Mycobacterium bovis as a significant cause of tuberculosis in children residing along the United States-Mexico border in the Baja California region

Objective. To determine the role of Mycobacterium bovis in active pediatric tuberculosis (TB) in a United States-Mexico border region. Method. We reviewed all new cases of pediatric (<15 years old) TB presenting to San Diego hospitals and clinics from 1980 to 1997. Patients were categorized by age, ethnicity, country of origin, culture results, and disease manifestations. Case definitions were similar to those used by the Centers for Disease Control and Prevention. M bovis was distinguished from Mycobacterium tuberculosis by standard biochemical tests. Results. The median age of the 563 identified patients was 4.1 years old. The yearly incidence began rising in 1989 and peaked in the mid-1990s. Hispanics constituted 78.9% of the patients, but they were less likely to be foreign-born (21.6%) than were black children and Asian/Pacific Islanders. Overall, M bovis caused 10.8% of all TB during this period. Of the 180 patients with positive culture results, however, M bovis accounted for 33.9% and M tuberculosis 66.1%. This high percentage of M bovis infections was largely attributable to its contribution to extrapulmonary TB (55.2% of all culture-positive specimens). M bovis patients were also even more likely to be Hispanic (90.2%), to present with extrapulmonary disease (95.1%), and to be older than 12 months (96.8%). Conclusion. These data demonstrate the dramatic impact of this underappreciated cause of zoonotic TB on US children at the Mexican border and underscore the need for cross-collaboration to enforce existing Mexican pasteurization laws.