Determining UV Inactivation of Toxoplasma gondii Oocysts by Using Cell Culture and a Mouse Bioassay

The effect of UV exposure on Toxoplasma gondii oocysts has not been completely defined for use in water disinfection. This study evaluated UV-irradiated oocysts by three assays: a SCID mouse bioassay, an in vitro T. gondii oocyst plaque (TOP) assay, and a quantitative reverse transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1- and 3-log₁₀ inactivation is achieved with 4 mJ/cm² UV and 10 mJ/cm² low-pressure UV, respectively. TOP assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3-log₁₀ inactivation of T. gondii oocysts is achieved by 10-mJ/cm² low-pressure UV, and the in vitro TOP assay is a promising alternative to the mouse bioassay.