N. Nihei et al., SOIL FACTORS INFLUENCING THE DISTRIBUTION OF ONCOMELANIA-QUADRASI, THE INTERMEDIATE HOST OF SCHISTOSOMA-JAPONICUM, ON BOHOL-ISLAND, PHILIPPINES, Annals of tropical medicine and parasitology, 92(6), 1998, pp. 699-710
Soil conditions essential to the survival of Oncomelania quadrasi on B
ohol Island in the Philippines were examined to clarify the factors li
miting distribution of the snail and to develop a method for breeding
large numbers of the snail in the laboratory. Soil samples in and arou
nd snail habitats were analysed and used for breeding experiments in t
he laboratory. Experiments using paddy soil derived from different par
ent materials revealed that the numbers of juvenile snails hatched var
ied widely between several soil samples. The best soils for reproducti
on generally had a pH of 5.6-7.9 and > 200 mg of available CaO/100 g.
These soil factors, in addition to shade and moisture, determine the o
ptimum conditions for the breeding of O. quadrasi in the field as well
as in the laboratory. The determination of the optimum conditions for
laboratory breeding of O. quadrasi and other intermediate snail hosts
should facilitate detailed study of the hosts and the development of
better methods to control or eradicate schistosomiasis and other snail
-transmitted diseases.