Eco-epidemiological Study of Ixodidae at the Interface of Humans, Domestic Animals, and Wildlife in Eastern Central Alabama

Abstract

Ixodidae, the family of hard ticks, are obligatory hematophagous ectoparasites of vertebrates and efficient vectors of a wide variety of pathogens affecting wildlife, domestic livestock, companion animals and humans. Ticks and tick-borne diseases pose persistent and growing challenges to human and animal health worldwide, but there remains minimal research in Alabama on their phenology, host interactions and associated pathogens. To address this gap in knowledge, my overarching goal was to assess the interactions between ticks, hosts and their pathogens within the environment using a variety of sampling methods. Sampling methods included both opportunistic host-tick collection for assessing tick diversity and tick dragging as the primary method for investigating phenology. I sampled vertebrate populations for host-tick collection including raccoons (Procyon lotor), wild pigs (Sus scrofa), white-tailed deer (Odocoileus virginianus), and coyotes (Canis latranis). Environmental sampling took place across eight sites for approximately eight months while host-tick collection occurred opportunistically through collaboration with ongoing projects. Following collection, tick samples were identified by species and then screened for pathogens using molecular methods.

I documented the presence of six known tick species in Alabama including Amblyomma americanum, Amblyomma maculatum, Dermacentor albipictus, Dermacentor variabilis, Ixodes scapularis and Rhipicephalus sanguineus. One of the major findings of this study was that habitat and host availability influence the complex dynamics of tick populations, resulting in phenological differences across regions. These regional differences were strongly associated with habitat characteristics, as tick abundance was positively correlated with shaded, moist forests and negatively associated with open grassy fields. Following pathogen screening, the presence of babesiosis, ehrlichiosis, rickettsiosis and Heartland virus (HRTV) were detected in the samples. Because HRTV has only been detected once before in this region, these results indicate that ticks and their diseases may be expanding. The findings from this study can be used to address existing gaps in research and inform public health surveillance for tick-borne disease in Alabama.