Prevalence and egg surface morphology of capillariid nematodes in red foxes (Vulpes vulpes) from Hokkaido, Japan

Capillariid nematodes, such as Aonchotheca putorii, Eucoleus aerophilus, E. boehmi, and Pearsonema plica, parasitize canids. Reports about these nematodes parasitizing red foxes (Vulpes vulpes) in Japan are limited, and there are no prior records of E. boehmi. This study investigated 56 red foxes captured in Hokkaido and detected eggs of the four above species and Calodium hepaticum in rectal feces, with E. boehmi showing the highest prevalence (48%) as the first report in Japan. Low-vacuum scanning electron microscopy revealed distinct egg surface textures that support the current microscopical species identification keys. This study reveals that capillariids are prevalent in foxes in Hokkaido and the high prevalence of E. boehmi suggests a potential infection risk to domestic dogs.