Oral immunization of mice against Schistosoma mansoni using drinking water from trays containing Biomphalaria alexandrina infected with Schistosoma mansoni.

Water collected from trays containing Biomphalaria alexandrina infected with Schistosoma mansoni at the time of cercariae shedding (SmISW) and trays containing clean, non-infected, B. alexandrina (NISW) and underground water (UW), were filtered used as a drinking water for 3 groups of albino mice males. After two months, blood samples were collected from the 3 groups and serum was tested for anti-cercarial IgG, then mice were infected with 150 S. mansoni cercariae. Eight weeks after infection, mice were perfused and adult S. mansoni worms were counted. Anti-cercarial IgG was positive in 23 (82.1%) out of the 28 samples collected from mice drinking SmISW and only in 2 (9.5%) out of the 21 samples collected from mice drinking NISW, while all samples collected from mice drinking UW were negative for anti-cercarial IgG (X2=45.897; P<0.001). Worm load was significantly lower in the group of mice drinking SmISW than mice drinking NISW (P=0.032) and mice drinking UW (P=0.02). In mice drinking SmISW, adult worm count showed significant negative correlation with anti-cercarial IgG concentration (Kendall's taub =-0.325 and P=0.018). The results indicate that antigens present in drinking water stimulate a level of immunity against schistosomiasis, (inhabitants of endemic areas) resulting in a lower intensity and severity of infection. Also, it may reduce the specificity of serological tests used for diagnosis of Schistosoma infection, based on antibody determination.