Epidemiology and Infection

Potential contamination of drinking water with Toxoplasma gondii oocysts

a1 Department of Herd Medicine and Theriogenology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
a2 Centre for Coastal Health, Malaspina University-College, Nanaimo, British Columbia, Canada
a3 Parasite Biology and Epidemiology Laboratory, Livestock and Poultry Sciences Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland, USA
a4 Alula Biological Consulting, Saanichton, British Columbia, Canada
a5 Wildlife Branch, Ministry of Environment Lands and Parks, British Columbia, Canada


The world's first documented toxoplasmosis outbreak associated with a municipal water supply was recognized in 1995 in Victoria, British Columbia, Canada. It was hypothesized that domestic cat (Felis catus) or cougar (Felis concolor) faeces contaminated a surface water reservoir with Toxoplasma gondii oocysts. An extensive investigation of the Victoria watershed 1 year following the outbreak documented the presence of an endemic T. gondii cycle involving the animals inhabiting the area. Cats and cougars were observed throughout the watershed. Serological evidence of T. gondii infection was demonstrated among domestic cats living in the Victoria area. Cougars were found to shed T. gondii oocysts. Serological evidence of T. gondii infection in deer mice living in the riparian environments of the watershed suggested that T. gondii oocysts were being shed near the water edge. Contamination of Victoria's water supply with T. gondii oocysts potentially occurred during the study period and future waterborne toxoplasmosis outbreaks in this and other communities are possible.

(Accepted November 12 1998)

c1 Author for correspondence: J. J. Aramini, Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada, N1G 2W1.