Landscape dynamics of a vector-borne disease in the Western US: How vector-habitat relationships inform disease hotspots

Authors: Elias, Emile; Savoy, Heather; Swanson, Dustin; Cohnstaedt, Lee; Peters, Debra; Derner, Justin; PELZEL-MCCLUSKY, ANGELA - Texas A&M University; Drolet, Barbara; Rodriguez, Luis

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2022
Publication Date: 11/9/2022
Citation: Elias, E.H., Savoy, H.M., Swanson, D.A., Cohnstaedt, L.W., Peters, D.C., Derner, J.D., Pelzel-McClusky, A., Drolet, B.S., Rodriguez, L.L. 2022. Landscape dynamics of a vector-borne disease in the Western US: How vector-habitat relationships inform disease hotspots. Ecosphere. 13(11). Article e4267. https://doi.org/10.1002/ecs2.4267.
DOI: https://doi.org/10.1002/ecs2.4267

Interpretive Summary: We used habitat information to estimate the location of VSV vector at different outbreaks. We also looked for habitat characteristics that would suggest VSV hotspots. This effort could help in predicting likely VSV vector and resultant remidiation measures.

Technical Abstract: Vesicular stomatitis (VS) is a vector-borne viral disease causing lesions in livestock, quarantines at premises, county and state-levels and important economic losses. We investigated vector-habitat characteristics for vectors associated with VS in regions of recurrent disease within the western United States (US) that consistently lead to the environment where vector, host and pathogen populations intersect to enable pathogen transmission. We analyzed habitats for previously identified insect vectors, including black flies (S. vittatum complex), biting midges (C. variipennis complex, which includes Culicoides sonorensis), and sand flies (L. shannoni) in six regions of interest (ROI) containing hotspots of VS ranging from Texas to Wyoming. This analysis broadened understanding of (a) how regions of reoccurring VS differ from the broader western US, (b) how geographically separated regions and hotspots are similar across time, and (c) how vector-environment habitat a priori knowledge relates to observed hotspots. Analysis of watershed factors (livestock densities, land cover proportions, stream and lake densities, and irrigation methods) indicated a complex system separating areas with high, recurring VS from the broader western US. While no single characteristic separated the six ROI from other areas, we found two distinct emerging groups (northern ROI and TX). Hotspots, estimated from monthly VS concentrations, evolved northward throughout the year and most hotspots were closer to flowing water and agricultural land than the broader ROI. All ROIs contained environmental conditions suitable for multiple vectors at some point in the year, but black flies had highest suitability scores whereas biting midge scores were lower and varied annually with higher suitability in summer. Sand flies had the lowest suitability score in all ROIs consistent with their low likelihood of being vectors. Biting midge habitat patches were often orders of magnitude smaller than black fly patches, and hotspot patches reinforce the likelihood that BF may be the most critical vector in northern ROI, whereas both BM and BF have similar likelihood in southern ROI. Given limited existing vector data, this analysis provides an alternate pathway for using habitat information to estimate likely vectors responsible for transmission. Results could support early warning and mitigation efforts to reduce VS incidences.