The role of birds as hosts for ticks, vectors of Borrelia burgdorferi, in eastern Texas
Gold, Brian D.
The bacterial spirochete Borrelia burgdorferi, the etiological agent of Lyme disease, an emerging infectious disease in the United States [US], has been detected in previous surveys in Texas. However, the northeastern and midwestern US are currently the areas with the highest abundance of cases of Lyme disease reported. Ticks of the genus Ixodes that are infected with Borrelia are solely responsible for transmission to humans, though humans are not components of the enzootic life cycle of Borrelia. The distribution of the black-legged tick, Ixodes scapularis, the primary vector of Borrelia to humans in the US includes most of the eastern portion of Texas. While adult I. scapularis ticks feed primarily on large mammals (e.g. deer), the larval and nymphal stages are generalists that will feed on numerous taxa, including small mammals, birds, and reptiles. This project, along with associated tick flagging, mammal, and reptile surveys in eastern Texas were implemented to ascertain how the Borrelia life cycle is structured at the local level in eastern Texas. The focus of my research was on the role that ground-dwelling and foraging birds had on the abundance and distribution of ticks in eastern Texas. The study sites chosen for this project were disturbed and more pristine sylvan habitats at Gus Engeling Wildlife Management Area [GEWMA] and Big Thicket National Preserve [BTNP]. A reference infestation rate of 5.1% was chosen to compare the observed infestation rate. In total, 211 birds were captured over two field seasons, 4 of which were found infested with Ixodes species ticks (1.9%). This suggests that birds are not an important vertebrate host group for maintaining tick density at the local level in eastern Texas. Several migratory bird species that have been found in other studies to be important in translocating ticks were captured at each site. A comparison of the alpha and beta diversity at and among each site revealed that the habitats at GEWMA were most similar in composition, though the disturbed habitat at BTNP was the most diverse (H’=2.4840). Ground-dwelling and foraging birds known to harbor I. scapularis were dominant species components of the avian assemblages at both GEWMA and BTNP. More research is needed to uncover which vertebrate host species are supporting the larval and nymphal stages of the I. scapularis population in eastern Texas.
Borrelia, Burgdorferi, Ticks, Texas
Gold, B. D. (2017). <i>The role of birds as hosts for ticks, vectors of Borrelia burgdorferi, in eastern Texas</i> (Unpublished thesis). Texas State University, San Marcos, Texas.