Reclassification of Borrelia spp. Isolated in South Korea Using Multilocus Sequence Typing

Surveillance and Molecular Identification of Borrelia Species in Ticks Collected at U.S. Army Garrison Humphreys, Republic of Korea, 2018-2019

Tick-borne pathogens are contributing factors for the increased incidence of vector-borne diseases throughout the world, including Lyme borreliosis, one of the most prevalent spirochetes belonging to the Borrelia burgdorferi sensu lato group. The present study focused on the detection of Borrelia species from hard ticks collected at U.S. Army Garrison Humphreys, Republic of Korea (ROK), using molecular and genotypic analyses. Tick-borne disease surveillance was conducted from January to December, 2018-2019. A total of 24,281 ticks (2 genera and 5 species) were collected from road-killed Korean Water deer (KWD) and by tick drag. Haemaphysalis longicornis (92.0%) was the most commonly collected species, followed by Haemaphysalis flava (4.9%), Ixodes nipponensis (3.1%), Haemaphysalis phasiana (0.07%), and Haemaphysalis japonica (<0.01%). The ospA gene sequences of Borrelia afzelii were detected in 12/529 pools of I. nipponensis. Three and one pools were positive for B. afzelii and Borrelia miyamotoi, respectively, using the 16s rRNA gene. None of the pools of Haemaphysalis ticks collected from KWD or by tick drag were positive for Borrelia species. I. nipponensis was collected throughout the year from KWD and from February to November by tick drag, suggesting that they were active throughout the year, and expanding the risk period for acquiring Lyme borreliosis and Borrelia relapsing fever in the ROK. This study assessed disease risk factors associated with the prevalence of Lyme disease in ticks collected from KWD and by tick drag using molecular analysis. These results provide an understanding and awareness into the prevalence and molecular characteristics of Borrelia species in the ROK.

Geographical Distribution of Borrelia burgdorferi sensu lato in Ticks Collected from Wild Rodents in the Republic of Korea

Lyme disease is a tick-borne zoonotic disease caused by Borrelia burgdorferi sensu lato (s. l.) via transmission cycles involving competent tick vectors and vertebrate reservoirs. Here, we determined the prevalence and distribution of Borrelia genospecies in 738 ticks of at least three species from wild rodents in nine regions of the Republic of Korea (ROK). Ticks were analyzed using nested PCR targeting partial flagellin B gene sequences, followed by sequence analysis. The prevalence of Borrelia infection was 33.6%, and the most common genospecies were B. afzelii (62.5%), B. valaisiana (31.9%), B. yangtzensis (2.4%), B. garinii (1.6%), and B. tanukii (1.6%). Borrelia afzelii was found in all regions except Jeju Island; this predominant genospecies was found in the northern and central sampling regions. Borrelia valaisiana, B. yangtzensis, and B. tanukii were found only in the southern regions with B. valaisiana being the most common, whereas B. yangtzensis and B. tanukii were only found on Jeju Island. Our study is the first to describe the nationwide prevalence of B. burgdorferi s. l. in ticks from wild rodents in the ROK. Continuous surveillance in ticks, animals, humans, and different regions is required to avoid disease distribution and possible transmission to humans in the ROK.

Molecular Detection and Characterization of Borrelia garinii (Spirochaetales: Borreliaceae) in Ixodes nipponensis (Ixodida: Ixodidae) Parasitizing a Dog in Korea

The present study aimed to detect and characterize Borrelia spp. in ticks attached to dogs in Korea. Overall, 562 ticks (276 pools) attached to dogs were collected and tested for Borrelia infection by PCR targeting the 5S-23S rRNA intergenic spacer region (rrf-rrl). One tick larva (pool level, 0.4%; individual level, 0.2%) was confirmed by sequencing Borrelia garinii, a zoonotic pathogen. For molecular characterization, the outer surface protein A (ospA) and flagellin genes were analyzed. Phylogenetic ospA analysis distinguished B. garinii from B. bavariensis, which has been recently identified as a novel Borrelia species. On the other hand, phylogenetic analysis showed that single gene analysis involving rrf-rrl or flagellin was not sufficient to differentiate B. garinii from B. bavariensis. In addition, the B. garinii-infected tick was identified as Ixodes nipponensis by sequencing according to mitochondrial 16S rRNA and the second transcribed spacer region. To our knowledge, this is the first study to report the molecular detection of B. garinii in I. nipponensis parasitizing a dog in Korea. Continuous monitoring of tick-borne pathogens in ticks attached to animals is required to avoid disease distribution and possible transmission to humans.