Molecular detection of prepatent Schistosoma mansoni infection in Biomphalaria glabrata snail vectors.

Approximately 240 million people worldwide are infected by Schistosoma. In Brazil, one of the main intermediate hosts of this parasite is Biomphalaria glabrata snails. The early detection of larval stages in intermediate hosts is an important challenge to public health, but it also represents an opportunity as a new alternative to indicate earlier natural infections before cercariae differentiation and emergence. In this context, we demonstrated that PCR amplification of a 28S gene fragment from the parasite does demonstrate S. mansoni infection in snails 14 days post infection. This conventional polymerase chain reaction amplified clear bands and was able to detect parasitic infection in the intermediate host B. glabrata under experimental conditions. However, we reinforce that this approach requires deeper investigations and further comparisons to confirm its specificity and sensitivity in earlier time points after miracidia infection. This approach has relevant potential as an effective molecular-based strategy for the monitoring of schistosomiasis transmission.

The current distribution pattern of Biomphalaria tenagophila and Biomphalaria straminea in the northern and southern regions of the coastal fluvial plain in the state of São Paulo

We analyze the current distribution of snails from genus Biomphalaria in the north and south of the coastal fluvial plain in the state of Sa˜o 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