Submitted to: Journal of Infectious Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/1/2010
Publication Date: 10/10/2010
Citation: Vaudaux, J.D., Muccioli, C., James, E.R., Silveira, C., Jung, C., Dubey, J.P., Jones, J.L., Doymaz, D.A., Bruckner, D.A., Belfort, R., Holland, G.N., Grigg, M.E. 2010. Identification of an atypical strain of Toxoplasma gondii as the cause of a waterborne outbreak of toxoplasmosis in Santa IsabeldoIvai, Brazil. Journal of Infectious Diseases. 202:1226-1233. Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. This paper reports details of an outbreak of toxoplasmosis in humans linked to water contamination. The results will be of interest to biologists, parasitologists, public health workers, and veterinarians.
Technical Abstract: We have identified an atypical strain of Toxoplasmagondii as the causative agent of the 2001 outbreak of toxoplasmosis in Santa Isabel do Ivai, Brazil, which resulted in approximately 426 human infections. The epidemic clone was isolated from multiple water filters collected from a cistern linked epidemiologically to the outbreak. When passaged through mice, it was highly virulent. Multilocus DNA sequencing showed that the strain possessed a non-archetypal genotype previously identified in Brazil (designated BrI). To identify people infected with the outbreak clone, 20 IgM-positive individuals were screened using a serologic assay that detects strain-specific antibodies. The serotype identified in infected mice was present in the majority of individuals infected during the outbreak (13; 65%), confirming the purported agent as the epidemic strain. The remaining seven people, plus additional IgM-negative, IgG-positive individuals possessed one of four novel serologic profiles, the most common of which matched the serotype from mice infected with strains isolated from chickens grazing nearby the outbreak. These latter strains likely reflect the substantial genetic diversity of T. gondii strains circulating in regions of Brazil with highly endemic disease. The serotyping assay proved to be a useful tool for specific identification of individuals infected with the outbreak agent.