Distribution, Seasonal Fluctuation and Infectivity of Schistosome Snail Hosts at Kiri Reservoir, Nigeria

Abstract

Kiri Lake, now over four decades old, has received limited scientific attention regarding its 
role in the transmission of water-related diseases. Recent reports, however, have linked 
schistosomiasis transmission in seven nearby communities to the lake, as its waters serve as 
the primary source for domestic use. In light of these concerns, this study investigated the 
distribution, seasonal population dynamics, and infection rates of freshwater snails, which act 
as intermediate hosts of schistosomes. Snails were sampled over a 20-month period using 
long-handled scoop nets at five strategically selected water contact sites. The study focused 
on species identification, seasonal population density, and infection prevalence. In addition, 
physicochemical parameters of lake water were analyzed, aquatic vegetation types were 
recorded, and human water contact activities were monitored throughout the study period. 
Three schistosome intermediate host snails were identified: Bulinus globosus, Bulinus 
truncatus, and Biomphalaria pfeifferi. The densities of B. globosus and B. pfeifferi peaked 
during the hot dry season but declined markedly during the rainy season. These seasonal 
variations were statistically significant within sites (p < 0.001), but not between sites (p > 
0.001). In contrast, B. truncatus populations showed little seasonal fluctuation. All three 
species were naturally infected with schistosomes. The seasonal infection trend mirrored 
that of uninfected snails, though differences in infection prevalence were not statistically 
significant (p > 0.001). The findings confirm that schistosomiasis is endemic in the Kiri Lake 
area and underscore the lake’s role as a persistent transmission focus. Control strategies 
should therefore adopt an integrated approach, combining snail population management, 
health education to reduce risky water contact behaviors, and provision of alternative potable 
water sources. Such interventions will be crucial to reducing disease burden and improving 
public health outcomes for the surrounding communities.