2010 Annual Report 1a.Objectives (from AD-416) To develop methods to detect and disinfect Toxoplasma gondii oocysts in water. 1b.Approach (from AD-416) Sporulated oocysts will be mixed with different disinfectants and then bioassayed in mice for infectivity. 3.Progress Report Toxoplasma gondii oocysts are highly resistant to many chemical sanitizers. In the present study, methods were evaluated to measure the effect of treating oocysts with ultraviolet rays and chemical sanitizers by using PCR, animal bioassays, and in vitro cultivation in cell cultures. The PCR assay was most sensitive but it could not distinguish between live and dead oocysts. The sensitivity of the cell culture method was similar to the animal bioassays. None of the chemicals, including Clorox and iodine, and ultraviolet rays commercially used in water treatment plants were effective in killing Toxoplasma oocysts. Project plans, goals, and accomplishments were discussed via conference calls and e-mail; technical advice was provided to the Cooperator in writing and by teleconference.