Transmission of Schistosoma mansoni from man to snail: laboratory studies on the influence of snail and miracidial densities on transmission success.

The relationship between infection success, the density of Schistosoma mansoni miracidia and the density of the snail host Biomphalaria glabrata was examined experimentally. Within laboratory infection arenas, the distribution of miracidial infections/snail was approximately uniform and the net rate of snail infection was directly positive binomial to miracidial density. In contrast, however, the rate of infection declined exponentially as snail density increased. Mathematical models are developed to aid in the estimation of infection rates and experimental results are discussed in the context of the transmission dynamics of schistosomiasis.