Background: Understanding the epidemiology of human Mycobacterium bovis tuberculosis (TB) in the United States is imperative; this disease can be foodborne or airborne, and current US control strategies are focused on TB due to Mycobacterium tuberculosis and airborne transmission. The National TB Genotyping Service's work has allowed systematic identification of M. tuberculosis-complex isolates and enabled the first US-wide study of M. bovis TB.
Methods: Results of spacer oligonucleotide and mycobacterial interspersed repetitive units typing were linked to corresponding national surveillance data for TB cases reported for the period 2004-2005 and select cases for the period 1995-2003. We also used National TB Genotyping Service data to evaluate the traditional antituberculous drug resistance-based case definition of M. bovis TB.
Results: Isolates from 165 (1.4%) of 11,860 linked cases were identified as M. bovis. Patients who were not born in the United States, Hispanic patients, patients <15 years of age, patients reported to be HIV infected, and patients with extrapulmonary disease each had increased adjusted odds of having M. bovis versus M. tuberculosis TB. Most US-born, Hispanic patients with TB due to M. bovis (29 [90.6%] of 32) had extrapulmonary disease, and their overall median age was 9.5 years. The National TB Genotyping Service's data indicated that the pyrazinamide-based case definition's sensitivity was 82.5% (95% confidence interval; 75.3%-87.9%) and that data identified 14 errors in pyrazinamide-susceptibility testing or reporting.
Conclusions: The prevalence of extrapulmonary disease in the young, US-born Hispanic population suggests recent transmission of M. bovis, possibly related to foodborne exposure. Because of its significantly different epidemiologic profile, compared with that of M. tuberculosis TB, we recommend routine surveillance of M. bovis TB. Routine surveillance and an improved understanding of M. bovis TB transmission dynamics would help direct the development of additional control measures.