Schistosoma mansoni cercarial host location and infection under simulated natural conditions in Egypt

This study was performed in water ditches under simulated natural conditions in Egypt to elucidate the effect of various environmental factors on Schistosoma mansoni cercarial host location and infection of the definitive host [using albino mice]. Evaluation of these factors was dependent on both infection rate of exposed mice as well as the schistosome worm load under the same experimental conditions. The seasonal water temperature proved to be a very important factor and this was proven by the infection rate of mice and the worm load recovered were lower in January and April [16°C and 22°C midday water temperature] and much higher in July and October [29°C and 25°C]. The daytime factor is similarly important as temperature illustrated by the schistosome infection of mice groups exposed at 8-10 am was much higher than in groups exposed between 1pm and 3pm [p<0.001]. The greatest infection rate of mice and worm load were obtained when the shedding snails were close to the exposed group of mice. Both criteria increased with the increase of cercarial density in the water. The length of exposure period is also an extremely important factor for schistosome infection, being highest 87.5% [p<0.001] in3 hours exposure period. Infection rate was found to be 88.2% and 55.6% of shedding snails were located at water surface and midway to the bottom, respectively, and no infection occurred when located at the bottom. The schistosome infection of mice decreased in presence of increasing density of the floating plant Eichhornia crassipes in the ditch water, but low condensation of the submersed plant Ceratophyllum demersum appeared to have stimulating effect

Identification and immunological characterization of Echinostoma liei antigens: preliminary study for validation of its use in schistosomiasis control program

Several studies have proposed the use of larvae of Echinostoma in schistosomiasis biological control program, since Echinostoma rediae attack and even destroy S. mansoni sporocysts probably by induction of host's inflammatory response when they are in the same molluscan. The objective of the present work was to identify and immunologically characterize E. liei antigens to be presented as a promising tool in schistosomiasis control program. Two E. liei antigens were prepared namely metacercarial and adult worm antigens in addition to Schistosoma soluble egg antigen [SEA] and Schistosoma worm antigen [SWAP]. Analysis of the four antigens by sodium dodecyl sulphate polyacrylamide gel electrophoresis [SDS-PAGE] revealed a number of bands except for the metacercarial antigen of E. liei which appeared as a single band. Immunoblotting revealed three common bands between SEA, SWAP and E. liei worm antigen corresponding to 17, 29 and 97 kDa. Detection of specific total IgG and IgG4 isotype in sera of S. mansoni infected patients were measured by ELISA using all four studied antigens. The levels of both IgG and IG4 isotype showed no statistical significant difference between schistosomal SEA, SWAP and worm E. liei antigens. On the other hand, metacercarial antigen revealed statistically significant lower levels of both IgG and IgG4 when compared with schistosomal SEA [p< 0.05]. The highest sensitivity and specificity rates for detection of specific total IgG and IgG4 isotype were recorded when using schistosomal SEA. Owing to its rather promising results, further studies are needed to investigate the possible validity of using E. liei adult worm antigen in snail immunization against schistosomiasis especially in endemic areas where re-infection is commonly encountered

Intraperitoneal injection of echinostome antigens confers resistance to schistosomal infection in murine model

The effect of immunization protocol against S. mansoni infection with purified metacercarial antigen from E. liel alone or combined with BCG on resistance to S. mansoni infection and associated immunoparasitological changes in murine experimental model was studied. The results revealed highly significant reduction in worm burden and hepatic and intestinal tissue egg loads were observed on comparing the two immunized groups [purified metacercarial antigen alone or purified metacercarial antigen plus BCG] with the infected control group [p> 0.001]. Moreover the greatest reduction in the worm burden was observed in group injected with purified metacercarial antigen pluse BCG. A significant reduction [p> 0.001] was observed in granuloma diameter in the two immunized groups relative to infected control. However, the greatest reduction in granuloma diameter was noticed in group II [purified metacercarial antigen pluse BCG]. No significant difference was observed in granuloma diameter berween the two immunized groups. Anti-SEA serum specific immunoglobulins in group I and group II showed a significant increase in both IgG and IgM [p> 0.05] compared to the infected control group. A higher significant increase was found in the specific immunoglobulin isotype IgGI [p> 0.001] in both group I and II compared to infected control group. In conclusion, our findings showed that multiple intraperitoneal adminestration of purified metacercarial antigen induce highly significant reduction in worm burden, hepatic and intestinal tissue egg loads and granuloma size 8 weeks post infection