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Keywords

ehrlichiosis, ticks, canine, ehrlichia, prevalence

Abstract

Canine ehrlichiosis is a common disease seen in dogs. The southeastern United States has been identified as an area of high prevalence, including Arkansas. Changes in climate, household income, and tick population are factors contributing to high prevalence. Canine ehrlichiosis is caused by three Ehrlichia spp., which are E. canis, E. ewingii, and E. chaffeensis. Ticks transmit the pathogen, specifically Rhipicephalus sanguineus, Dermacentor variabilis, and Amblyomma americanum. For this study, the goal was to determine the prevalence of Ehrlichia spp. in Arkansas that causes canine ehrlichiosis. Ticks were collected from host canines and environmental locations. Ticks were identified by sex, species, and stage and tested using quantitative polymerase chain reaction (qPCR). If positive, Sanger sequencing was used to identify the Ehrlichia spp. carried by the tick. SNAP 4DX data were recorded at two Arkansas veterinary clinics to determine prevalence in dogs. Amongst the collected ticks, five species were found. Only D. variabilis and A. americanum were tested, as they were known Ehrlichia spp. vectors. Only A. americanum ticks were identified as carriers through Sanger sequencing, and, out of the A. americanum population, 1.84% 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, and data collected from the second clinic showed that 22.41% were positive in 2024. This study supports previous studies showing that Arkansas is an area of high prevalence.

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