Torres-Gonzalez P, Soberanis-Ramos O, Martinez-Gamboa A, Chavez-Mazari B, Barrios-Herrera MT, Torres-Rojas M, Cruz-Hervert LP, Garcia-Garcia L, Singh M, Gonzalez-Aguirre A, Ponce de Leon-Garduño A, Sifuentes-Osornio J, Bobadilla-del-Valle M. Prevalence of latent and active tuberculosis among dairy farm workers exposed to cattle infected by Mycobacterium bovis.
PLoS Negl Trop Dis 2013;
7:e2177. [PMID:
23638198 PMCID:
PMC3636137 DOI:
10.1371/journal.pntd.0002177]
[Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 03/10/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND
Human tuberculosis caused by M. bovis is a zoonosis presently considered sporadic in developed countries, but remains a poorly studied problem in low and middle resource countries. The disease in humans is mainly attributed to unpasteurized dairy products consumption. However, transmission due to exposure of humans to infected animals has been also recognized. The prevalence of tuberculosis infection and associated risk factors have been insufficiently characterized among dairy farm workers (DFW) exposed in settings with poor control of bovine tuberculosis.
METHODOLOGY/PRINCIPAL FINDINGS
Tuberculin skin test (TST) and Interferon-gamma release assay (IGRA) were administered to 311 dairy farm and abattoir workers and their household contacts linked to a dairy production and livestock facility in Mexico. Sputa of individuals with respiratory symptoms and samples from routine cattle necropsies were cultured for M. bovis and resulting spoligotypes were compared. The overall prevalence of latent tuberculosis infection (LTBI) was 76.2% (95% CI, 71.4-80.9%) by TST and 58.5% (95% CI, 53.0-64.0%) by IGRA. Occupational exposure was associated to TST (OR 2.72; 95% CI, 1.31-5.64) and IGRA (OR 2.38; 95% CI, 1.31-4.30) adjusting for relevant variables. Two subjects were diagnosed with pulmonary tuberculosis, both caused by M. bovis. In one case, the spoligotype was identical to a strain isolated from bovines.
CONCLUSIONS
We documented a high prevalence of latent and pulmonary TB among workers exposed to cattle infected with M. bovis, and increased risk among those occupationally exposed in non-ventilated spaces. Interspecies transmission is frequent and represents an occupational hazard in this setting.
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