Investigation of Ticks and Tick-Borne Pathogens in Deciduous Forests of Eastern Central Alabama

Abstract

Ticks are obligate hematophagous arthropods, and as vectors of human disease, they are second only to mosquitoes in medical importance. There are many unknowns in Alabama regarding ticks and tick-borne diseases that require further study. In 2015, we sampled ticks across eight sites located in or near Auburn, AL, and investigated tick density, diversity and pathogen prevalence. Seven tick species were collected, but 97.71% of all samples were a single species, the lone star tick, Amblyomma americanum, the primary vector of ehrlichiosis. For prevalence studies, a multiplex qPCR assay was used to screen DNA samples from lone star ticks simultaneously for five pathogens. Our results revealed an absence of either Rickettsii parkeri or Panola Mountain Ehrlichia, but we did identify the presence of three bacterial species: R. amblyommii (54.51%), Ehrlichia chaffeensis (0.27%) and Ehrlichia ewingii (0.45%). Moreover, , we observed that questing ticks were unequally distributed within habitats. Thus, in 2016, we investigated factors that influence spatial variation of questing A. americanum within a single forested habitat. The hypothesis was tha questing behavior is driven by a combination of factors associated with microclimate, vegetation, and animal hosts. A stepwise Poisson regression model was used to examine these relationships. Our best-fit model included six explanatory factors: forest-floor gravimetric moisture, forest-floor depth, tree diversity, canopy cover, the number of available hosts, and weekly mean relative humidity.