Exploring the Adaptation of Bulinus senegalensis and Bulinus umbilicatus to the Dry and Rainy Season in Ephemeral Pond in Niakhar (Senegal), an Area of Seasonal Transmission of Urogenital Schistosomiasis.

Bulinus snails surviving drought play a key role in seasonal transmission of urogenital schistosomiasis although our knowledge of their adaptation to dry season is still limited. We investigated the survival dynamic and infestation by Schistosoma haematobium of Bulinus snails during the dry and rainy seasons in a single pond in an area of seasonal schistosomiasis transmission in Senegal. Additionally, their aestivation capacity was evaluated under semi natural conditions. During the rainy season, of the 104 specimens collected, 98 (94.23%) and 06 (5.76%) were identified as B. senegalensis and B. umbilicatus, respectively. In the dry season, B. umbilicatus outnumbered B. senegalensis, however, all 5 (100%) B. senegalensis collected were viable and alive after interruption of aestivation by immersion in water while only 7 of 24 (29.16%) B. umbilicatus collected emerged from their dormant state. The adaptation of B. senegalensis and B. umbilicatus to the rainy and dry seasons, respectively, was also observed in semi-natural conditions. The rate of infestation with S. haeamatobium during the rainy season was 18.2% (19/104) while all the viable snails collected during the dry season were negative. B. senegalensis and B. umbilicatus have different seasonal dynamics with no evidence of maintaining S. haematobium infestation during the drought. Further studies including more survey sites and taking account both snails biology and ecological conditions are needed to better understand snail adaptation to seasonal changes and their ability to maintain S. haeamatobium infestation during drought.