Molecular detection of severe fever with thrombocytopenia syndrome and tick-borne encephalitis viruses in ixodid ticks collected from vegetation, Republic of Korea, 2014

Abstract

Ticks play an important role in transmission of arboviruses responsible for emerging infectious diseases, and have a significant impact on human, veterinary, and wildlife health. In the Republic of Korea (ROK), little is known about information regarding the presence of tick-borne viruses and their vectors. A total of 21,158 ticks belonging to 3 genera and 6 species collected at 6 provinces and 4 metropolitan areas in the ROK from March to October 2014 were assayed for selected tick-borne pathogens. Haemaphysalis longicornis (n=17,570) was the most numerously collected, followed by Haemaphysalis flava (n=3317), Ixodes nipponensis (n=249), Amblyomma testudinarium (n=11), Haemaphysalis phasiana (n=8), and Ixodes turdus (n=3). Ticks were pooled (adults 1-5, nymphs 1-30, and larvae 1-50) and tested by one-step reverse transcription polymerase chain reaction (RT-PCR) or nested RT-PCR for the detection of severe fever with thrombocytopenia virus (SFTSV), tick-borne encephalitis virus (TBEV), Powassan virus (POWV), Omsk hemorrhagic fever virus (OHFV), and Langat virus (LGTV). The overall maximum likelihood estimation (MLE) [estimated numbers of viral RNA positive ticks/1000 ticks] for SFTSV and TBEV was 0.95 and 0.43, respectively, while, all pools were negative for POWV, OHFV, and LGTV. The purpose of this study was to determine the prevalence of SFTSV, TBEV, POWV, OHFV, and LGTV in ixodid ticks collected from vegetation in the ROK to aid our understanding of the epidemiology of tick-borne viral diseases. Results from this study emphasize the need for continuous tick-based arbovirus surveillance to monitor the emergence of tick-borne diseases in the ROK.

Four Year Surveillance of the Vector Hard Ticks for SFTS, Ganghwa-do, Republic of Korea

“…nipponensis was too low to be considered vector for SFTS in our study sites. This prevalence shows a finding coincident with many studies in Korea [12,26,27,30]. The nymphal hard ticks were collected 4,137 individuals (23.70%), the females were 3,389 (19.41%), and the males were 1,654 (9.47%) and larvae were 8,277 (47.41%).…”

“…RT-qPCR assays were conducted using DiaStar TM 2X OneStep RT-PCR pre-mix (SolGent Co. Daejeon, Korea) in accordance with the manufacturer's protocol. The SFTS virus-specific primers used were as follows: MF3 (Sense) 5′-GATGAGATGGTCCATGCTGATTCT-3′ and MR2 (Anti-sense) 5′-CTCATGGGGTGGAATGTCCTCAC-3′ for the medium (M) segment of SFTS virus [26,27], and Actin L (Sense) 5′ -AGATCATGTTCGAGACCTTC-3′ and Actin R (Anti-sense) 5′ -TCAGGATCTTCATCAGGTAA-3′ for β-actin. RT-qPCR was performed using 15 μl 2X OneStep RT-PCR Pre-mix, each with 10 pmole primer, and 1 pg to 100 ng total RNA in a 30 μl total reaction volume.…”

Ixodes nipponensis Kitaoka and Saito and Amblyomma testudinarium Koch (Acari: Ixodida: Ixodidae) Collected from Reptiles (lizards, skinks, and snakes) in the Republic of Korea, 2016

“…This difference was due, in part, to the high numbers of I. nipponensis larvae (20 larvae) collected from Eremias argus in mid-June. However, in previous studies the number of I. nipponensis larvae increased in July, peaked in August, and then declined in September , Coburn et al 2016, Suh et al 2016 (Table 1).…”

“…In Korea, A. testudinarium was infrequently collected by tick drag or from small mammals (>2,500 rodents and soricomorphs) during a comprehensive survey in various habitats, perhaps in part because of its biting behavior and preference for larger mammals (Yamaguti et al 1971, 2014a, Coburn et al 2016, Johnson et al 2017.…”

Ornithodoros sawaii (Acari: Ixodida: Argasidae) collected from nest soil/litter of Synthliboramphus antiquus, Synthliboramphus wumizusume, and nest soil/litter and nestlings of Hydrobates monorhis on Gugul and Sogugul Islands, Jeollanam Province, Republic of Korea

“…In the Republic of Korea (ROK), tick-borne pathogenic bacteria [e.g., Ehrlichia and Anaplasma (Chae et al 2003, Kang et al 2013, Bartonella (Kim et al 2005, Kang et al 2013, Borrelia (Park et al 1992, Kee et al 1994, and Rickettsia spp. (Jang et al 2004, Noh et al 2017] and viruses [e.g., tick-borne encephalitis (Kim et al 2009b, Ko et al 2010) and severe fever with thrombocytopenia syndrome (SFTS) , 2016] manifest varying degrees of disease nationwide.…”