This study is part of a program to control and prevent dengue in a slum bordering on the grounds of the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil. The results obtained from a questionnaire and entomological survey called attention to problems pertaining to the information transmitted by public health campaigns and its interpretation, since many practices result from misunderstanding or forgetting preventive messages. Dengue-related data include most frequent vector breeding sites, people's knowledge, and dengue-related habits. The study's conclusions in terms of dengue prevention point to the need for drafting messages not only about ideal preventive practices but also teaching possible solutions: disseminating frequent messages throughout the year and not only seasonally and planning health education to join health professionals and the population in the search for sustainable dengue control alternatives.
The aim of this study was to compare the fecundity and fertility of B. glabrata and B. straminea by cross- and self-fertilization. To attain this objective, laboratory-raised strains of B. glabrata and B. straminea were used. The former originated from natural breeding grounds in the municipality Paulista, state of Pernambuco, Brazil. The latter originated from irrigation ditches in the municipality of Petrolândia, in the same state. Snail populations of B. glabrata and B. straminea were maintained for 240 days in laboratory. Their fecundity was evaluated by noting the number of egg-masses, eggs and eggs per mass. Their fertility was evaluated by the number of viable eggs and the hatching rate. B. straminea was markedly more fecund than B. glabrata through cross- and self-fertilization, namely: greater egg-mass; higher egg production and more eggs per mass. Regarding fertility, there seemed to be no preferential period for occlusion to occur or a trend in the rhythm of producing viable eggs.
This study focuses on the possibility of experimental hybridization among host snail species forIntraspecific and interspecific crossbreedings among host species have been described in the literature since the 1950s. Paraense (1955) and Paraense and Deslandes (1955) performed experiments based on intra-and interspecific crossbreeding. The former, intraspecific crossbreeding, aimed to establish these species' reproductive preferences, while the latter focused on the possibility of interspecific crossbreeding between B. glabrata and B. tenagophila, which were located 315 km from each other. The authors observed in these respective experiments that cross-fecundation is preferential and that the crossbreeding proposed was not viable, reporting reproductive isolation between the species of Biomphalaria studied. Interspecific crossbreedings between geographically isolated species were described by Barbosa: B. alexandrina (Cairo, Egypt) and B. glabrata (Recife, Pernambuco, Brazil) in 1956; B. straminea (Pernambuco, Brazil) and B. peregrina (Ecuador); B. tenagophila (São Paulo, Brazil) and B. peregrina (Ecuador) (Barbosa et al. 1958). Formation of fertile hybrid offspring was observed in these crossbreedings. The same author in 1964 commented on the natural hybridization of B. glabrata and B. tenagophila, reporting intermediate forms, explained by the proximity of the respective populations. Later on, Barbosa (1973) observed this process of natural hybridization in the Northeast of Brazil, between B. glabrata and B. straminea. Breeding sites previously colonized exclusively by B. glabrata were replaced by B. straminea over the course of three years. During the process of competitive exclusion, mixed forms were found, possibly resulting from interspecific crossbreeding. Such intermediate forms were no longer found during later field studies, showing their inability to persist in nature. This study's objectives were to observe the possibility of experimental hybridization between host species for Schistosoma mansoni in Brazil and to study the reproductive capacity and subsequent morphological characterization of the hybrid forms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.