Dissertation/Thesis Abstract

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Modeling Indirect Transmission Disease Risk: Anthrax in Bison in Southwestern Montana
by Nekorchuk, Dawn Michelle, Ph.D., University of Florida, 2017, 132; 13847487
Abstract (Summary)

The patterns of movement and space use by animals as they transverse landscapes can affect their chance of encountering pathogens in the environment, and therefore can alter their risk of disease transmission. This is particularly true when the pathogen can persist in the environment for long periods of time. One such disease, anthrax, caused by the bacterium Bacillus anthracis, is a worldwide zoonotic disease of concern.

The objectives of this research are to investigate bison space use in relation to risk of anthrax transmission, to develop guidelines on creation of resource selection functions, and to create a compartmental model of anthrax as an indirectly transmitted disease in bison to estimate the basic reproductive number which is a epidemiological metric. My study area was primarily based in a re-emerging anthrax disease system in southwestern Montana, where a multi-species anthrax outbreak event occurred on a ranch in 2008. No cases had been reported in this region in decades, however, positive serology results in later years suggest that there is continued exposure to Bacillus anthracis.

I investigated the movement patterns of the GPS-collared bison on this ranch using home-range estimators and subsequent analyses of the resulting polygons. I found individual variation in the potential risk of their home ranges, and a bison that exhibited serology results showing recent prior exposure to B. anthracis was the one with the riskiest patterns. A comparative study of variations in resource selection function (RSF) methods allowed for the development of general guidelines for the selection of available area given the movement patterns of the species. Species that have movements like central foragers or nomads benefit from using more broad area definitions like minimum convex polygons (MCP) while generating RSFs, while models built on territorial-like movements perform better with more modern and conservative methods such as localized convex hull (LoCoH) or potential path area (PPA). Finally, I created a model of anthrax in bison using an adaption of compartmental modeling systems to indirect disease transmission: (S)-Susceptible, (M)-Immune, (I)-Infected, (L)- Local infectious zone, (E)-Environment. I discovered that inclusion of a phenomenological factor to account for spatial aggregation improved model simulation behavior.

Indexing (document details)
Advisor: Blackburn, Jason K.
Commitee: Blackburn, Jason K., Fik, Tim, Liang, Song, Mao, Liang, Ryan, Sadie
School: University of Florida
Department: Geography
School Location: United States -- Florida
Source: DAI-B 80/07/(E), Dissertation Abstracts International
Subjects: Geography, Geographic information science, Epidemiology
Keywords: Anthrax, Bison, Compartmental model, Home range, Indirect disease transmission, Resource selection
Publication Number: 13847487
ISBN: 9780438947429
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