Re-assessing thermal response of schistosomiasis transmission risk: Evidence for a higher thermal optimum than previously predicted

Citation

Aslan IH, Pourtois JD, Chamberlin AJ, Mitchell KR, Mari L, Lwiza KM, Wood CL, Mordecai EA, Yu A, Tuan R, Palasio RGS, Monteiro AMV, Little DC, Ozretich RW & Norman R (2024) Re-assessing thermal response of schistosomiasis transmission risk: Evidence for a higher thermal optimum than previously predicted. Coffeng LE (Editor) PLOS Neglected Tropical Diseases, 18 (6), Art. No.: e0011836. https://doi.org/10.1371/journal.pntd.0011836

Abstract
The geographical range of schistosomiasis is affected by the ecology of schistosome parasites and their obligate host snails, including their response to temperature. Previous models predicted schistosomiasis’ thermal optimum at 21.7°C, which is not compatible with the temperature in sub-Saharan Africa (SSA) regions where schistosomiasis is hyperendemic. We performed an extensive literature search for empirical data on the effect of temperature on physiological and epidemiological parameters regulating the free-living stages of S. mansoni and S. haematobium and their obligate host snails, i.e., Biomphalaria spp. and Bulinus spp., respectively. We derived nonlinear thermal responses fitted on these data to parameterize a mechanistic, process-based model of schistosomiasis. We then re-cast the basic reproduction number and the prevalence of schistosome infection as functions of temperature. We found that the thermal optima for transmission of S. mansoni and S. haematobium range between 23.1–27.3°C and 23.6–27.9°C (95% CI) respectively. We also found that the thermal optimum shifts toward higher temperatures as the human water contact rate increases with temperature. Our findings align with an extensive dataset of schistosomiasis prevalence in SSA. The refined nonlinear thermal-response model developed here suggests a more suitable current climate and a greater risk of increased transmission with future warming for more than half of the schistosomiasis suitable regions with mean annual temperature below the thermal optimum.

Notes
Additional authors: Devin Kirk; Tejas S. Athni; Susanne H. Sokolow; Eliezer K. N’Goran; Nana R. Diakite; Mamadou Ouattara; Marino Gatto; Renato Casagrandi; Fiona Allan; Andrew S. Brierley; Ping Liu,Thiago A. Pereira; Giulio A. De Leo

Journal
PLOS Neglected Tropical Diseases: Volume 18, Issue 6