title: Studies on the use of cobalt-60 irradiation to control infectivity of Toxoplasma gondii cysts.
abstract: Mouse brains harboring the Chinese NT strain of Toxoplasma gondii cysts were homogenized with normal saline and irradiated with cobalt-60 gamma rays at various doses. The homogenate was introduced intraperitoneally into NIH mice or per os into kittens. Loss of infectivity was confirmed according to the following criteria: no cyst found in mouse brain impression smears on the 50th day after inoculation; no oocyst found in feces of kittens 3-15 days after inoculation; subinoculation in mice and a negative IHA test. All bioassays, parasitological examinations and serological tests in the control group gave positive results. Activity of radioactive source: 10 KCi; uniform dosage: 1238 rad/min; dose range of irradiation: 0.1-1.0 KGy. Minimal effective dose of gamma rays to control infectivity of T. gondii cysts was 0.55 KGy. Infectivity of bradyzoites irradiated with gamma rays at a dose of 0.45 KGy decreased by 10,000 times. Minimal effective dose of gamma rays to control infectivity of American ME-49 and Ts-2 strain, is slightly higher (0.6KGy) than that of NT strain. These studies present useful data for practical use of cobalt-60 to control infectivity of T. gondii in meat products.
authors.affiliation: Institute of Parasitic Diseases, Zhejiang Academy of Medical Sciences, Hangzhou, People's Republic of China.
authors.forename: C C
authors.initials: CC
authors.lastname: Song
authors.forename: X Z
authors.initials: XZ
authors.lastname: Yuan
authors.forename: L Y
authors.initials: LY
authors.lastname: Shen
authors.forename: X X
authors.initials: XX
authors.lastname: Gan
authors.forename: J Z
authors.initials: JZ
authors.lastname: Ding
authors.forename: Y F
authors.initials: YF
authors.lastname: Duan
mesh_terms: D000818:Animals; D001681:Biological Assay; D002415:Cats; D003037:Cobalt Radioisotopes / Q000627:therapeutic use*; D005260:Female; D005720:Gamma Rays; D051379:Mice; D014122:Toxoplasma / Q000472:pathogenicity / Q000528:radiation effects*; D014124:Toxoplasmosis, Animal / Q000517:prevention & control*
chemical_list: D003037:Cobalt Radioisotopes