Rare, Drug Resistant Tuberculosis Linked to Queso Fresco CheeseJun 6, 2008 | Parker Waichman LLP A rare form of tuberculosis—Mycobacterium bovis—has emerged and been traced to illegal, unpasteurized dairy products, including tainted queso fresco cheese. The outbreak is rising among Hispanic immigrants in Southern California and is also raising fears about a revival of this strain that was nearly completely destroyed in the US in the 1900s.
The increase in this TB is being seen chiefly in San Diego, particularly among children who drink or eat dairy foods made from the milk of infected cattle, but Mycobacterium bovis TB can infect anyone who eats contaminated fresh cheeses sold by street vendors, smuggled across the Mexican border, or produced as so-called “bathtub cheese” made in home tubs and backyard troughs. The problem originates from cattle in Mexico, where M. Bovis infects about 17 percent of herds; occasional outbreaks among isolated herds affect the US.
This rare TB accounts for about 10 percent of all new TB cases in the California border region. “M. bovis TB is a disease of antiquity,” said Timothy Rodwell, a researcher who led a study published by the federal Centers for Disease Control and Prevention (CDC). “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, this reemerging bovine variety does not easily spread via human-to-human contact and tends to land less often in the lungs, making it less likely to be transmitted through breathing and coughing, Rodwell said. Unfortunately, this rare strain resists drug treatment and is resistant to front-line drug therapy. Adults who contract M. bovis TB are more than twice as likely as those with traditional TB to die before completing treatment.
Researchers analyzed nearly 3,300 culture-confirmed cases of TB in San Diego between 1994-2005. Approximately 265 were identified as M. bovis, this increased by nearly 65 percent, rising from 17 to 28 cases annually. By 2005, over half the M. bovis cases were diagnosed in children under 15. The majority were in Hispanics; 60 percent from Mexico. Between 2001-2005, 19 adults with M. Bovis died before or during treatment. Dr. Kathleen Moser, director of TB control programs for San Diego County said, “It’s clearly being seen and being seen in places where people drink unpasteurized milk and eat unpasteurized dairy products.”
In California, 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. Last year, Moser launched a public health campaign and agriculture officials seized over 375 pounds of “bathtub cheese” from an open-air market in San Bernardino, according to Steve Lyle, the agency’s director of public affairs. Such illegal cheeses have been infected with Salmonella, Listeria, E. coli, and M. Bovis TB.
Rodwell cautioned that people worried about M. bovis strain TB should pay close attention to dairy products, not people. “It is NOT a disease you are very likely to get from a foreign-born person,” he said. “The increase in M. bovis cases is more about what you eat, not where you were born.”