Life-history traits indicate local adaptation of the schistosome parasite, Schistosoma mansoni, to its snail host, Biomphalaria pfeifferi.

The digenean trematode Schistosoma mansoni causes schistosomiasis (Bilharziasis), a significant human disease especially in sub-Saharan Africa. We tested local adaptation of this parasite to its intermediate host, the freshwater snail Biomphalaria pfeifferi, by exposure of S. mansoni to B. pfeifferi from one sympatric and four allopatric populations and measurement of life-history traits of both species over time. The pre-patent period, infection rate, and cercarial production of the parasite were determined, and the shell diameter, fecundity, and survival of the snail host were determined. The results provide evidence for local adaptation of S. mansoni to its sympatric snail host: the pre-patent period was the shortest, the cercarial production was moderate and accompanied by a higher survival rate, the growth was greater during the pre-patent period, and the fecundity was greater during the pre-patent period. The greater growth and fecundity of sympatric B. pfeifferi suggests the presence of growth and fecundity compensation. These fitness traits are relevant to energy allocation of the snail host and to the transmission strategy of the schistosome parasite.

[Thelohanellus bicornei n. sp. Myxosporidie (Myxosporea, Bivalvulida) a gill parasite of Labeo coubie Rüppel, 1832 (Osteichthyen, Cyprinidae) from Burkina Faso, West Africa]. / Thelohanellus bicornei n. sp. Myxosporidie (Myxosporea, Bivalvulida) parasite des branchies de Labeo coubie Rüppel, 1832 (Osteichthyen, Cyprinidae) au Burkina Faso, Afrique de l'Ouest.

Thelohanellus bicornei n. sp. (Myxosporea, Bivalvulida) is described from gill of Labeo coubie (Rüppel, 1832) (Osteichthyen, Cyprinidae) in Burkina Faso, West Africa. The cysts are small and their length is 150 to 350 microns. White, linked together they are rounded shape. The spores are ovoids with smooth valvar surface. Their posterior end is rounded and their anterior part shows two "horns like" expansions. Spores measured 13.5 +/- 0.56 (13-14) microns in length and 8.43 +/- 0.49 (8-9) microns in width. Horns length is 1 to 1.5 microns long. Polar capsule is piriform, it's length is 7.24 +/- 0.45 microns and the width 3.75 +/- 0.32 microns. The polar filament formed 10 turns.

Freshwater snail diversity in Benin (West Africa) with a focus on human schistosomiasis.

The aim of this study was to conduct a large-scale freshwater snail survey in Benin to assess the malacological diversity and the larval trematode infections with a focus on Schistosoma genus. We conducted 82 freshwater snail surveys in 35 sites ranked in 4 types and belonging to 9 out of 12 departments. Among 19,200 collected snails, 11 species of freshwater snails were identified. Four species of human schistosome transmitting snails, Bulinus forskalii, B. globosus, B. truncatus and Biomphalaria pfeifferi and seven species of non-human schistosome transmitting snails. Although B. forskalii and B. globosus were the most largely distributed snails, none of the Bulinus snails were found naturally infected by schistosomes. B. pfeifferi was found naturally infected by S. mansoni only in one site with a 0.56% prevalence. The most risky areas were Borgou and the four coastal departments. Preliminary contempory information on human schistosomiasis was provided from three different sites. Schistosoma haematobium was found with 57.1%, 96% and 100% prevalences (two of which were new records for this species in Benin) while S. mansoni was restricted to one site (Toho-Todougba) with 74.3% prevalence. Our data showed that both schistosomiasis haematobium and mansoni prevalences increased during the last nineteen years in Toho-Todougba site.