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Incidence of M. bovis TB grows in California
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The incidence of human Mycobacterium bovis disease in California has not decreased, and the proportion of tuberculosis cases resulting from M. bovis has increased further beyond the U.S. average, according to recent findings.
In a retrospective review, researchers evaluated data on 18,752 patients with culture-confirmed TB who were enrolled in the California TB registry between 2003 and 2011. Patients identified for inclusion had initial drug susceptibility testing results for isoniazid, rifampin, and pyrazinamide.
M. bovis disease was classified in patients whose initial drug susceptibility results demonstrated resistance to pyrazinamide and susceptibility to isoniazid and rifampin. The researchers reviewed the registry for sociodemographic, clinical and treatment outcome information for all case-patients. They conducted bivariate analysis with variables that were added to the national TB surveillance system in 2010 to assess factors associated with TB disease caused by M. bovis vs. TB disease caused by M. tuberculosis. The researchers also assessed epidemiologic disparities between adult and child case-patients with M. bovis disease.
The proportion of TB cases in California for all ages caused by M. bovis grew from 3.4% of 2,384 cases in 2003 to 5.4% of 1,808 cases in 2011 (P = .002). By comparison, researchers said 1% to 2% of TB cases in the U.S. are attributable to M. bovis infection. All six cases of M. bovis disease in children during 2010-2011 had at least one parent or guardian who was born in Mexico vs. 38% of child case-patients with disease attributable to M. tuberculosis (P = .005). In multivariate analysis, the researchers determined the following factors were independently associated with M. bovis disease: Hispanic ethnicity, extrapulmonary disease, diabetes and immunosuppressive conditions compared with M. tuberculosis.
According to the researchers, California has implemented measures to prevent M. bovis disease.
“In California, there are ongoing interventions designed to limit the demand for and distribution of unpasteurized and contaminated dairy products, which are associated with M. bovis disease and other foodborne diseases,” the researchers wrote. “Elimination of human M. bovis disease in California likely requires further implementation of programs to reduce M. bovis contamination.”
Disclosure: The researchers report no relevant financial disclosures.
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