A potential vector of Schistosoma mansoni in Uruguay

Abstract

Susceptibility experiments were carried out with a Biomphalaria straminea-like planorbid snail (Biomphalaria aff. straminea, species inquirenda) from Espinillar, near Salto (Uruguay), in the area of the Salto Grande reservoir, exposed individually to 5 miracidia of Schistosoma mansoni (SJ2 and BH2 strains). Of 130 snails exposed to the SJ2 strain, originally infective to Biomphalaria tenagophila, 30 became infected (23%). The prepatent (precercarial) period ranged from 35 to 65 days. The cercarial output was irregular, following no definite pattern, varying from 138 to 76,075 per snail (daily average 4.3 to 447.5) and ending up with death. Three specimens that died, without having shed cercariae, on days 69 (2) and 80 after exposure to miracidia, had developing secondary sporocysts in their tissues, justifying the prospect of a longer precercarial period in these cases. In a control group of 120 B. tenagophila, exposed to the SJ2 strain, 40 became infected, showing an infection rate (33.3%) not significantly different from that of the Espinillar snail (chi 2 = 3.26). No cercariae were produced by any of the Espinillar snails exposed to miracidia of the BH2 strain, originally infective to Biomphalaria glabrata. Four specimens showed each a primary sporocyst in one tentacle, which disappeared between 15 and 25 days post-exposure, and two others died with immature, very slender sporocysts in their tissues on days 36 and 54. In a control group of 100 B. glabrata exposed to BH2 miracidia, 94 shed cercariae (94%) and 6 remained negative. Calculation of Frandsen's (1979a, b) TCP/100 index shows that "Espinillar Biomphalaria-SJ2 S. mansoni" is a vector-parasite "compatible" combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Susceptibility of Nectomys rattus (Pelzen, 1883) to experimental infection with Schistosoma mansoni (Sambon, 1907): a potential reservoir in Brazil

“…S. mansoni cercariae used in this study belonged to the Belo Horizonte (BH) strain maintained in B. glabrata snails and Swiss Webster mice (Paraense & Corrêa 1989).…”

Susceptibility of Biomphalaria amazonica and Biomphalaria occidentalis from Manso Dam, Mato Grosso, Brazil to infection with three strains of Schistosoma mansoni

“…The procedures for collecting feces of infected mice and for late exposure of snails to miracidia were those described by Paraense and Corrêa (1989), and the aquaria were kept at a room temperature of 24-26°C throughout the experiment. Snails were observed daily and, if any specimen happened to die, it was dissected and examined for development stages of the schistosome.…”

“…Snails were observed daily and, if any specimen happened to die, it was dissected and examined for development stages of the schistosome. To characterize the duration of precercarial period and the infection index, the screening techniques used to detect the positive snails were those described by Paraense and Corrêa (1989). The specimens that survived for 60 days after exposure without shedding cercariae were fixed in RaillietHenry's fluid, dissected and examined.…”

Susceptibility of Biomphalaria straminea (Dunker, 1848) from Serra da Mesa Dam, Goiás, Brazil to infection with three strains of Schistosoma mansoni Sambon, 1907

“…The strains have been kept in sympatric snails and female Swiss albino mice. The procedures for collecting feces of infected mice and for late exposure of snails to miracidia were those described by Paraense and Corrêa (1989), and the aquaria were kept at a room temperature of 24-26 o C throughout the experiment.…”

“…To characterize the duration of precercarial period and the infection index, the screening techniques used to detect the positive snails were those described by Paraense and Corrêa (1989). The specimens that survived for 60 days after exposure without shedding cercariae were fixed in Railliet-Henry's fluid, dissected and examined for developing stages of the schistosome.…”