Prevalence of tick-borne encephalitis virus in ticks from southern Korea

Abstract

The prevalence of tick-borne encephalitis virus (TBEV) in southern Korea was determined by collecting ticks using tick drags. A total of 4,077 of 6,788 ticks collected were pooled (649 pools) according to collection site, species, and developmental stage and assayed for TBEV. The TBEV protein E and NS5 gene fragments were detected using RT-nested PCR in six pools of nymphs collected from Jeju Island (2,491 ticks). The minimum field detection rates for TBEV were 0.17% and 0.14% for Haemaphysalis longicornis and Haemayphysalis. flava nymphs, respectively. The 252 bp NS5 and 477 bp protein E gene amplicons were sequenced. Phylogenetic analysis showed that the NS5 and protein E genes of the Jeju strain were clustered with Western subtype (98.0% and 99.4% identity, respectively). The Western subtype of TBEV is endemic in Korea, including Jeju Island. The study of vector and zoonotic host susceptibility to TBEV is required to better understand its potential impact on public health.

Fig. 1

Distribution of tick collection sites (#1~113) with open circles (○) representing sites negative for TBEV and closed circles (•) representing sites positive for TBEV ticks [Positive collection sites: #25 (N 33° 31' 30.47", E 126° 35' 49.27", Jeju-si, Jeju Island), #46 (N 33° 25' 04.84", E 26° 37' 48.07", Jocheon-eup, Bukjeju-gun, Jeju Island), #52 (N 33° 20' 24.32", E 126° 42' 21.13", Namwon-eup, Namjeju-gun, Jeju Island), #65 (N 33° 26' 09.89", E 126° 29' 20.72", Jeju-si, Jeju Island), #68 (N 33° 25' 39.22", E 126° 29' 38.40", Mt. Halla, Jeju Island)].

Fig. 2

Alignment of the NS5 gene sequence from positive tick samples with available TBEV genetic information. Western subtype strains are highlighted in dark gray and Far Eastern subtype strains are highlighted in light gray.

Fig. 3

Phylogenetic tree showing the position of tick-borne encephalitis virus strain (JEJU) identified from Jeju Island, Korea.