Simulation of population dynamics of Bulinus globosus: Effects of environmental temperature on production of Schistosoma haematobium cercariae

Background: Temperature is an important factor that influences the biology and ecology of intermediate host (IH) snails and the schistosome parasites they transmit. Although temperature shifts due to climate change has been predicted to affect the life history traits of IH snails and parasite production, the mechanisms of how this may affect parasite abundance and disease risks are still not clear. Materials and methods: Using data from laboratory and field experiments, we developed a deterministic compartmental simulation model based on difference equations using a weekly time step that represented the life cycle of Bulinus globosus. We simulated snail population dynamics and the associated production of cercariae assuming current environmental temperatures as well as projected temperature increases of 1 °C and 2 °C. Results: The model generated snail fecundity and survival rates similar to those observed in the laboratory and also produced reasonable snail population dynamics under seasonally varying temperatures representative of generally favorable environmental conditions. Simulated relative abundances of both snails and cercariae decreased with increasing environmental temperatures, with maximum snail abundances decreased by 14% and 27%, and maximum cercariae productions decreased by 8% and 17%, when temperatures were increased by 1 °C and 2 °C, respectively. Conclusion: The results indicate that future rise in temperature due to climate change may alter the abundance of B. globosus and impact on the prevalence of schistosomiasis. Furthermore, increased temperatures may not linearly influence the abundance of S. haematobium. These results may have important implications for schistosomiasis control programmes in view of temperature driven changes in the life history traits of B. globosus and S. haematobium. Our study recommends that the use of deterministic models incorporating the effects of temperature on the life history traits of IH snails would be vital in understanding the potential impact of climate change on schistosomiasis incidences and prevalence. Author summary: The implementation of schistosomiasis control/elimination strategies depend on accurate estimations and predictions of the changes in the snail and parasite population. This is essential especially in the allocation of limited resources. The simulation model and the results presented here provide useful information on Bulinus globosus, the main intermediate host snail of Schistosoma haematobium in southern Africa. The predicted changes in the abundance of B. globosus and S. haematobium due to changes in temperature may be vital in the fight against schistosomiasis. The model predicts the current and future abundance of intermediate hosts snails by considering the future predicted temperature increases. These results may be useful in evaluating the snail-trematode interactions within the natural systems in which changes in the environmental conditions such a temperature may affect the population size of Bulinus globosus and disease incidences. These effects of temperature on B. globosus may play an important role in the implementation of snail control programmes.