Experimental Study on the Use of Cobalt-60 Irradiation in the Inactivation of Giardia lamblia Cyst

Background: Giardia lamblia is distributed worldwide and especially in areas with poor sanitary conditions. Waterborne outbreaks of giardiasis have been reported all over the world; their studies have usually shown defective water treatment plans. Objective: The present work aimed to evaluate the effect of radioactive Cobalt-60 on the viability and infectivity of Giardia lamblia cysts for possible future use in disinfection purposes. Subjects and Methods: The study was conducted on a total of 120 mice which were divided into four groups: A, 50 mice infected with a stool suspension containing human derived nonirradiated Giardia lamblia cysts and served as control; B,50 mice infected with a suspension containing human derived irradiated Giardia lamblia cysts which was subjected to direct field beam of Radioactive Cobalt 60 , a type of Gamma irradiation, in a dose of 0.25 Kilogray (KGY); C,10 mice inoculated with irradiated distilled water which was subjected also to Radioactive Cobalt 60 in a dose of 0.25 Kilogray (KGY); and finally D,10 mice as normal control. The degree of infectivity was assessed based on stool examination and the presence of histopathological changes in the small intestine of mice. In the present study, the detection of Giardia lamblia in stool from different mice groups was performed using three different methods: the simple sedimentation method, the Parasep faecal parasite concentrator and the immune-chromatographic fast assay. Results: The results showed that the cysts that received the radioactive cobalt were unable to induce infection in mice; while the infectivity of the non-irradiated cysts was found to be 95.5% by immunological method (the rapid copro- antigen) and by histological examination Giardia lamblia trophozoites were detected in 66.6% of the mice of this group. The most sensitive method for the detection of G. lamblia in stool of different mice groups was the immunechromatographic fast assay followed by the Parasep and the least sensitive method was the simple sedimentation method. Conclusion: The present study highlighted the effectiveness of low dose radioactive cobalt -60 in prevention of G. lamblia infection and indicated that it can be used to prevent infectivity and as a mean of water treatment