Effect of Schistosoma mansoni infection on physiological gastrointestinal transit and contractility

The work aimed to study the effect of Schistosoma mansoni (S. mansoni) on gastrointestinal transit and contractility of the colonic muscles of two subgroups of experimental mice, infected by 50 & 200 cercaria/mouse respevtively, at 8th & 12th week postinfection (PI). In addition, the histopathologic changes in the colon, and the immunological changes of the host were studied at different durations. At 8th weeks PI, in both subgroups, gastrointestinal transit was statistically significant decreased, in concurrent with statistically significant increase in the colonic muscle contractility compared to the controls. The colon was inflamed as shown by mucosal inflammatory infiltrates, with large size and number of schistosomal granulomas. The serum antigen was absent, while the serum antibody was detectable at low titre. At 12th weeks PI, there was a more statistically significant decrease in gastro-intestinal transit, and increase in the colonic muscle contractility. The colon was still inflamed, but the granulomas were reduced in size and in number, with increase in the fibrocytes density. These alterations coincided with absence of serum antigen and increase in the antibody titre. All changes were more pronounced in the 2nd group of mice (200 ceraria/mouse) than the 1st one (50 cercaria/mouse). So, intestinal schistosomiasis is associated with great structural, functional and immunological changes, related to the time course and the infection intensity which may be involved in the pathogenesis and clinical manifestations of the disease.