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.

The freshwater snail genus Bulinus plays a vital role in transmitting parasites of the Schistosoma haematobium group. A hybrid schistosome between S. haematobium and S. mattheei has been recently detected using DNA-based identification methods in school children along the Lake Malawi shoreline in Mangochi District. This finding raised the need for contemporary revaluation of local interactions between schistosomes and snails, with a particular focus on snail species within the Bulinus africanus group. In 2017 and 2018, malacological surveys sampled several freshwater sites in Mangochi District. Collected snails (n= 250) were characterised using cytochrome oxidase subunit 1 gene (cox1), with DNA barcoding of the ‘Folmer’ region and a rapid PCR-RFLP typing assay with double digestion with HaeIII and SacI restriction enzymes. DNA cox1 sequence analysis, with phylogenetic tree construction, suggested the presence of at least three Bu. africanus group taxa in Lake Malawi, Bu. globosus, alongside first reports of Bu. africanus and Bu. angolensis, which can be differentiated by PCR-RFLP methods. In addition, A total of 30 of the 106 Bu. africanus group snails (28.30%) were positive to the Schistosoma-specific screen using real-time PCR methods. This study provides new insight into the recent changes in the epidemiology of urogenital schistosomiasis as likely driven by a new diversity of Bu. africanus group snails within the lake