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

Seasonal Dynamics of Ticks and Tick-Borne Pathogens in Republic of Korea

Tick-borne diseases are a public health problem and a significant burden on the livestock industry. The seasonal abundance of ticks and tick-borne pathogens strongly correlates with the prevalence of these diseases. To investigate the seasonal variation in ticks and tick-borne pathogens, ticks were collected from Gangwon State, Korea, and the tick-borne pathogens Borrelia, Anaplasma, Babesia, and Theileria were examined. In total, 14,748 ticks were collected, comprising ticks from two genera and three species: Haemaphysalis longicornis, Haemaphysalis flava, and Ixodes nipponensis, with H. longicornis being the predominant species. Of 7445 ticks (455 pools) examined for pathogens, Theileria was detected in 61 pools, whereas Borrelia and Anaplasma were observed in 17 pools. H. longicornis nymphs and adults were collected beginning in April, with nymph numbers peaking in May and June and adult ticks peaking in June and July. In contrast, the larvae were collected in May and peaked in September. Tick-borne pathogens were detected in April, peaking in July and September. Borrelia, the causative agent of Lyme disease, exhibits a temporal association between its detection in ticks and its occurrence in humans. In conclusion, tick-borne diseases seem to be closely linked not only to changes in tick numbers throughout the seasons but also to the seasonal variations of the pathogens within them.

An Updated Review on the Spatial Distribution of Borrelia burgdorferi Sensu Lato Across Ticks, Animals and Humans in Northeastern China and Adjacent Regions

BACKGROUND

Lyme disease is a tick-borne zoonotic disease caused by Borrelia burgdorferi sensu lato and is prevalent in northeastern Asia, particularly in the forested area of Northeastern China. However, a lack of systematic data on the spatial distribution of B. burgdorferi in this region hinders the prediction of its transmission risk across the landscape.

METHODS

To provide an updated overview and establish a comprehensive spatial distribution database, we conducted a systematic review of literature published between 2000 and 2022. We collected and compiled relevant data on B. burgdorferi in Northeastern China and its neighbouring regions, outlining its distribution in ticks, wild animals, livestock and humans. Spatial analysis was performed to identify spatial clusters of tick positivity and host infection rates.

RESULTS

From a total of 1823 literature, we selected 110 references to compile 626 detection records of B. burgdorferi, including 288 in ticks, 109 in wildlife, 111 in livestock and domestic animals and 100 in humans. The average detection rate of B. burgdorferi in ticks was approximately 20%, with wildlife, livestock and domestic animal host positivity rates below 50% and human seroprevalence rates varying from 0.94% to 44.18%.

CONCLUSIONS

The study identified the presence of 17 tick species and ten genotypes of B. burgdorferi in the region, indicating a broad distribution. Notably, B. burgdorferi exhibited notable clustering, particularly in the central and eastern areas of Jilin Province, warranting further investigation.

Molecular surveillance of zoonotic pathogens from wild rodents in the Republic of Korea

BACKGROUND

Rodents are recognized as major reservoirs of numerous zoonotic pathogens and are involved in the transmission and maintenance of infectious diseases. Furthermore, despite their importance, diseases transmitted by rodents have been neglected. To date, there have been limited epidemiological studies on rodents, and information regarding their involvement in infectious diseases in the Republic of Korea (ROK) is still scarce.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated rodent-borne pathogens using nested PCR/RT-PCR from 156 rodents including 151 Apodemus agrarius and 5 Rattus norvegicus from 27 regions in eight provinces across the ROK between March 2019 and November 2020. Spleen, kidney, and blood samples were used to detect Anaplasma phagocytophilum, Bartonella spp., Borrelia burgdorferi sensu lato group, Coxiella burnetii, Leptospira interrogans, and severe fever with thrombocytopenia syndrome virus (SFTSV). Of the 156 rodents, 73 (46.8%) were infected with Bartonella spp., 25 (16.0%) with C. burnetii, 24 (15.4%) with L. interrogans, 21 (13.5%) with A. phagocytophilum, 9 (5.8%) with SFTSV, and 5 (3.2%) with Borrelia afzelii. Co-infections with two and three pathogens were detected in 33 (21.1%) and 11 rodents (7.1%), respectively. A. phagocytophilum was detected in all regions, showing a widespread occurrence in the ROK. The infection rates of Bartonella spp. were 83.3% for B. grahamii and 16.7% for B. taylorii.

