We found comparable seroprevalences of both anti-T. gondii IgG and IgM antibodies, and comparable frequencies of anti-T. gondii IgG levels higher than 150 IU/ml in patients suffering from a recent work accident and controls. However, a subset of workers with work accidents and low socioeconomic level showed a significantly higher seroprevalence of T. gondii infection than control subjects of the same socioeconomic level. These results suggest that in general, T. gondii infection seems not be associated with work accidents in the population of Mexican workers from Durango; but in particular, suggest that T. gondii infection might be a contributing factor for work accidents in workers with low socioeconomic status. In principle, T. gondii may affect senses important to avoid any kind of accidents namely vision and hearing. It is well known that infections with T. gondii may lead to chorioretinitis [1, 2] thus affecting vision. Furthermore, infection with T. gondii has been linked to deafness  or hearing impairment . Seroprevalence of T. gondii has been found higher in individuals with reflex [9, 10, 15] and memory  impairments than those without these impairments. In the present study, we did not find an association of T. gondii infection with a specific impairment in patients with work accidents. This fact might explain the lack of association between T. gondii infection and work accidents in general.
Of the socio-demographic characteristics, a low socio-economic status was associated with T. gondii infection in our patients. This result confirms that of a previous report in our region . A low socioeconomic level may be linked to malnutrition, and this factor might impair the host defense against T. gondii infection. Therefore, it is likely that health could be more easily impacted by T. gondii in workers with low socioeconomic status than in workers with higher socioeconomic status. This is supported by the fact that health in Tepehuanos, one of the poorest populations in Durango, has been impacted by T. gondii infection. In a recent study in Tepehuanos, seropositivity to T. gondii was associated with frequent headaches and hearing impairment . In addition, other factors might contribute to an increase in the likelihood of an accident in T. gondii seropositive subjects. Several reports indicate that T. gondii infection may affect the reaction time in infected individuals. Havlícek et al.  in a double blind study showed significantly longer reaction times of subjects with latent toxoplasmosis in comparison with those of controls. Moreover, those researchers found a positive correlation between length of infection and mean reaction time suggesting that slow and cumulative effects of latent toxoplasmosis rather than a one-step (and possible transient) effect of acute toxoplasmosis disease are responsible for the decrease of psychomotor performance of infected subjects. Novotná et al.  showed that heterozygous men with both the RhD plus and the RhD minus alleles were protected against prolongation of reaction times caused by infection with T. gondii. In a further study in men and women, Flegr et al.  confirmed that RhD-positive subjects were less sensitive to the influence of latent toxoplasmosis on reaction times than RhD-negative subjects. In the present study, Rh blood typing in patients and controls was not determined.
Behavioral/mental disorders in humans including schizophrenia, mood disorders, personality changes, and cognitive impairments may be related to infection with T. gondii [12, 21, 22]. In addition, experimental infection with T. gondii in rodents has caused changes in behavior including a loss in aversion to cat odor . Behavioral/mental changes induced by T. gondii might impair the work performance leading to work accidents.
With respect to behavioral characteristics, multivariate analysis showed a positive association of T. gondii infection with consumption of boar meat. Remarkably, in a previous independent study, we also found and association of boar meat consumption with T. gondii infection .
Our study has limitations. First, the sample size and power may not have been large enough to determine all risk factors and associations. Second, the type of accidents could be not severe enough to find further associations. The general population in Durango has shown low seroprevalence of T. gondii infection [23, 24] as compared with those in other Mexican states . A low seroprevalence in Durango has been found even when using various kits detecting anti-T. gondii IgG antibodies. For instance, Velasco-Castrejón et al.  reported a 9.6% seroprevalence in population of Durango by an indirect immunofluorescence antibody test. Similarly, a 6.1% seroprevalence was found in pregnant women who attended a public hospital of Durango City by a microparticle enzyme immunoassay . Therefore, the seroprevalences found in the present study by enzyme-linked immunosorbent assay seem to be reliable. It is likely that the dry climate and high altitude in Durango may partially explain the low prevalence in Durango. Infection with T. gondii is more prevalent in low-lying areas than in mountainous areas and in humid areas than in dry areas .