Tainted Cheese Fuels TB Rise in California

A rare form of tuberculosis caused by illegal, unpasteurized dairy products, including the popular queso fresco cheese, is rising among Hispanic immigrants in Southern California and raising fears about a resurgence of a strain all but eradicated in the U.S.

Cases of the Mycobacterium bovis strain of TB have increased in San Diego county, particularly among children who drink or eat dairy foods made from the milk of infected cattle, a study in the journal Emerging Infectious Diseases shows.

But the germ can infect anyone who eats contaminated fresh cheeses sold by street vendors, smuggled across the Mexican border or produced by families who try to make a living selling so-called “bathtub cheese” made in home tubs and backyard troughs.

Scientists at the University of California San Diego School of Medicine are warning that improved screening, treatment and public education are necessary to prevent the spread of the disease that now accounts for about 10 percent of all new cases of TB in that border region—and, perhaps, others.

“M. bovis TB is a disease of antiquity,” said Timothy Rodwell, a researcher who led the study published by the federal Centers for Disease Control and Prevention. “It is important that it not be allowed to re-emerge as a cause of TB in this country.”

Unlike typical TB, caused by the M. tuberculosis strain, the bovine variety isn’t easily spread through human-to-human contact. It settles less often in the lungs, making it less likely to be transmitted through breathing and coughing, Rodwell said.

Rare strain resists drug treatment

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Demand for Hispanic cheeses has skyrocketed in California, where 108 million pounds of legal, properly pasteurized queso fresco and other cheeses were produced last year, according to the California Department of Food and Agriculture.

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Officials seize illegal cheese

Agriculture officials have been cracking down on illegally produced cheese, including more than 375 pounds of so-called “bathtub cheese” seized from an open-air market in San Bernardino last year, according to Steve Lyle, the agency’s director of public affairs. Such cheeses have been found to be colonized with salmonella, listeria, E. coli and M. Bovis TB.

The problem stems from cattle in Mexico, where M. Bovis infects an estimated 17 percent of herds. In the U.S., the problem is limited to occasional outbreaks among isolated herds. Overall, the U.S. virtually eradicated the M. Bovis variety in the 1900s, Rodwell said.

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