CONCLUSIONS/SIGNIFICANCE

To the best of our knowledge, this is the first report of C. burnetii and SFTSV infections in rodents in the ROK. This study also provides the first description of various rodent-borne pathogens through an extensive epidemiological survey in the ROK. These results suggest that rodents harbor various pathogens that pose a potential threat to public health in the ROK. Our findings provide useful information on the occurrence and distribution of zoonotic pathogens disseminated among rodents and emphasize the urgent need for rapid diagnosis, prevention, and control strategies for these zoonotic diseases.

Distribution and pathogen prevalence of field-collected ticks from south-western Korea: a study from 2019 to 2022

Hard ticks are known vectors of various pathogens, including the severe fever with thrombocytopenia syndrome virus, Rickettsia spp., Coxiella burnetii, Borrelia spp., Anaplasma phagocytophilum, and Ehrlichia spp. This study aims to investigate the distribution and prevalence of tick-borne pathogens in southwestern Korea from 2019 to 2022. A total of 13,280 ticks were collected during the study period, with H. longicornis accounting for 86.1% of the collected ticks. H. flava, I. nipponensis and A. testudinarium comprised 9.4%, 3.6%, and 0.8% of the ticks, respectively. Among 983 pools tested, Rickettsia spp. (216 pools, 1.6% MIR) were the most prevalent pathogens across all tick species, with R. japonica and R. monacensis frequently detected in I. nipponensis and Haemaphysalis spp., respectively. Borrelia spp. (28 pools, 0.2% MIR) were predominantly detected in I. nipponensis (27 pools, 13.8% MIR, P < 0.001). Co-infections, mainly involving Rickettsia monacensis and Borrelia afzelii, were detected in I. nipponensis. Notably, this study identified R. monacensis for the first time in A. testudinarium in South Korea. These findings offer valuable insights into the tick population and associated pathogens in the region, underscoring the importance of tick-borne disease surveillance and prevention measures.

Parasitic Characteristics of Ticks (Acari: Ixodidae) Collected from Water Deer (Hydropotes inermis argyropus) and Spatiotemporal Distribution Prediction within Host-Influenced Cultivated Areas

Tick-borne diseases result from human-ixodid tick encounters, making it crucial to understand host-ixodid tick interactions and host-dependent distribution for epidemiology and prevention. This study examines water deer patterns and ixodid tick interactions in designated croplands of South Korea over two years, finding that the highest deer presence occurred in July and the lowest in May, during crop harvesting. Four tick species were identified, with Haemaphysalis longicornis being predominant (92.2%). Tick life stage analysis revealed peak nymphs and adults in July and larvae in October. Nymph abundance correlated positively with nearby water deer. MaxEnt biodiversity prediction results indicated wider water deer distribution in summer, reflecting their tendency to use multiple croplands. Areas with nymphs and adults aligned with predicted deer presence in summer, while larval areas aligned in autumn. Increased agroforestry expanded water deer habitats, enhancing tick dispersion. Prevention involved minimizing human-deer encounters by strategic land use in tick-prone areas. This comprehensive study provides insights into preventing severe fever with thrombocytopenia syndrome in agricultural workers, emphasizing the need for targeted interventions based on host behavior and tick life stages in different seasons.

