Mammalian Assemblage Structure and Host-use Patterns of the Black-legged Tick (Ixodes scapulars) Across Anthropogenic Disturbances in East Texas




Westrich, Bradford J.

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Borrelia burgdorferi, the causative agent of Lyme disease, is responsible for infecting more than 300,000 people annually in the United States (US), with 95% of cases reported in the Northeastern US. However, human risk for contracting Lyme disease in Texas is much lower, with only 54 cases reported in 2015. Understanding the composition of mammalian reservoir host assemblages is commonly used to predict areas of greatest concern for human risk of Lyme disease. Community dynamic factors such as predation and competition greatly influence the composition of hosts present at any given time; however, anthropogenically-disturbed habitats are positively correlated to increased densities of highly competent B. burgdorferi reservoirs and vectors. My research objectives were to 1) assess if mammal assemblages differed across habitat disturbances; 2) determine if tick intensities were greater in disturbed habitats; 3) assess host-use patterns of tick vectors across East Texas; and 4) identify whether known vectors are associated with competent reservoirs of B. burgdorferi. I found that mammalian assemblages share high degrees of richness and evenness (Hurlbert’s PIE = 0.77 – 0.84), although disturbed habitats have greater proportions of rare species comprising 26 – 39% of assemblages. Average individual tick intensity differed across ecoregions in sylvan habitats with 634 ticks collected from mammals at Gus Engeling Wildlife Management Area (GEWMA) and 159 ticks collected from mammals at Big Thicket National Preserve (BTNP). I suspect this difference to be the result of a 13% increase in meso-mammal species with greater tick intensities captured at GEWMA. Furthermore, host-use patterns were observed for all Ixodes scapularis adults utilizing meso-mammal hosts and approximately 99% of Dermacentor variabilis nymphs selecting small mammal hosts. These results indicate that across evenly distributed mammalian assemblages in East Texas the prevalence of B. burgdorferi is expected to be low due to the rarity of competent reservoirs and association of known vectors with poor tick hosts.



Texas, Lyme disease, Mammal, Assemblage, Ixodes scapulars, Disease ecology


Westrich, B. J. (2017). <i>Mammalian assemblage structure and host-use patterns of the black-legged tick (Ixodes scapulars) across anthropogenic disturbances in East Texas</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


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