Distribution pattern and diversity of Borrelia spp. detected from ticks in Niigata prefecture, Japan

Borreliosis is a tickborne disease caused by several species of Borrelia spirochete. In Japan, autochthonous cases are increasing in Hokkaido, and in the central Honshu, where Niigata is located. This study aimed to reckon the presence of Borrelia spp. in ticks and its epidemiological significance in Niigata prefecture.

From 41 sites of Niigata, 1,939 DNA samples from ticks were tested for the presence of Borrelia spp. by PCR. The spirochete was detected in 55 samples, resulting in a prevalence of 2.83% (55/1,939) overall. The DNA sequencing analysis revealed 3 species of Borrelia in Niigata prefecture, B. japonica 76.4% (42/55), B. miyamotoi 3.6% (2/55) and an unidentified Borrelia sp. 20% (11/55). Borrelia japonica was detected from adults of Ixodes ovatus, predominantly in females. Higher prevalence of B. japonica was found in Joetsu area, border with Nagano and Toyama prefectures. B. miyamotoi was detected in Chuetsu region, the central area of Niigata in adult females of I. ovatus. One type of Borrelia, identified to genus level, was detected in larvae, nymph and adult stages of Haemaphysalis spp. ticks mainly in Kaetsu, the northern region of the prefecture.