Potential contamination of drinking water with Toxoplasma gondii oocysts

The world's first documented toxoplasmosis outbreak associated with a munic ipal water supply was recognized in 1995 in Victoria, British Columbia, Can ada. It was hypothesized that domestic cat (Felis catus) or cougar (Felis c oncolor) faeces contaminated a surface water reservoir with Toxoplasma gond ii oocysts, An extensive investigation of the Victoria watershed 1 year fol lowing the outbreak documented the presence of an endemic T, gondii cycle i nvolving the animals inhabiting the area. Cats and cougars were observed th roughout the watershed. Serological evidence of T. gondii infection was dem onstrated among domestic cats living in the Victoria area. Cougars were fou nd to shed T, gondii oocysts. Serological evidence of T. gondii infection i n deer mice living in the riparian environments of the watershed suggested that T. gondii oocysts were being shed near the water edge. Contamination o f Victoria's water supply with T. gondii oocysts potentially occurred durin g the study period and future waterborne toxoplasmosis outbreaks in this an d other communities are possible.