Diversity of piroplasma species in small rodents and ticks captured in suburbs of Gifu City, central Japan.

Piroplasmas (Babesia and Theileria) are protozoa transmitted from ticks to warm-blooded animals. Some species of them, such as Babesia microti, can cause zoonotic infections. Although B. microti infections in wild rodents and ticks in Japan have been frequently reported in Hokkaido, there are only older reports of zoonotic babesiosis in other areas of Japan. In this study, we investigated prevalence of piroplasma species in wild rodents and ticks collected in near Gifu City, a central region in Japan, between 2021 and 2023 using nested-PCR to detect the 18S rRNA gene sequences of various piroplasma species. Among 87 wild rodents, piroplasma gene sequences detected in four large Japanese field mice (Apodemus speciosus) were 100% identical to B. microti Otsu/Hobetsu type. Notably, the gene detected in one pool of nymphal Haemaphysalis ticks was closely related to Babesia motasi-like isolates recently detected in human patients in South Korea. Additionally, the deer Theileria species, which has been widely detected throughout Asia, including Japan, was detected from Haemapyhsalis ticks. Our results indicate that a variety of piroplasmas, including piroplasmas that are potentially pathogenic to humans, such as B. microti Otsu/Hobetsu types and protozoa closely related to B. motasi, are distributed in the Gifu City area.