Spatiotemporal variability in transmission risk of human schistosomes and animal trematodes in a seasonally desiccating East African landscape

• Type of Material: Article
• Authors: Naima C Starkloff, Emory University; Teckla Angelo, National Institute of Medical Research Mwanza Center; Moses P Mahalila, National Institute of Medical Research Mwanza Center; Jenitha Charles, National Institute of Medical Research Mwanza Center; Safari Kinung-hi, National Institute of Medical Research Mwanza Center; David Civitello, Emory University
• Language: English
• Date: 2023-05-26
• Publisher: NIH
• Publication Version: Preprint (Prior to Peer Review)
• Copyright Statement: The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1101/2023.05.25.542103
• Title of Journal or Parent Work: bioRxiv
• Grant/Funding Information: N.C.S. and D.J.C. were supported by the US National Institute of Allergy and Infectious Diseases R01 AI50774-01. All fieldwork expenses were also funded by this source.
• Keywords: seasonality; aestivation; ephemerality; schistosomiasis; Schistosoma haematobium; Bulinus

Abstract

Different populations of hosts and parasites experience distinct seasonality in environmental factors, depending on local-scale biotic and abiotic factors. This can lead to highly heterogenous disease outcomes across host ranges. Variable seasonality characterizes urogenital schistosomiasis, a neglected tropical disease caused by parasitic trematodes (Schistosoma haematobium). Their intermediate hosts are aquatic Bulinus snails that are highly adapted to extreme rainfall seasonality, undergoing dormancy for up to seven months yearly. While Bulinus snails have a remarkable capacity for rebounding following dormancy, parasite survival within snails is greatly diminished. We conducted a year-round investigation of seasonal snail-schistosome dynamics in 109 ponds of variable ephemerality in Tanzania. First, we found that ponds have two synchronized peaks of schistosome infection prevalence and cercariae release, though of lower magnitude in the fully desiccating ponds than non-desiccating ponds. Second, we evaluated total yearly prevalence across a gradient of an ephemerality, finding ponds with intermediate ephemerality to have the highest infection rates. We also investigated dynamics of non-schistosome trematodes, which lacked synonymity with schistosome patterns. We found peak schistosome transmission risk at intermediate pond ephemerality, thus the impacts of anticipated increases in landscape desiccation could result in increases or decreases in transmission risk with global change.