Spatiotemporal and seasonal transmission dynamics of Schistosoma haematobium and snail infectivity in Ase River catchment, Delta State, Nigeria

Abstract

Bulinus are intermediate snail hosts of Schistosoma haematobium. Despite their vectorial role, the transmission dynamics and infectivity of these intermediate snail hosts remain understudied in the Ase River. This longitudinal study evaluated the geospatial and seasonal transmission patterns and infectivity of three S. haematobium vectors between November 2020 and October 2022 in the Ase River catchment, Delta State, Nigeria. Eleven (11) geospatial water contact coordinates were mapped for monthly spatiotemporal collection of Bulinus species along the Ase River and its catchment, for two years. Snail sampling was performed for 45 minutes at each study site using scooping/hand-picking techniques and subsequently counted, identi ed, and recorded. Snails of the Bulinus genus were individually placed in a beaker containing distilled water and exposed to light to shed cercariae which were identi ed to be human schistosome type. The number of infected snails for each month and the season was also counted and recorded to establish spatiotemporal and seasonal infectivity transmission dynamics and infectivity. A total of 41.45% of the 2345 Bulinus snails collected were infected with S. haematobium. The monthly infectivity of Bulinus snails varied signi cantly (P < 0.05) throughout the study period (P = < 0.0001; F = 23.11; df = 11). Further analysis showed a strong signi cant association (χ2 = 23.57; df = 11; p = 0.015) between the study years. The Principal Component Analysis (PCA) also indicates that Bulinus infectivity in the Ase River catchment was primarily driven by February and January. B. truncatus consistently had the highest transmission potential, followed by B. globosus and B. senegalensis. ANOVA con rms that the monthly/study site infectivity and transmission potential in B. truncates, B. globosus and S. senegalensis were statistically, signi cant (P < 0.05). These results demonstrated a clear distinction in the patterns and relationships between the different months in terms of snail infectivity and seasonal transmission potential. This understanding will help in the continuous monitoring and targeted interventions to control schistosomiasis transmission in Ase River.