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

Abstract

<i>Bulinus</i> snails surviving drought play a key role in the 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 the <i>Schistosoma haematobium</i> of <i>Bulinus</i> snails during the dry and rainy seasons in a single pond in an area of seasonal schistosomiasis transmission in Senegal. During the rainy season, 98 (94.23%) <i>B. senegalensis</i> and six (5.76%) <i>B. umbilicatus</i> were collected, respectively. In the dry season, <i>B. umbilicatus</i> outnumbered <i>B. senegalensis</i>, but all five (100%) <i>B. senegalensis</i> collected were viable and alive after the interruption of aestivation by immersion in water, while only 7 of 24 (29.16%) <i>B. umbilicatus</i> collected emerged from their dormant state. The rate of infestation with <i>S. haeamatobium</i> during the rainy season was 18.2% (19/104), while all the viable snails collected during the dry season were negative. <i>B. senegalensis</i> and <i>B. umbilicatus</i> have different seasonal dynamics with no evidence of maintaining <i>S. haematobium</i> 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 <i>S. haeamatobium</i> infestation during drought.