Rodents as reservoir hosts in the transmission of Schistosoma mansoni in Richard-Toll, Senegal, West Africa

More than 2000 animals belonging to six different rodent species and one in sectivore species were examined for infection with schistosomes in the regi on of Richard-Toll, Senegal. Two murid rodents, Arvicanthis niloticus and M astomys huberti, were found infected with Schistosoma mansoni. Prevalences were about 5% for both rodent species with a mean worm burden of about 20 w orms per host. The sex-ratios of S. mansoni worms were always biased toward s males. Prevalences and worm burdens, although similar in both male and fe male rodents, increased significantly with age. The highest prevalences and worm burdens were found near habitations and decreased significantly with the distance from the town of Richard-Toll. Eggs were also observed in the liver and faeces of the two naturally infected rodent species. The results suggest that rodents participate in the transmission of intestinal schistos omiasis in Richard-Toll but the human population is the main source of infe ction. The genetic resemblance between human and murine isolates of S. mans oni suggests that further epidemiological studies are needed in this region of Senegal.