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Investigation Underway for Bovine Tuberculosis Case in CA

Agriculture officials in California are currently investigating cases of bovine tuberculosis in a dairy cow herd first reported last Wednesday.

The bacteria that causes bovine tuberculosis (TB) can spread to humans via raw milk, but the cow belonged to a dairy in Tulare County which pasteurizes all of its milk, thus eliminating the risk of tuberculosis transmission.

The problem was originally detected at a slaughter yard where a cow from the dairy had been sent. Routine slaughter testing found TB in that cow, and follow-up testing by the California Department of Food and Agriculture (CFAD) found the presence of TB among the cow’s dairy herd.

While state veterinarians perform genetic sub-typing of that herd’s infections, they are also conducting a traceback investigation on the cows at the slaughter yard with which the infected dairy cow might have been in contact, a CFAD spokesman told Food Safety News.

In an email to associates in veterinary science and epidemiology, California State Veterinarian Annette Jones said that this most recent case was most likely not associated with multiple cases of bovine TB discovered in San Bernardino County dairy cows throughout 2011.

“We are just beginning to look into how this TB case was introduced and if it has spread — testing for TB is a long and arduous task with less than perfect tests at our disposal,” Jones wrote, “so it may be weeks to months before we have additional information to share.”

“While our staffing has been significantly reduced,” the email continued, “we will make understanding, containing and eradicating TB our number one priority and hope that we can limit the number of impacted herds as quickly as possible.”

Though no raw-milk dairy cows are believed to be infected with TB, the CFAD has reminded consumers that the state requires regular TB tests at raw milk dairies.

Cattle are inspected for signs of TB at the time of slaughter and removed from processing if they exhibit any signs.

In April 2011, eight cows at a San Bernardino County dairy were found infected with TB after a herd member tested positive at slaughter for a strain previously unseen in the U.S. Later that year, another 66 cows in the county were found infected with a different TB strain.

A total of 8 TB-infected cows were detected in California between 2003 and 2009. The state had first gained its bovine “TB-Free” status in 1999, and was on a timeline to regain the status until the 2011 infections.

In January, a dairy cow in Washington state tested positive for bovine TB, the first case in the state since 1988.

The U.S. government established the first federal TB eradication program in 1917.

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