The distribution of Biomphalaria spp. in different habitats in relation tophysical, biological, water contact and cognitive factors in a rural area in Minas Gerais, Brazil

A total of 256 sites in 11 habitats were surveyed for Biomphalaria in Melqu iades rural area (State of Minas Gerais) in August and November 1999 and in March 2000. Of the 1,780 Biomphalaria collected, 1,721 (96.7%) were B. gla brata and 59 (3.3%) B. straminea. Snails were found in all habitats except in wells, with the largest mean numbers in tanks, seepage ponds and canals, and the smallest numbers in springs, rice fields and fishponds. People's knowledge of the occurrence of Biomphalaria at the collection site s and the presence of Biomphalaria. ova were strongly correlated with the o ccurrence of snails, and distance between houses and collection sites, as w ell as water velocity were inversely correlated with Biomphalaria occurrenc e (p < 0.001). The strongest predictor of Biomphalaria occurrence was the p resence of tilapia fish in fishponds. Fourteen Biomphalaria (0.8% of all sn ails) found at 6 sites were infected with Schistosoma mansoni. Suggestions are made for the utilization of local people knowledge in snail surveys and further studies are recommended on the possible use of tilapia for biologi cal control of Biomphalaria in fishponds, as well as modeling of S. mansoni transmission and reinfection.