ABSTRACT
Mercury is one of the most widely distributed heavy metal which incriminated in the environmental pollution. Evidence is emerging that chronic exposure to mercury may elicit immunomodulation with enhanced host susceptibility to bacterial, viral and parasitic infection. Therefore a special attention is payed in this study to test the impact of subchronic mercury exposure on the immune response and the pathogenesis of experimental cryptosporidiosis. One hundred and sixty, parasite free, albino mice were used in this study and were divided Into four groups:-Group [1]: consisted of 50 mice which received an oral daily dose of mercury for 28 days before infection with Cryptosporidium oocysts. Group [2]: consisted of 50 mice which infected with Cryptosporidium oocysts without mercury treatment, Group, [3]: consisted of 50 mice, which received mercury treatment only and Group [4]: consisted of 1.0 mice with no infection and no mercury treatment [control group]. The influence of the subchronic mercury exposure on the pathogenesis of cryptosporidiosis will be assessed by counting the fecal oocysts, histopathological examination of different organs of infected mice and biochemical estimation of the glycogen and protein contents in both liver and heart tissues at early stage of infection, Lastly, the levels of IFN-gamma and IL10 in the sera will be measured during the course of experiment. The results of the present work showed that group [1] had shorter prepatent period as fecal oocysts could be detected from first day post infection, remained infected longer and shed more oocysts with higher mortality rate as compared to group [2]. In addition, a significantly higher number of endogenous stages were detected in group [1] with severe villous atrophy and heavy infestation with the endogenous stages than in group [2]. Regarding the levels of glycogen and protein, groups [1and 2] showed statistically significant decrease in the level of glycogen in liver and heart tissues whereas, the level of protein increased in the liver unlike the cardiomyocyte that showed marked protein decrease as compared to other groups. Moreover, there was a statistical significant increase in the levels IFN-gamma and IL10 in group [2] as compared the lower levels detected in group [1], Therefore, the result of the present work strongly support the immunosuppressive effect of mercury on experimental cryptosporidiosis as evident.by flaring up of the intestinal infection with the extraintestinal spread of the parasite as well as the induction of functional impairment in liver and heart tissues. Therefore, these results would spotlight on the wide spread environmental pollution with mercury which may be incriminated in the flaring up of the opportunistic parasites specially among children and its possible hazardous effect on their health