Prevalence and Factors Associated with Mycobacterium tuberculosis Transmission in Domestic Elephants and Human Contacts, Thailand, 2012

Abstract

We conducted a study in an elephant village in Surin Province to assess the prevalence of TB in elephant keepers and their family members, to identify factors associated with TB infection and to recommend strategies for prevention and control of disease transmission between humans and animals. The study methods included (1) a survey using structured questionnaire to interview mahouts to collect data on history of illness and routine activities with their elephants; (2) a laboratory-screening for TB included tuberculin skin test (TST) and chest radiography CXR). during 1 October – 2 November 2012. A laboratory-confirmed case was identified by sputum smear positive AFB and culture positive for M. tuberculosis. This study used data on trunk-wash culture and serum antibody tests (Elephant TB STAT-PAK kit) for TB in elephants which were conducted by Thailand Zoological Park Organization. It was found that among 291 elephant keepers surveyed, 160 (60.2%) were positive reaction or TST e” 10 mm. We found 89 (30.6%) had abnormal CXR and 26 (8.9%) met a suspected TB case definition, 3/19 (15.8%) few AFB-smear positive (only 1 cell) but no confirmed TB case by culture-positive sputum. In crude and adjusted analysis, risk behaviors of mycobacterium infection between elephant keepers and their elephants were not associated with detected TB disease. Of 190 elephants surveyed, 38 (20.0%) showed evidence of mycobacterium infection by rapid serological screening (STAT-PAK), no laboratory confirmation for TB by trunk-wash culture. Three infected captive elephants died with undiagnosed cause after autopsy; therefore TB as a cause of death could not be ruled out. Four clusters of TB-positive elephants were observed and the elephants lived together in close proximity. In conclusion, high percentage of TST of M. tuberculosis infections was detected among people who were in close contact with elephants. No significant associations between studied factors and TB disease in the elephant keepers. Mycobacterium-infected elephants living closely with other elephants might increase risk of TB transmission. Development of TB surveillance in the Elephant Village and proper management of TB in elephants and associated humans was recommended.