Reduced Susceptibility of a Biomphalaria tenagophila Population to Schistosoma mansoni after Introducing the Resistant Taim/RS Strain of B. tenagophila into Herivelton Martins Stream

Abstract

Studies performed in the last 30 years demonstrated that a strain of B. tenagophila from the Taim Biological Reserve is completely resistant to Schistosoma mansoni infection. This resistance to parasite infection is a dominant characteristic during crossbreeding with susceptible B. tenagophila strains. These experiments also identified a 350 bp molecular marker that is exclusive to the Taim strain and does not occur in other geographic strains of this snail species. The Taim strain (Taim/RS) of Biomphalaria tenagophila was bred on a large scale, physically marked and introduced into a stream in which previous malacological analyses had revealed the presence of only parasite-susceptible B. tenagophila. Samples of offspring captured 4, 11 and 14 months after the introduction of the Taim strain were examined, and the susceptibility of the snails to S. mansoni infection dropped from 38.6–26.5% to 2.1% during the 14 months after the introduction of the Taim snail strain. A significant correlation was also observed between the absence of infection and the identification of the Taim molecular marker. These results demonstrate that the genetic marker from the Taim strain was successfully introduced into the wild snail population. In addition, a significant relationship exists between the marker and resistance to infection.

Biomphalaria camerunensis as a viable alternative intermediate host for Schistosoma mansoni in southern Cameroon

“…A similar result was obtained by Simões et al [6] in populations of Biomphalaria taenagophila and B. straminea , intermediate hosts of S. mansoni in Brazil. However, the Petponoun population exhibited a relatively high susceptibility rate (21.9%), quite similar to that of other B. pfeifferi [10], B. glabrata (the main host of intestinal schistosomiasis in Brazil) [25] and B. taenagophila [26] populations. This result suggests that some B. camerunensis populations could be as susceptible to S. mansoni as their ‘appropriate’ intermediate hosts, contrary to the until now accepted idea that B. camerunensis is a poor host with almost no role in the transmission of S. mansoni .…”

“…Despite this high susceptibility, the significantly high mortality rate observed in infected individuals from Petponoun (Table 1) reflects the adverse effect of parasitic development on the survival of these infected individuals, and suggests that adaptation of the Petponoun population to S. mansoni from Nkolbisson is far from perfect. Since susceptibility to S. mansoni is easier to obtain over generations than resistance [26], and that an increase in temperature can induce the inversion of resistance to S. mansoni [27], the susceptibility of B. camerunensis populations to S. mansoni may increase as a consequence of global warming. Indeed, in Cameroon, the snail Bulinus camerunensis which has been formerly known to be resistant to S. haematobium strain of Barrombi-kotto is now susceptible to that strain [28].…”

The Susceptibility of <i>Biomphalaria</i> spp. from Mwea Irrigation Scheme in Kenya against <i>Schistosoma mansoni</i> Miracidia Infection

“…Breaking the life cycle of the parasites will offer an option to decrease transmission, by targeting intermediate host snails [15,16]. The use of genetically resistant snail vector to displace susceptible populations has been suggested [17,18]. The aim of this study therefore was to identify resistance and susceptible of vector snails populations in Kenya Mwea rice irrigation region.…”

Schistosomes and snails: a molecular encounter

“…Indeed, in a proof of concept study conducted in the Caribbean Island of St Lucia, the snail Biomphalaria straminae a secondary host of the parasite S. mansoni , not its compatible snail B. glabrata, was utilized to eliminate schistosomiasis in the part of the island where this form of control was adopted (Pointier, 1993). In a more recent Brazilian study, the introduction of parasite resistant strains of B. tenagophila into an endemic site was found to reduce transmission as cross hybridization between resident susceptible and introduced snails increased over time (De Almeida Marques et al, 2014). This alternative intervention method, focusing on reducing schistosomiasis by blocking the snail stage of the parasite life cycle although attractive, will require a better understanding of the molecular basis of the snail and parasite interaction.…”