle,” the alert stated.
CDFA also reminded consumers there is no safety concern with milk from infected cows. Pasteurization of milk kills the virus, making pasteurized milk and dairy items safe to eat. Dairies must also remove sick cows from the group that produces milk for the food supply. It is standard practice to move these animals to the part of the dairy set up for recovery.
The virus is primarily transmitted through movement of infected livestock. Transmission between farms is likely due to normal business operations including the movement of animals, contaminated vehicles and other farm equipment frequently moving on and off affected premises and on to other premises, according to CDFA. Additionally, H5N1 avian influenza infected cattle can have an asymptomatic incubation period of about 3-10 days so, when infected cattle that look healthy are moved, noninfected cattle are exposed to the virus.
Cattle infected with Bird Flu may show symptoms including:
- Decrease in feed consumption with a simultaneous decrease in rumination and rumen motility
- Respiratory signs including clear nasal discharge
- Acute drop in milk production. Severely affected cattle may have thicker, concentrated, colostrum-like milk or produce no milk at all.
- Abnormal tacky or loose feces
- Lethargy
- Dehydration
- Fever
CDPH is recommending that anyone working with animals potentially infected with Bird Flu to use personal protective equipment (PPE), such as eye protection (face shields or safety goggles), respirators (N95 masks) and gloves.
The report did not identify the location of any of the dairies, but it appears all six of the human cases were from Tulare County, where three have been confirmed. Tulare is also the largest dairy county in the nation, with more cows than people.
“Although there is an additional confirmed human case of bird flu, this is to be expected with current outbreaks at dairy cattle facilities,” stated Dr. Thomas Overton, Deputy County Health Officer for Tulare County Public Health.
While the risk to the general public remains low, additional human cases of bird flu are expected to be identified and confirmed in California among individuals who have contact with infected dairy cattle.
The outbreak can be traced back to a single incident of Bird Flu that infected a dairy cow in Texas. According to CDFA, that led to the current outbreak of Bovine Influenza A across the U.S. On Aug. 30, 2024, California dairies located in the Central Valley tested positive for the virus. All affected dairies are placed under quarantine and enhanced biosecurity measures are in place to prevent the spread of the virus. Sick cows are isolated and are being treated at the dairies. Most infected livestock and dairy cattle can fully recover from H5N1 infection within a few weeks but often don’t recover their pre-infection milk production.
