Serological survey of severe fever with thrombocytopenia syndrome virus infection in Sika deer and rodents in Japan

Severe fever with thrombocytopenia syndrome (SFTS) is a newly recognized zoonosis that occurs in China, Japan, and South Korea and is caused by the SFTS virus (SFTSV), which is in the genus Phlebovirus, family Phenuiviridae. Since its discovery in Japan in 2013, SFTS has been reported in the western parts of the country. To elucidate the distribution of SFTSV, we conducted a serological survey of deer and rodents. Serum was screened using enzyme-linked immunosorbent assay (ELISA) and suspected cases were further tested with an indirect immunofluorescence antibody (IFA) assay. Serum samples from 315 deer from Hokkaido (non-endemic area), 41 deer from Miyazaki (endemic area), and 910 rodents from six locations in Japan were tested. Of the 41 deer from Miyazaki, 2 (4.9%) had high ELISA optical density (OD) values (0.1 < OD < 0.3) and a positive IFA result. All of the deer samples from Hokkaido were negative by ELISA (OD < 0.1). No SFTSV-positive rodents were found. Our results indicate that deer in Miyazaki were exposed to SFTSV, unlike deer from Hokkaido (P < 0.05).