Competitive displacement of Biomphalaria glabrata by B. straminea

Barbosa, Frederico Simões

doi:10.1590/s0074-02761987000800024

Cited by 10 publications

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“…The introduction of B. straminea strains which are resistant to S. mansoni infection into habitats of B. glabrata has been sought as a promising biological control measure due to the greater fecundity of the former snail species (Michelson & Dubois 1979). Field data from the endemic area of schistosomiasis in Northeastern Brazil has indicated that B. straminea can competitively displace B. glabrata (Barbosa 1987). However, the relatively high rates of natural infection obtained for B. straminea in the present study should discourage the introduction of a resistant strain of this species in this area.…”

Section: Discussioncontrasting

confidence: 59%

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco, Brazil

Favre

Pieri

Zani

et al. 2002

Mem. Inst. Oswaldo Cruz

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In the Brazilian state of Pernambuco, schistosomiasis exhibits an epidemiological profile of chronic infection and persistent reinfection in the rainforest area (Zona da Mata). Heavy infections are also frequent in the coastal area (Barbosa et al. , 2001. Despite the amount of data amassed over the years and the advances in immunological and therapeutic clinical research, control of schistosomiasis transmission still represents a challenge for government institutions (Barbosa & Coimbra 2000). Although morbidity indices remain low, the prevalence of infection and the rate of reinfection have remained high in rural areas despite repeated treatment with oxamniquine , Favre 1999.Longitudinal studies of infected snails in critical areas, in parallel with application of control measures may shed light on why control measures fail. Nevertheless, few have been carried out (Dazo et al. 1976, Gundersen et al. 1990).In Pernambuco, there are two intermediate host species of Schistosoma mansoni: Biomphalaria straminea and B. glabrata. The first species is widespread over the Agreste, a zone of transitional vegetation, and the Zona da Mata, where it maintains high endemicity levels despite the low rates of natural and experimental infection (Paraense & Corrêa 1989). The second species, with infection rates reaching up to 20%, is mainly found in coastal areas, and remains responsible for several active foci of transmission .The present study aims to assess, on a monthly basis over a period of four years, the relative abundance and the natural infection of B. straminea and B. glabrata by S. mansoni in two representative localities in an endemic area in the state of Pernambuco, where infected persons were treated periodically with oxamniquine. In addition, tests were carried out to ascertain the susceptibility of snail species found in these localities to local parasite strains. MATERIALS AND METHODSTwo rural localities sharing similar sociodemographic characteristics and displaying medium levels of endemicity in relation to schistosomiasis (prevalence ranging from 30% to 40%), populated by distinct intermediate host species, were chosen after a preliminary stool survey and the application of a home questionnaire as described by Moza et al. (1998). Nine stool surveys by the Kato-Katz method (Katz et al. 1972) were undertaken every three months in both localities and individuals who tested positive for S. mansoni were treated with oxamniquine ), in March 1995, June 1995, March 1997 and March 1998 Characterization of the study area -Ecological features relevant to schistosomiasis transmission were recorded, including water-contact habits and rainfall. As recommended by Olivier (1973), sketch maps were used to display the location of houses, land use and water resources of each locality.Malacological survey -Snail breeding sites regarded as potential of transmission foci were identified in both localities. Snails were collected monthly from predetermined stations over the four years of the follow-up sur-+ Corresponding

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Section: Discussioncontrasting

confidence: 59%

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco, Brazil

Favre

Pieri

Zani

et al. 2002

Mem. Inst. Oswaldo Cruz

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“…Studies under semi-natural and field conditions have revealed the competitive superiority of B. straminea over B. glabrata 3,4,5,6,8,9 . Among the factors involved, in addition to low susceptibility to infection by S. mansoni and greater resistance to desiccation, better dispersal capacity and higher vagility were noted for the former species 6,7,14,27 .…”

Section: Introductionmentioning

confidence: 99%

Comparative study of the fecundity and fertility of Biomphalaria glabrata (Say, 1818) and Biomphalaria straminea (Dunker, 1848) in a laboratory through self-fertilization and cross-fertilization

Costa

Grault

Confalonieri

2004

Rev. Inst. Med. trop. S. Paulo

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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.

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“…These observations refl ect the possible occurrence of interspecifi c competition between these species. In fact, the competition and elimination of B. glabrata by B. straminea has been reported in experimental and natural conditions 38,[40][41][42] , and we cannot rule out the possibility that the competitive advantages of B. straminea also exist with respect to B. tenagophila. However, the factors related to the overlap of one species of snail over another are complex, and changes in the environment appear to have great importance 17 .…”

Section: A B C D E Fmentioning

confidence: 86%

The Pampulha reservoir remains a potential urban focus of schistosomiasis mansoni in Brazil: changes in the occurrence patterns of Biomphalaria species and a new record of the parasite

Pinto

Mati

Melo

2013

Rev. Soc. Bras. Med. Trop.

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Introduction:The Pampulha reservoir has long been a focus of schistosomiasis transmission in Belo Horizonte, State of Minas Gerais, Brazil. The last malacological study conducted in this urban reservoir was more than two decades ago, and thus, an update on the distribution of the species of Biomphalaria as well as new data on the presence of Schistosoma mansoni in this water body are required. Methods: The current distribution of Biomphalaria spp. in the Pampulha reservoir and their infection with S. mansoni was evaluated during 55 malacological surveys conducted between 2009 and 2012. Results: Biomphalaria straminea displayed a high population density and distribution, and 13.7% (2,233/16,235) of the specimens collected were infected with larval trematodes other than Schistosoma mansoni. Biomphalaria tenagophila and Biomphalaria glabrata, species currently presenting a restricted distribution and small populations, displayed trematode infection rates of 15.2% (98/644) and 13% (83/640), respectively. Thirteen (2%) specimens of B. glabrata were found to be infected with S. mansoni. In addition, a historical review based on previous and new data on the occurrence patterns of Biomphalaria species in this reservoir is presented. Conclusions: The results indicate that the Pampulha reservoir remains a potential focus of urban schistosomiasis in Brazil, and signifi cant changes in the occurrence patterns of Biomphalaria species were verifi ed.

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Competitive displacement of Biomphalaria glabrata by B. straminea

Abstract: Data on the interaction between populations of closely related species of Biomphalaria, B. glabrata and B. straminea, are presented in the current paper. Laboratory and field observations and experiments have shown that B. straminea has competitive advantages over B. glabrata.

Cited by 10 publications

References 0 publications

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco, Brazil

Longitudinal Study on the Natural Infection of Biomphalaria straminea and B. glabrata by Schistosoma mansoni in an Endemic Area of Schistosomiasis in Pernambuco, Brazil

Comparative study of the fecundity and fertility of Biomphalaria glabrata (Say, 1818) and Biomphalaria straminea (Dunker, 1848) in a laboratory through self-fertilization and cross-fertilization

The Pampulha reservoir remains a potential urban focus of schistosomiasis mansoni in Brazil: changes in the occurrence patterns of Biomphalaria species and a new record of the parasite

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