Eco-epidemiology of Fasciolosis and Schistosomiasis at the Human-Animal-Mollusc Interface in Lake Dang, Adamawa-Cameroon

Background: Fasciolosis and schistosomiasis are neglected tropical diseases (NTDs) responsible for waterborne diseases of animals and humans in Cameroon. Objective: Malacological and parasitological studies were conducted from August 2022 to February 2023 to determine the abundance, distribution, and diversity of molluscs in Lake Dang, and the risk of infestation of animals and humans. Methods: A total of 8 sampling stations were chosen. The collected molluscs were exposed to strong light to induce cercarial emission. The stools and urine of users near the lake were collected and microscopically analysed. Results: The average densities of collected molluscs varied significantly from 0 molluscs in stations 5, 6, 7, and 8 to 62 ± 59.26 molluscs in station 1 (P < 0.001). Lymnaea natalensis was the most abundant species (A =42.72%), followed by Biomphalaria pfeifferi (A = 28.36%) and Bulinus globosus (A = 25.52%), while Bulinus forskalii was very poorly represented (A = 3.40%) (P< 0.05). The overall prevalence of cercarial emission was 68.91%, varying significantly between 16.66% for Schistosoma sp in B. forskalii and 83.33% for Fasciola gigantica in L. natalensis (P < 0.05) and was highest for those of F. gigantica (83.33%) and S. haematobium (79.72%), and lower for B. forskalii (16.66%). This prevalence was higher during the hot (84.61%; 77.77%) and cold (61.62%; 71.42%) seasons for Schistosoma haematobium in B. globosus and S. mansoni in B. pfeifferi (P < 0.001), and in the hot dry season (84.61%) and rainy season (64.28%), while that of S. haematobium in B. globosus was higher (P < 0.001). The distribution of L. natalensis populations was related to pastoral activity areas (P < 0.05), while those of B. globosus and B. pfeifferi were related to human activity areas in pastures (P < 0.05). Conclusion: Lake Dang is a breeding ground that promotes the endemicity of fasciolosis and human schistosomiasis.