Apodemus agrarius is a potential natural host of severe fever with thrombocytopenia syndrome (SFTS)-causing novel bunyavirus

Abstract

Background: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne, novel bunyavirus-caused emerging infectious disease. It becomes a threat to public health due to its high fatality rate.

Objective: To clarify the epidemiological characteristics of SFTS and natural host(s) of SFTS-causing virus (SFTSV) in East China.

Study design: Serum antibody against SFTSV in 496 healthy villagers was examined by ELISA. SFTSV in acute sera of SFTS cases and lung tissues of house and field mouse/rats were identified using quantitative RT-PCR, cell culture, and sequencing.

Results: A total of 22 laboratory-confirmed SFTS cases were diagnosed between 2012 and 2014, of which 5 (22.7%) reported a history of tick-bites. The seroprevalance of SFTSV antibody was 10.5% in healthy villagers. SFTSV genomic RNAs were identified in 2 of 8 Apodemus agrarius but not in Rattus norvegicus (n=40) and Rattus losea (n=4). The 3 segments of SFTSV from 11 SFTS cases and 2 A. agrarius were successfully sequenced. Phylogenetic analyses indicated that at least 3 different SFTSV strains (inland-type, Ningbo-native-type, and their reassortant-type) were present in Ningbo. The 3 segments of the 2 SFTSV isolates from A. agrarius shared great sequence homologies to those isolated from the patients living in nearby villages.

Conclusion: The present study indicated that A. agrarius might be a natural host of SFTSV in East China.

Keywords: Apodemus agrarius; Evolution; Novel bunyavirus; Severe fever with thrombocytopenia syndrome; Tick.