Interventions can shift the thermal optimum for parasitic disease transmission

• Type of Material: Article
• Authors: Karena H Nguyen, Emory University; Philip H Boersch-Supan, British Trust for Ornithology, Thetford; Rachel B Hartman, Emory University; Sandra Y Mendiola, Emory University; Valerie J Harwood, University of South Florida, Tampa; David Civitello, Emory University; Jason R Rohr, University of Notre Dame
• Language: English
• Date: 2021-03-16
• Publisher: PNAS
• Publication Version: Final Published Version
• Copyright Statement: © 2021. Published under the PNAS license.
• Final Published Version (URL): http://dx.doi.org/10.1073/pnas.2017537118
• Title of Journal or Parent Work: Proceedings of the National Academy of Sciences of the United States of America
• Volume: 118
• Issue: 11
• Grant/Funding Information: Funds for the project were also provided to D.J.C. from the NIH (R01 AI150774-01).; This research was supported in part by the Porter Family Foundation awarded to K.H.N. Funds for the project were provided by grants to J.R.R. from the NSF (EF-1241889), the NIH (R01TW010286), and the US Department of Agriculture (2009-35102-0543). P.H.B.-S. was partially supported by NSF Grant PLR‐1341649. Computations for this study used JASMIN, the United Kingdom’s collaborative data analysis environment (https://jasmin.ac.uk/).
• Keywords: Schistosoma mansoni; Schistosomiasis mansoni; Humans; Animals; Temperature; temperature; climate change; epidemiological modeling; Host-Parasite Interactions; snail control; neglected tropical disease; Biomphalaria

Abstract

Temperature constrains the transmission of many pathogens. Interventions that target temperature-sensitive life stages, such as vector controlmeasures that kill intermediate hosts, could shift the thermal optimum of transmission, thereby altering seasonal disease dynamics and rendering interventions less effective at certain times of the year and with global climate change. To test these hypotheses, we integrated an epidemiological model of schistosomiasis with empirically determined temperature-dependent traits of the human parasite Schistosoma mansoni and its intermediate snail host (Biomphalaria spp.). We show that transmission risk peaks at 21.7 °C (Topt), and simulated interventions targeting snails and free-living parasite larvae increased Toptby up to 1.3 °C because interventionrelated mortality overrode thermal constraints on transmission. This Toptshift suggests that snail control is more effective at lower temperatures, and global climate change will increase schistosomiasis risk in regions that move closer to Topt. Considering regional transmission phenologies and timing of interventions when local conditions approach Toptwill maximize human health outcomes.