Modeling the Combined Influence of Host Dispersal and Waterborne Fate and Transport on Pathogen Spread in Complex Landscapes

• Type of Material: Article
• Authors: Adam N. Akullian, University of Washington; Ding Lu, Sichuan Provincial Center for Disease Control and Prevention; Julia Z. McDowell, Emory University; George M. Davis, George Washington University; Robert C. Spear, University of California; Justin V Remais, Emory University
• Language: English
• Date: 2012-09-01
• Publisher: Springer Verlag (Germany)
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © Springer Science+Business Media B.V. 2012
• Final Published Version (URL): http://link.springer.com/article/10.1007%2Fs12403-012-0074-y
• Title of Journal or Parent Work: Water Quality, Exposure and Health
• ISSN: 1876-1658
• Volume: 4
• Issue: 3
• Start Page: 159
• End Page: 168
• Grant/Funding Information: This work was supported in part by the NSF/NIH Ecology of Infectious Disease Program (grant 0622743), by the National Institute for Allergy and Infectious Disease (grant nos. K01AI091864 and R01AI068854), and by the Emory University Global Health Institute Faculty Distinction Fund.
• Keywords: environment; Schistosoma japonicum; dispersal; fate and transport; public health; infectious disease; migration; spatial spread
• Research Categories: Health Sciences, Public Health; Health Sciences, Pathology; Environmental Sciences

Abstract

Environmental models, often applied to questions on the fate and transport of chemical hazards, have recently become important in tracing certain environmental pathogens to their upstream sources of contamination. These tools, such as first order decay models applied to contaminants in surface waters, offer promise for quantifying the fate and transport of pathogens with multiple environmental stages and/or multiple hosts, in addition to those pathogens whose environmental stages are entirely waterborne. Here we consider the fate and transport capabilities of the human schistosome Schistosoma japonicum, which exhibits two waterborne stages and is carried by an amphibious intermediate snail host. We present experimentally-derived dispersal estimates for the intermediate snail host and fate and transport estimates for the passive downstream diffusion of cercariae, the waterborne, human-infective parasite stage. Using a one dimensional advective transport model exhibiting first-order decay, we simulate the added spatial reach and relative increase in cercarial concentrations that dispersing snail hosts contribute to downstream sites. Simulation results suggest that snail dispersal can substantially increase the concentrations of cercariae reaching downstream locations, relative to no snail dispersal, effectively putting otherwise isolated downstream sites at increased risk of exposure to cercariae from upstream sources. The models developed here can be applied to other infectious diseases with multiple life-stages and hosts, and have important implications for targeted ecological control of disease spread.