Serological and molecular survey of tick-borne zoonotic pathogens including severe fever with thrombocytopenia syndrome virus in wild boars in Miyazaki Prefecture, Japan

Background: Miyazaki Prefecture is one of the hotspots of severe fever with thrombocytopenia syndrome (SFTS) cases and related deaths in Japan since 2013 and other pathogens of tick-borne diseases (TBDs). Japanese spotted fever and scrub typhus are also endemic in this region. Objectives: A total of 105 wild boars, hunted in 2009, were serologically examined as sentinels for TBDs to indirectly demonstrate the potential hazard of ticks transmitting pathogens to humans in the studied area. Methods: The collected blood and spleens of the wild boars underwent serological and molecular tests for SFTSV, Rickettsia japonica (Rj) [antibody to spotted fever group rickettsiae (SFGR) were tested by using species-common antigen], and Orientia tsutsugamushi (Ot). Results: Seroprevalences of SFTSV, SFGR, and Ot were 41.9%, 29.5%, and 33.3%, respectively. SFTS viral RNA was identified in 7.6% of the sera, whereas DNA of Rj or Ot was not detected in any sample. In total, 43.8% of the boars possessed an infection history with SFTSV (viral gene and/or antibody). Of these, 23.8% had multiple-infection history with SFGR and/or Ot. Conclusions: The high prevalence of SFTSV in wild boars might reflect the high risk of exposure to the virus in the studied areas. In addition, SFTSV infection was significantly correlated with Ot infection, and so were SFGR infection and Ot infection, indicating that these pathogens have common factors for infection or transmission. These data caution of the higher risk of SFTSV infection in areas with reported cases of other TBDs.