Epidemiological survey of severe fever with thrombocytopenia syndrome virus in ticks in Nagasaki, Japan

Abstract

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging disease that is endemic in East Asia. The SFTS virus (SFTSV) is transmitted to other organisms by infected ticks and is endemic to Nagasaki in western Japan. However, epidemiological information regarding SFTSV in Nagasaki ticks has not been elucidated. In this study, we first examined the sensitivities of SFTSV gene detection by real-time RT-PCR and virus isolation in cultured cells and mice. These methods could detect SFTSV in the samples containing more than 4 × 10⁰ ffu. Next, we attempted to isolate SFTSV and to detect viral gene in 2,222 nymph and adult ticks collected from May to August 2013 among seven regions of Nagasaki. However, neither virus isolation nor viral gene detection were confirmed in those tick pools. SFTSV positivity rates are considered very low in ticks and viral loads in ticks are also very limited. Further investigation by increasing the number of ticks and including larval samples in the investigation, as well as improved detection methods, may be required to find SFTSV-positive ticks in this region.