High Prevalence of Toxoplasma gondii Infection in Miners: A Case-Control Study in Rural Durango, Mexico

BACKGROUND Very little is known about the seroepidemiology of infection with the parasite Toxoplasma gondii (T. gondii) in miners. We determine the association of T. gondii infection and the occupation of miner, and the association of seropositivity for T. gondii with the socio-demographic, clinical, work and behavioral characteristics of the miners. METHODS Through a case-control study, 125 miners working in Durango State, Mexico and 250 age- and gender-matched non-miner subjects were examined for the presence of anti-T. gondii IgG and IgM antibodies using enzyme-linked immunoassays. In addition, the presence of T. gondii DNA in miners was determined using polymerase chain reaction. Bivariate and multivariate analyses were used to determine the association of socio-demographic, work, clinical and behavioral characteristics of miners with T. gondii infection. RESULTS Anti-T. gondii IgG antibodies were detected in 75 (60.0%) of 125 miners and in 55 (22.0%) of 250 controls (odds ratio (OR) = 5.31; 95% confidence interval (CI): 3.33 - 8.47; P < 0.001). Among IgG seropositive subjects, the frequency of anti-T. gondii IgM antibodies was significantly higher in miners (39/75, 52%) than in controls (8/55, 14.5%) (P < 0.001). All T. gondii seropositive miners referred themselves as healthy. Multivariate analysis of socio-demographic, housing, and behavioral characteristics of miners showed that T. gondii seropositivity was positively associated with being born in Durango State (OR = 3.44; 95% CI: 1.09 - 10.7; P = 0.03), consumption of boar meat (OR = 5.53; 95% CI: 1.49 - 20.3; P = 0.01), living in an overcrowded home (OR = 5.83; 95% CI: 1.49 - 22.8; P = 0.01), and was negatively associated with cleaning cat excrement (OR = 0.33; 95% CI: 0.11 - 0.90; P = 0.03) and consuming goat meat (OR = 0.16; 95% CI: 0.03 - 0.76; P = 0.02). CONCLUSIONS Surprisingly, our results indicate that miners represent a risk group for T. gondii infection. This is the first age- and gender-matched case-control study on the association of T. gondii infection and the occupation of miner. Further studies to identify the exact cause of high seropositivity in miners in rural Durango are needed.