Contributions of hydrology to Vesicular Stomatitis Virus emergence in the western United States

Authors: Elias, Emile; McVey, David; Peters, Debra; Derner, Justin; PELZEL-MCCLUSKEY, ANGELA - Animal And Plant Health Inspection Service (APHIS); Schrader, Theodore - Scott; Rodriguez, Luis

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2018
Publication Date: 7/26/2018
Citation: Elias, E.H., McVey, D.S., Peters, D.C., Derner, J.D., Pelzel-McCluskey, A., Schrader, T.S., Rodriguez, L.L. 2018. Contributions of hydrology to Vesicular Stomatitis Virus emergence in the western United States. Ecosystems. 22:416-433. https://doi.org/10.1007/s10021-018-0278-5.
DOI: https://doi.org/10.1007/s10021-018-0278-5

Interpretive Summary: This submission is centered on investigating VSV transmission from a hydrologic perspective. As a vector-borne virus, the relationship with disease vectors (black flies and sand flies) is critically important. However, vector data are limited or unavailable, so we utilized hydrologic information and a watershed perspective to evaluate premises housing VSV infected horses between 2004 and 2016. The major findings of this research could support future biological investigation and management actions to minimize infection. Namely, we found that premises confirmed positive for VSV were near flowing water (with 72% within 1 km of lotic habitat). We also found that incidents occurred primarily after local streams returned to baseflow conditions. Habitat modeling revealed that in most watersheds, infected premises were associated with warmer temperatures, less precipitation, greener vegetation, wetter soils and more horses that the long-term background watershed.

Technical Abstract: Relationships between environmental variables associated with the spread of vector-borne pathogens, such as RNA viruses transmitted to humans and animals, remain poorly understood. Vesicular stomatitis (VS) is caused by a vector-borne, zoonotic RNA virus (VSV), and is the most common vesicular disease affecting livestock (domestic horses, cattle, pigs) throughout the Americas. This investigation focused on explaining patterns of >1500 incidents of VS in livestock in the western US from 2004-2016 related to the ecology of the host-vector-virus-environment system. We investigated the relationship between VS incidents and habitat characteristics expected to be important to insect vectors: stream location, streamflow conditions, climate, and vegetation. Results show that VS incidents were distributed near the stream network with 72% located within 1 km of lotic habitat. The watershed with highest number of VS confirmed premises had the largest mean premises distance from flowing water. Monthly incidents were closest to lotic habitat in April (x=525m) and furthest from lotic habitat in November, December and January (1,843m, 2,141n and 4,807m) indicating that initial infection near streams may spread away from these locations. All first incidents (n=35) occurred following peak annual streamflow, with 89% (31 of 35) of these occurring after streams returned to baseflow. This finding indicated that surveillance for VS could be targeted spatially in locally-relevant geographical areas (i.e., near streams) and temporally relative to local streamflow conditions which can be remotely monitored via existing web-accessible information networks. Habitat modeling of 11 subwatersheds revealed somewhat different models for each watershed with several factors important in multiple watersheds such as higher horse density. In nine of the 11 watersheds, the highest model PC (31 to 71%) represented either higher than average long-term mean temperature or lower than average long-term mean precipitation. Approaching habitat modeling on a watershed basis reveals information to support additional research. These spatial and temporal relationships showcase the importance of hydrological contributions to the emergence and distribution of an arthropod-borne disease in the western U.S.