First description of Hepatozoon canis in raccoon dog (Nyctereutes procyonoides)

Abstract

Hepatozoon canis is a tick-borne apicomplexan parasite that primarily infects domestic and wild canids. While its presence has been documented globally, previous studies have reported its absence in raccoon dogs (Nyctereutes procyonoides) in Europe, and its status in Asian populations remains unclear. This study presents the first molecular detection of H. canis in raccoon dogs in South Korea. Between 2021 and 2023, blood samples from 275 raccoon dogs admitted to 9 wildlife centers were analyzed using PCR targeting a partial sequence of the 18S rRNA gene. Overall, 21.5 % of samples tested positive, with the highest prevalence observed in the southern region (38.2 %) and the lowest in the north (8.8 %) in South Korea. Sequencing of amplicons revealed high similarity to H. canis found in a Japanese hard tick (Ixodes nipponensis) also from South Korea. Remarkably, the infection rate in raccoon dogs was significantly higher than previously reported in Korean domestic dogs (0.2–0.9 %) and ticks (0.09 %), indicating raccoon dogs may function as key sylvatic reservoirs. These findings suggest the possibility of alternative transmission pathways including predation or vertical transmission. Given the expanding raccoon dog population and thus increasing contact with domestic animals and shared habitats, their role in the ecology of H. canis and other tick-borne pathogens merits attention. This study underscores the importance of wildlife disease surveillance within the One Health framework and highlights the need for further research into host–vector dynamics and potential spillover risks at the wildlife–domestic animal interface.