Experimental infection with Schistosoma mansoni of Biomphalaria straminea from different parts of the Northeast of Brazil

Abstract

In the western part of the State of Bahia Biomphalaria straminea and B. glabrata both occur, but in the majority of cases they do not share the same habitat. In the State of Ceará, however, B. straminea is the sole snail host of Schistosoma mansoni. In this survey, no naturally infected B. straminea was found among snails collected from Bahia and Ceará, evidently because of the very low infection rates. The susceptibility of laboratory-reared specimens to infection with a Puerto Rican strain of S. mansoni was then tested experimentally. In general, the snails showed very low susceptibility. The infection rates were 1.1% among snails from Redenção (Ceará); 2.3% in those from Pentecoste (Ceará); 2.9% in snails from São Desidério (Bahia), while they were very high among an albino strain (NIH) of B. glabrata used as control. Another group of B. straminea from São Desidério was exposed to a Bahian strain of S. mansoni and the infection rate was still very low (3.6%) Apparently, the very low susceptibility of B. straminea, despite high snail density, is correlated with moderate infection rates with S. mansoni among humans, as shown by the results of stool examinations conducted by SUCAM in the municipalities of Redenção and Pentecoste, in Ceará.

Parasite―host coevolution and geographic patterns of parasite infectivity and host susceptibility

“…The data include results from one study of pfeifferi in Zimbabwe (Manning 1994), one study of glabrata in South America (Paraense & Correa 1963 a), one study of Bi. straminea in Brazil (Malek & Rouquayrol 1986) and four studies of Bi. tenagophila in Brazil and elsewhere in South America (Paraense & Correa 19636, 1978;Chieffi 1975a;Borda & Pellegrino 1976).…”