Low Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus Antibodies in Individuals Living in an Endemic Area in Japan.

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne infection with a high mortality rate. It is caused by the SFTS virus (SFTSV) and is endemic in some areas in western Japan, including the Kagoshima prefecture. In the present study, healthy individuals living in this prefecture were examined to assess for anti-SFTSV seroprevalence. An initial study was performed using the serum samples collected from a total of 646 individuals living in Kagoshima. At the same time, a questionnaire was used to collect information (such as occupation and a history of tick bite). Enzyme-linked immunosorbent assay and indirect immunofluorescence assay were used for the screening. Finally, the seroprevalence of anti-SFTSV antibodies was confirmed using a neutralization assay. Only 2 (0.3%) out of 646 study participants were positive for anti-SFTSV antibodies. No significant difference was observed between individuals who are at a high or low risk of tick bite in terms of seropositivity. Next, a total of 1,000 serum samples collected from general blood donors by the Japanese Red Cross Kyushu Block Blood Center were tested. None of these samples tested positive for anti-SFTSV antibodies. These results suggest a low seroprevalence of anti-SFTSV antibodies in healthy individuals living in an endemic area in Japan.

Detection and molecular characterization of Babesia, Theileria, and Hepatozoon species in hard ticks collected from Kagoshima, the southern region in Japan.

To reveal the distribution of tick-borne parasites, we established a novel nested polymerase chain reaction (PCR) system to detect the most common agents of tick-borne parasitic diseases, namely Babesia, Theileria, and Hepatozoon parasites. We collected host-seeking or animal-feeding ticks in Kagoshima Prefecture, the southernmost region of Kyusyu Island in southwestern Japan. Twenty of the total of 776 tick samples displayed a specific band of the appropriate size (approximately 1.4-1.6kbp) for the 18S rRNA genes in the novel nested PCR (20/776: 2.58%). These PCR products have individual sequences of Babesia spp. (from 8 ticks), Theileria spp. (from 9 ticks: one tick sample including at least two Theileria spp. sequences), and Hepatozoon spp. (from 3 ticks). Phylogenetic analyses revealed that these sequences were close to those of undescribed Babesia spp. detected in feral raccoons in Japan (5 sequences; 3 sequences being identical), Babesia gibsoni-like parasites detected in pigs in China (3 sequences; all sequences being identical), Theileria spp. detected in sika deer in Japan and China (10 sequences; 2 sequences being identical), Hepatozoon canis (one sequence), and Hepatozoon spp. detected in Japanese martens in Japan (two sequences). In summary, we showed that various tick-borne parasites exist in Kagoshima, the southern region in Japan by using the novel nested PCR system. These including undescribed species such as Babesia gibsoni-like parasites previously detected in pigs in China. Importantly, our results revealed new combinations of ticks and protozoan parasites in southern Japan. The results of this study will aid in the recognition of potential parasitic animal diseases caused by tick-borne parasites.