Date of Graduation
5-2025
Document Type
Thesis
Degree Name
Bachelor of Science in Agriculture
Degree Level
Undergraduate
Department
Animal Science
Advisor/Mentor
Loftin, Kelly
Committee Member
McDermott, Emily
Second Committee Member
Powell, Jeremy
Abstract
Canine ehrlichiosis is a disease that is commonly seen in dogs. In previous studies, the southeastern part of the United States has been identified as an area of high prevalence. Arkansas was included in the region where the prevalence is high. Changes in climate, household income, and tick population were identified as factors contributing to this high prevalence. Canine ehrlichiosis is caused by three Ehrlichia spp., which are E. canis, E. ewingii, and E. chaffeensis. Ticks are responsible for transmitting the disease, specifically R. sanguineus, D. variabilis, and A. americanum. For this study, the goal was to determine the prevalence of Ehrlichia spp. in Arkansas known to cause canine ehrlichiosis. Ticks were collected off host canines and from environmental locations frequented by dogs during the summer months. These ticks were identified by sex, species, and stage, and then they were pooled by location date and tested using quantitative polymerase chain reaction (qPCR). Individuals from positive pools were tested again using qPCR, and then, if positive, Sanger sequencing was used to identify what Ehrlichia spp. the tick was carrying. SNAP 4DX ehrlichiosis data was recorded at two veterinary clinics in Arkansas in order to determine prevalence in dogs. Amongst collected ticks, 88.4% were A. americanum, 7.5% were D. variabilis, 3.1% were A. maculatum, 0.8% were I. scapularis, and 0.2% were I. cookei. Only D. variabilis and A. americanum were included in testing, as they were tick species known to carry the three Ehrlichia spp. Only A. americanum ticks were identified as carriers through Sanger sequencing, and, out of the A. americanum population, 1.8% carried E. ewingii, 0.92% carried E. chaffeensis, and 0.92% carried Panola Mountain Ehrlichia. No co-infection or E. canis was found. In the SNAP 4DX testing, the first clinic showed 23.24% of tests were positive in 2023 and 22.12% in 2024. The data collected from the second clinic showed that the percentage of positive tests was 22.41% in 2024.
Keywords
tick; canine; ehrlichiosis; ehrlichia; prevalence; Arkansas
Citation
Berryhill, E. J. (2025). Assessing the prevalence of Ehrlichia spp. in ticks associated with canids in Arkansas. Animal Science Undergraduate Honors Theses Retrieved from https://scholarworks.uark.edu/anscuht/69
