Objective: To examine the relationship between antibody status and various hypothesized risk factors for Toxoplasma gondii infection among two different Amerindian populations in eastern Panama. Following up on earlier research that we conducted, we now explore the role of dogs in the natural transmission of Toxoplasma, the role that dogs play in promoting transmission, the interactive effect of cats and dogs, and the accessibility of infective material to children.
Methods: In 1991, 10 Panamanian medical students conducted interviews and took blood samples from 760 Kuna and Embera children aged 2 through 12 years in the Upper Bayano River Basin and the San Blas Islands. Serologic assays were performed using direct agglutination. The data analyses in the 1990s included univariate, bivariate, and multivariate analyses, without regard to data on dogs. Further bivariate and multivariate analyses were performed in 2003 to examine the contribution of dogs.
Results: In communities with high Toxoplasma antibody prevalence in children, logistic regression suggested that the factors predictive of antibody presence were: compacted soil floors of huts (P = 0.001), having a dog (P = 0.038), and the interviewer seeing a cat in the house (P = 0.049). Our results suggest that the villagers' dogs play a significant role in facilitating the transmission of Toxoplasma gondii to humans, most often in the presence of cats in the houses, and only in those communities with higher Toxoplasma seroprevalence in children.
Conclusions: Dogs may act as mechanical vectors, by rolling in foul-smelling substances and by ingesting fecal material. In areas of high Toxoplasma prevalence in children and where dogs and cats are plentiful, immunocompromised individuals and pregnant women should be warned of the possibility of acquiring Toxoplasma gondii from dogs as well as from soil contaminated by cats. People should be encouraged to wash their hands after contact with soil, dogs, or cats as well as before eating.