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

Abstract

BackgroundTemperature 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 methodsUsing 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.ResultsThe 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.ConclusionThe 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.

Contextual and Psychosocial Factors Influencing the Use of Safe Water Sources: A Case of Madeya Village, uMkhanyakude District, South Africa

“…Our findings show that the Madeya community relies on surface water (unprotected dug wells, rivers and dams) as the main source of water for domestic use. This implies that the risk of contracting schistosomiasis infection from exposure to cercariae infested waters was high [33,34]. Previous studies in the same area reported high prevalence of schistosomiasis among school-going children [11,12].…”

A call for standardised snail ecological studies to support schistosomiasis risk assessment and snail control efforts

“…Therefore, medium sized snails are best suited to withstand desiccation on the soil surface because of a more favourable aperture size/weight ratio (Hira, 1968;Diaw et al, 1988). Secondly, humid soils offer better survival chances (Ohlweiler & Kawano, 2001;Kalinda et al, 2018a) although aerobic conditions remain a prerequisite (Chu et al, 1967a;Coles, 1969;Betterton, 1984;Ebele & Smith, 1990;Thomas & Daldorph, 1991). This explains why survival rates are lower in wet mud and places exposed to sunlight (Chu et al, 1967c;Hira, 1968;Van Aardt & Steytler, 2007) and why they increase when IH snails bury in moist mud (Chu et al, 1967a;Kalinda et al, 2018b).…”

The Effect of Climate Change and the Snail-Schistosome Cycle in Transmission and Bio-Control of Schistosomiasis in Sub-Saharan Africa

“…In contrast, Kalinda and co-workers [129] used data from laboratory and field experiments to develop a deterministic compartment simulation model for the life cycle of B. globosus. Their model generated fecundity of snail and survival rates similar to those in the laboratory.…”

“…It was also shown that there is decrease in number of both the snails and cercariae due to an increase in the environmental temperatures, with maximum reduction in abundance of snails by 14% and 27% and decrease in maximum cercariae by 8% and 17% when the temperatures were increased by 1 • C and 2 • C, respectively. Their findings suggested that a rise in future temperature due to climate change may alter the abundance of B. globosus and influence the prevalence of schistosomiasis [129].…”