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

Background: Very little is known about the seroepidemiology of infection with the parasite in miners. We determine the association of infection and the occupation of miner, and the association of seropositivity for 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- IgG and IgM antibodies using enzyme-linked immunoassays. In addition, the presence of 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 infection.

Results: Anti- 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- IgM antibodies was significantly higher in miners (39/75, 52%) than in controls (8/55, 14.5%) (P < 0.001). All seropositive miners referred themselves as healthy. Multivariate analysis of socio-demographic, housing, and behavioral characteristics of miners showed that 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 infection. This is the first age- and gender-matched case-control study on the association of infection and the occupation of miner. Further studies to identify the exact cause of high seropositivity in miners in rural Durango are needed.