A total of 256 sites in 11 habitats were surveyed for
Biomphalaria
in Melquiades 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.
glabrata
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 sites and the presence of
Biomphalaria ova were strongly correlated with the occurrence of snails, and distance between houses and collection sites, as well as water velocity were inversely correlated with
Biomphalaria occurrence (p < 0.001). The strongest predictor o f Biomphalaria occurrence was the presence of tilapia fish in fishponds. Fourteen Biomphalaria (0.8% of all snails) found at 6 sites were infected with
Schistosoma mansoni
. Suggestions are made for the utilization of local people's knowledge in snail surveys and further studies are recommended on the possible use of tilapia for biological control of
Biomphalaria in fishponds, as well as modeling of S.
mansoni
transmission and reinfection.
