489. Mycobacterium bovis: A Barrier to TB Elimination in California, 2003-2011
Session: Poster Abstract Session: Public Health
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Background:

Mycobacterium bovis, part of the Mycobacterium tuberculosis complex, is a zoonotic pathogen that can cause tuberculosis (TB) disease in humans. Nationally, M. bovis accounts for 1-2% of all human TB cases. M. bovis is associated with a high burden of pediatric cases, increased mortality, and HIV infection compared to M. tuberculosis.

Methods:

Culture-positive cases reported to the California TB registry from 2003-2011 were eligible for inclusion. Patients were classified as having M. bovis if drug susceptibility results showed resistance to pyrazinamide but susceptibility to isoniazid and rifampin. We conducted a retrospective review to evaluate trends and to identify differences between pediatric (< 15 years) and adult (≥ 15 years) M. bovis cases. Using surveillance variables introduced in 2010, odds ratios adjusted (aOR) for age, foreign-born status, race/ethnicity, sex, HIV-status, and site of disease and 95% confidence intervals (95% CI) were calculated to assess factors associated with  M. bovis risk compared to M. tuberculosis.

Results:

The proportion of M. bovis cases increased from 3.4% (80/2384) in 2003 to 5.4% (98/1800) in 2011 (p=0.002). In bivariate analysis, compared to pediatric cases, adult cases were more likely to have pulmonary disease (62% vs 13%, p<0.001, respectively) and be foreign-born (83% vs 15%, p<0.001, respectively) and less likely to be Hispanic (79% vs 99%, p<0.001, respectively). From 2010-2011, most pediatric M. bovis cases were US-born (4/6, 66%) but all had at least one parent/guardian born in Mexico. Diabetes mellitus (aOR=1.6, 95% CI: 1.1-2.3) and co-morbid immunosuppressive conditions other than HIV (e.g., post-organ transplantation, end-stage renal disease, TNF-α antagonist therapy) (aOR=1.7, 95% CI: 1.1-2.7) were independently associated with M. bovis.

Conclusion:

California has a higher M. bovis burden than the national average and the number and fraction of cases are not declining. To promote TB elimination, M. bovis prevention efforts should focus on binational families and the immunocompromised. Understanding source and route of transmission and whether infection was recent or remote can assist future prevention strategies.

Mark Gallivan and Jennifer Flood, MD, MPH, California Department of Public Health, Tuberculosis Control Branch, Richmond, CA

Disclosures:

M. Gallivan, None

J. Flood, None

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