Neste trabalho analisamos a distribuição atual de caramujos do gênero Biomphalaria nos setores norte e sul da planície fluvial da costa litorânea de São Paulo. A região está inserida numa extensa planície costeira inundável. Os dados de 29 sítios de coletas confirmam que a coleção de água doce em ambos os setores é colonizada por Biomphalaria tenagophila e Biompalaria straminea. Ambas as espécies são hospedeiras intermediárias naturais do Schistosoma mansoni. A abundânciade B. straminea em sítios de coleta em que foram registrados recentemente apenas B. tenagophila, indica o potencial de expansão de B. straminea na região. A análise quantitativa de espécimes/espécie demonstra que o crescimento local das populações de B. tenagophila ocorre em períodos de baixa pluviosidade. Há maior risco de dispersão das populações de B. tenagophila entre diferentes coleções de água em períodos úmidos, quando a alta pluviosidade promove a cheia dos principais rios e inundações decorrentes do escoamento de água da Serra do Mar para a planície costeira. O aumento da temperatura causada por alterações climáticas globais, e consequentemente o aumento de cheias e inundações, deve interferir na distribuição dos caramujos na planície fluvial do litoral, com risco de alteração na transmissão autóctone da esquistossomose nesta região.

We analyze the current distribution of snails from genus Biomphalaria in the north and south of the coastal fluvial plain in the state of São Paulo, which is part of a large coastal floodplain. Data from twenty-nine collection sites confirmed that the freshwater body in both regions is colonized by Biomphalaria tenagophila and Biomphalaria straminea, which are natural intermediate hosts of Schistosoma mansoni. The abundance of B. straminea in collection sites where only B. tenagophila had previously been recorded indicates the potential for B. straminea to expand in the region. While quantitative analysis of the number of specimens per species showed that local growth of B. tenagophila populations occurs during periods with little rainfall, there is a greater risk of B. tenagophila populations spreading between different water bodies during rainy periods, when heavy rainfall results in water levels rising in the main rivers and flooding caused by water flowing from the Serra do Mar mountain range to the coastal plain. The temperature increase caused by global climate changes and the consequent increasing frequency of high-water levels and floods can be expected to affect the distribution of these snails on the coastal fluvial plain, leading to the risk of a change in the autochthonous transmission pattern of schistosomiasis in the region.

Introduction Human migration and the presence of natural vectors (mollusks) of Schistosoma mansoni are the primary causes of the expansion of mansoni schistosomiasis into southern areas of South America. Water conditions are favorable for the expansion of this disease because of the extensive hydrographic network, which includes the basins of the Paraná and Uruguay rivers and favors mollusk reproduction. These rivers also aid agriculture and tourism in the area. Despite these favorable conditions, natural infection by S. mansoni has not yet been reported in Argentina, Uruguay, or Paraguay. Methods Two species of planorbid from Argentina, Biomphalaria straminea and B. tenagophila, were exposed to the miracidia of five Brazilian strains of S. mansoni. Results Biomphalaria tenagophila (Atalaya, Buenos Aires province) was infected with the SJS strain (infection rate 3.3%), confirming the experimental susceptibility of this Argentinian species. Biomphalaria straminea (Rio Santa Lucía, Corrientes province) was susceptible to two Brazilian strains: SJS (infection rate 6.7%) and Sergipe (infection rate 6.7%). Conclusions These results demonstrate that species from Argentina have the potential to be natural hosts of S. mansoni and that the appearance of foci of mansoni schistosomiasis in Argentina is possible.