Study of the snail intermediate hosts for Schistosoma mansoni on Itamaracá Island in northeast Brazil: spatial displacement of Biomphalaria glabrata by Biomphalaria straminea

Abstract

Abstract. In 2012 a malacological survey of the breeding sites of Biomphalaria glabrata and B. straminea, the two intermediate host snails of Schistosoma mansoni, was carried out on Itamaraca Island in Pernambuco, Brazil. This study has now been extended by studying the competition between the two species. Snails were collected and dissected to identify the species and tests were performed to verify S. mansoni infection. Student's t test was used to compare the proportion between the two species and their breeding sites and a parasitological survey was conducted among local residents, using the Kato-Katz method. The spatial distribution of the two snail species was determined using TerraView, while a snail density map was constructed by Kernel estimate. The survey identified two breeding sites for B. glabrata with 17 specimens and 19 breeding sites for B. straminea with 459 snails, all of them negative for S. mansoni infection. The statistical analysis revealed that the proportion of the numbers of specimens and breeding sites of B. straminea (37.84 ± 9.01) were significantly greater than those of B. glabrata (8.50 ± 6.50). Parasitological examinations from 41 residents diagnosed two cases of schistosomiasis with parasite loads of 60 and 84 eggs per 1 g of stool, respectively. This indiction of a competitive process between the two snail species requires monitoring of schistosomiasis in the resident and travelling human populations occupying this environment, which could potentially result in social and economic changes on the island risking its attraction as a centre for eco-tourism.

Modelling of the distribution of Biomphalaria glabrata and Biomphalaria straminea in the metropolitan region of Recife, Pernambuco, Brazil

“…in the forest zone of Pernambuco where this species is now common . The replacement process of B. glabrata by B. straminea in the MRR was reported by Barbosa et al in 2014. The uncertainty found in this study was very similar to that seen by Guimarães et al in 2012.…”

“…It has been pointed out that competitive exclusion influences the distribution of the species since the 1970s, i.e. B. straminea showing dominance due to the biological characteristics of this species, such as high reproductive rate, invasiveness and relatively ease in adaptation to new environments (Barbosa et al, 2014). This has allowed its establishment in new locations, bringing with it the possible endemicity of schistosomiasis, e.g.…”

“…Presence of schistosomiasis has been described in 18 of the states of Brazil, including the Federal District, and its occurrence is directly linked to the presence of Biomphalaria (Brazilian Ministry of Health, 2009). In the state of Pernambuco, B. straminea is endemic in the Zona da Mata region, with some records also on the coast of this state, while B. glabrata occurs in the coastal region (Barbosa et al, 2010(Barbosa et al, , 2014. Knowledge of these snails' habitats, behaviour in relation to climate change and geographical distribution is essential for guiding measures for prevention and control of schistosomiasis.…”

Predicting frequency distribution and influence of sociodemographic and behavioral risk factors of Schistosoma mansoni infection and analysis of co-infection with intestinal parasites

“…Most specialized studies map snail infections or relate snail distributions to schistosomiasis prevalence with the objective of identifying high-risk areas, by studying human water contact sites (Barbosa et al, 2004(Barbosa et al, , 2014Kloos et al, 2004;Araujo et al, 2007). It is clear that the ability to predict the spatial distribution of infections improves our understanding of co-endemicity and its distribution, which can be used as evidence base for the spatial orientation of large integrated control programs (Brooker and Clements, 2009).…”

Spatial analysis for the identification of risk areas for schistosomiasis mansoni in the State of Sergipe, Brazil, 2005-2014

“…In Brazil, the disease occurs in all regions, with areas of concentration in the Northeast and in the State of Minas Gerais (4) . According to the Schistosomiasis Control Program [Programa de Controle da Esquistossomose (PCE)] data, there were 7.1 million exams of feces in 1,060 endemic municipalities -with a positivity for Schistosoma mansoni of 5.4% -performed in the period from 2008 to 2012 (8) . In Northeastern Brazil, the planorbidae Biomphalaria glabrata and Biomphalaria straminea are the two intermediate hosts most important in disease transmission (9) .…”