Biological and morphological characteristics of Schistosoma mansoni from Ribeira Valley, State of São Paulo, Brazil: I - susceptibility of Biomphalaria tenagophila snail to sympatric S. mansoni strain

Abstract

In the São Paulo State, Brazil, where the Biomphalaria tenagophila is the intermediate host, the Ribeira Valley is an important endemic schistosomiasis mansoni area. During last eleven years there has been intense control measures focusing on schistosomiasis. The efforts have been concentrated in the municipalities of Pedro de Toledo and Itariri. We determined the susceptibility of B. tenagophila to sympatric strain of S. mansoni, both recently isolated from Itariri field. In 1988, this strain was isolated and maintained in the experimental model: Swiss mice - sympatric B. tenagophila. The second generation of the worm was evaluated. The snail were divided in the three groups of 60 snails each. One group was exposed to 1 miracidium and other to 10. The third group was the control. The mortality and the shedding of cercariae were checked during 78 days. After that, the positive snails were observed until they ceased to shed cercariae. The exposed molluscs showed mortality rates of 23% and 31% and infection indexes were of 8% and 60% to 1 and 10 miracidia respectively. The mortality was of 22% in the control group. The periods of shedding cercariae in the two groups were 82 and 104 days. We can conclude that B. tenagophila is an effective intermediate host to the sympatric strain of S. mansoni sympatric strain

The effects of the experimental infection from a focus of transmission of Schistosoma mansoni in a population of Biomphalaria tenagophila (D'Orbigny, 1835) in the region of "Vale do Ribeira de Iguape", Brazil

“…The laboratory population had a long patent phase -as long as 119 days (17 weeks) for the few individuals that survived infection. This finding is similar to the results reported by FIGUEIREDO et al 6 , who observed a patent phase for B. tenagophila (also from Ana Dias) that lasted 104 days (14.8 weeks). The main implication of a long patent period is the maintenance of an active schistosomiasis focus.…”

“…The infection rate recorded for the experimental population was 58.8%, very close to the result reported by FIGUEIREDO et al 6 , who found an infection rate of 60.0% for B. tenagophila from Itariri. PARAENSE & CORRÊA 15 also experimentally infected various B. tenagophila populations from 18 different locations in Brazil and found infection rates varying between 0.0% and 91.5%, the latter figure being for a B. tenagophila population that was also from Itariri.…”

Polimorfismo dos genes mitocondrial 16S rRNA e nuclear ITS-2 em populações de Biomphalaria tenagophilada bacia litorânea do estado de São Paulo e estudo da suscetibilidade dos caramujos ao Schistosoma mansoni

“…Tabela 1 -Número de casos autóctones de esquistossomose no estado de São Paulo, distribuído por bacia hidrográfica nos períodos de 1981 a 2008 (Zanna, 2010;CVE, 2008. (Figueiredo et al, 1992;Guimarães et al, 2010).…”

“…5%, para B. tenagophila de Itariri, distrito de Ana Dias, exposta a 10 miracídios da linhagem SJ Figueiredo et al (1992). obtiveram taxa de infecção de 60%, quando a exposição A infecção experimental de B. tenagophila de Caraguatatuba do bairro de Indaiá mostrou taxa de infecção de 50% a 73,3% após a exposição à linhagem SJ e 60 a 76,7%, quando a exposição foi pela linhagem SJS.…”