Susceptibility of Schistosoma japonicum miracidium to Oncomelania hupensis snails at different densities and distances:a primilinary experimental observation

To investigate the susceptibility of Oncomelania snails at different densities and to miracidium of Schistosoma japonicum,snails at 1,2,3 and 5 m,each with densities of 5,10,50 and 100 per package were infected with 20 000 freshly hatched miracidia in the field,and transferred to laboratory 4 h post-infection.All snails were dissected for infection eight weeks later.At sites of 1,2,3 and 5 m,the infection rates of snails were 7.06%,4.35%,2.47% and 1.23%,4.55%,4.44%,4.11% and 2.27%,2.62%,1.58%,1.29% and 1.1%,2.36%,4.04%,2.73% and 1.5%,respectively for snail densities of 5,10,50 and 100 per package.It is indicated that the infection rates of snails are inversely proportional to the distances from the miracidium-disposal sites,but no linear relation between snail infection rate and snail density.