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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Gamma Irradiation on Unsporulated and Sporulated Toxoplasma Gondii Oocyst

Authors
item Dubey, Jitender
item Thayer, D - NAA, WYNDMOOR, PA
item Speer, C - MONTANA STATE UN, MONTANA
item Shen, Samuel

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 1998
Publication Date: N/A
Full Text Available

Interpretive Summary: Coccidia are a group of protozoan (singled celled) parasites that cause disease in humans and animals. A resistant stage of these parasites (oocysts) can contaminate fruits, vegetables, and other food products. Humans can become infected by ingesting food contaminated with oocysts. Toxoplasma gondii, Cryptosporidium parvum and Cyclospora caytenensis are among the coccidian parasites that can cause diarrhea in humans. There is no practical way of killing these parasites in food other than cooking. ARS scientists have found that low dose gamma irradiation (0.5 KGy cesium137) will kill these parasites in food. These results will be useful to the food industry, public health veterinarians and parasitologists.

Technical Abstract: The effect of 137Cs irradiation on unsporulated and sporulated Toxoplasma gondii oocysts was investigated. Unsporulated oocysts irradiated at ò0.4 to 0.8 kGy sporulated but were not infective to mice. Sporulated oocysts irradiated at ò0.4 kGy were able to excyst, and sporozoites were infective but not capable of inducing a viable infection in mice. Toxoplasma gondii was detected in histologic sections of mice up to 5 days but not at 7 days after feeding oocysts irradiated at 0.5 kGy. Raspberries contaminated with sporulated T. gondii oocysts were rendered innocuous after irradiation at 0.4 kGy. Results indicate that irradiation at 0.5 kGy is effective in "killing" coccidian oocysts on fruits and vegetables.

Last Modified: 10/22/2014