Differential susceptibility of Biomphalaria tenagophila populations to infection with a strain of Schistosoma mansoni.

Experiments to determine the susceptibility of Biomphalaria tenagophila from 20 localities over the species range exposed to a strain of Schistosoma mansoni showed widely varying infection rates, from 0% to 91.5%, this latter having been observed in a sample from an area where the natural infection rate of B. tenagophila has been the highest in the country. Comparison with similar studies involving B. glabrata seems to indicate that a process of adaptation between S. mansoni and B. tenagophila is evolving, the 2 organisms having reached a high degree of compatibility in a few areas. The present results point to the possibility of expansion of schistosomiasis to a wide South American area where B. tenagophila occurs.