Evaluation of The Effect of Radioactive Cobalt-60 and Ultra-Violet Rays onGiardia lambliaCysts and Their Infectivity to Rodents

Abstract

Giardia lamblia (Giardia intestinalis or Giardia duodenalis) is a flagellated enteric protozoan parasite, unicellular eukaryotic microorganism that commonly causes diarrheal disease worldwide. It is the most common intestinal protozoan parasite, causing diarrhea in children, especially those with malnutrition or with immunodeficiency (Campbell, 1992 and Hakim et al., 2011). It alternates between two morphological forms cyst and trophozoite, where trophozoite colonizes the proximal small intestine and is responsible for the production of diarrhoea and malabsorption and cyst is the stage which is able to exist outside the host in a suitable environment and is the form of the parasite by which giardiasis is usually transmitted (Farthing et al., 2008). The prevalence of Giardia is 2-7% in industrialized countries and 40% in developing countries while in Egypt prevalence varies from 10% in some areas to reach 44% in other areas (Hakim et al., 2011). The cause of diarrhea and malabsorption in Giardia infection is likely to be multifactorial, including the host immune response to the pathogen as well as, cytopathic substances secreted by the parasite. Besides that, it has been suggested that Giardia may cause pathology by alteration of the bile content or endogenous flora of the small intestine which in turn could affect the absorption of the gut (Sinnis, 2009). This study was conducted to evaluate the effect of radioactive Cobalt-60 and 254 nm-UV irradiation on infectivity of Giardia lamblia cysts to mice, and examining their ability to reduce the Giardia lamblia infectivity. The effect of radiation was tested by oral inoculation of BALB/c mice with the irradiated human-derived cysts. The study was conducted on 60 BALB/c mice, aged four to eight weeks old and. They were divided into six groups, 10 mice in each group. Group (1) includes 10 mice infected with a suspension of human derived Giardia lamblia cysts irradiated with Cobalt-60 in a dose of 0.25 KGy which gave an intensity of 1.25 MeV at a distance of 60 cm on an area of 20x20 cm with 0.5 bolus for 25 min, group (2) includes 10 mice infected with a suspension of human-derived Giardia lamblia cysts irradiated with 254-nm UV rays, with temperature 4.2 ◦C, exposure time 120 seconds and 20 mJ cm-², group (3) includes10 mice infected with human-derived, non-irradiated Giardia lamblia cysts, group (4) includes 10 non-infected mice that received water irradiated with 0.25 KGy of Cobalt-60, group (5) includes 10 non-infected mice that received water irradiated with 254 nm UV rays and group (6) includes 10 non-infected mice received non-treated water. Groups 3, 4, 5 and 6 were considered as control groups. The infectivity was assessed based on stool analysis for the mice on day 0 to exclude their previous infection then on day 9, 10, 11, 12 and 21, the presence of trophozoites in mice duodenal aspiration and the presence of histopathological changes in the small intestine of mice. Stool samples were collected from mice of the six groups and examined using direct stool examination and formol ether concentration technique. After several trials using different doses of Giardia cyst we chose cyst dose 106 to use. By using direct stool examination, in group (1), infectivity maximum intensity was in day 11 with infectivity percentage 10% while in group (2), no mice appear to be infected all through the 21 days with infectivity percentage 0%. In Group (3), mice showed infectivity percentage 100% and maximum intensity was on day 12. On the other hand, groups 4, 5 and 6 which are control groups showed 0% infectivity. By using formol ether concentration technique, in group (1), infectivity maximum intensity was in day 11 with infectivity percentage 20% while in group (2), no mice appear to be infected all through the 21 days with infectivity percentage 0%. In group (3), infection started to appear on day 9 with infectivity percentage 20% on the 10th day then infection percentage increased to 80% on day 11 then increased to 100%. Groups 4, 5 and 6 showed 0% infectivity. Duodenal aspiration from mice small intestine and examination of the aspirate for the presence of Giardia lamblia cysts or trophozoites: If no cysts were observed in the feces but inactive trophozoites were observed in the small intestine this was considered as weak infection, while if no cysts were observed in the feces but active trophozoites were observed in the small intestine this was considered as moderate infection, while if cysts were observed in the feces and many active trophozoites were observed in the small intestine this was considered as strong infection. We found that group (1) showed 40% infectivity (20% were weak infection and 20% ranged from moderate to strong infection), group (2) showed no infectivity, group (3) shows 100% strong infectivity, while Group 4, 5 and 6 showed neither trophozoites nor cysts on examination.