Serological investigation of seven zoonotic pathogens in companion dogs in South Korea, 2018-2021

Based on the current situation of Korean culture and society, the population of companion animals in South Korea is growing rapidly along with zoonotic risks. The current data regarding zoonotic infections in companion dogs reported in Korea is sparse. This study aims to investigate the seroprevalence of seven potential zoonotic pathogens in companion dogs in South Korea: Anaplasma phagocytophilum, Borrelia burgdoferi, Ehrlichia canis, Coxiella burnetii, Brucella canis, Leptospira spp. and canine influenza A virus. A total of 284 serum samples were collected from 2018 to 2021, and the immunoglobulin G (IgG) antibodies against 7 zoonotic pathogens were detected using enzyme-linked immunosorbent assays. Samples were divided into five groups and analysed based on age. IgG antibodies against six of the seven pathogens were detected. The highest seropositivity rate was detected for canine influenza A virus exposure (59.1%) for which the rates were the highest in dogs under 1 year old and declined with age. Positivity rates of the other pathogens were relatively low: 1.76% for Leptospira spp., 1.40% for A. phagocytophilum and E. canis, 1.06% for B. canis and 0.35% for B. burgdoferi. No antibodies against C. burnetii were detected in this study. The exposure of dogs in South Korea to six zoonotic pathogens was serologically confirmed, highlighting a potential risk for human infection. The zoonotic risk of companion dogs cannot be neglected, and implementation of One Health approach should be advocated to establish effective preventive measures.

Molecular Detection of Anaplasma, Ehrlichia and Rickettsia Pathogens in Ticks Collected from Humans in the Republic of Korea, 2021

Tick-borne pathogens (TBPs), transmitted by the bites of ticks, are of great medical and veterinary importance. They include bacteria, viruses, and protozoan parasites. To provide fundamental data on the risk of tick contact and public health strategies, we aimed to perform a molecular investigation on four tick-borne bacterial pathogens in ticks collected from humans across the Republic of Korea (ROK) in 2021. In total, 117 ticks were collected, including Haemaphysalis longicornis (56.4%), Amblyomma testudinarium (26.5%), Ixodes nipponensis (8.5%), H. flava (5.1%), and I. persulcatus (0.9%). Among the ticks, 20.5% (24/117) contained tick-borne bacterial pathogens, with infection rates of 17.9% for Rickettsia (Candidatus Rickettsia jingxinensis, R. tamurae, R. monacensis, and Candidatus Rickettsia tarasevichiae), 2.5% for Anaplasma (A. phagocytophilum, A. capra, and A. bovis), and 0.9% for Ehrlichia (Ehrlichia sp.). Additionally, the co-detection rate for R. monacensis and A. phagocytophilum was 0.9%. To our knowledge, this is the first report of A. capra and A. bovis detection in ticks collected from humans in the ROK. This study contributes to the understanding of the potential risk of tick contact and provides fundamental data for establishing a public health strategy for tick-borne disease management in the ROK.

Redox Imbalance and Its Metabolic Consequences in Tick-Borne Diseases

One of the growing global health problems are vector-borne diseases, including tick-borne diseases. The most common tick-borne diseases include Lyme disease, tick-borne encephalitis, human granulocytic anaplasmosis, and babesiosis. Taking into account the metabolic effects in the patient's body, tick-borne diseases are a significant problem from an epidemiological and clinical point of view. Inflammation and oxidative stress are key elements in the pathogenesis of infectious diseases, including tick-borne diseases. In consequence, this leads to oxidative modifications of the structure and function of phospholipids and proteins and results in qualitative and quantitative changes at the level of lipid mediators arising in both reactive oxygen species (ROS) and ROS enzyme-dependent reactions. These types of metabolic modifications affect the functioning of the cells and the host organism. Therefore, links between the severity of the disease state and redox imbalance and the level of phospholipid metabolites are being searched, hoping to find unambiguous diagnostic biomarkers. Assessment of molecular effects of oxidative stress may also enable the monitoring of the disease process and treatment efficacy.

Case Report: The First Borrelia yangtzensis Infection in a Human in Korea

Borrelia yangtzensis has been identified in rodents and ticks in China and Japan. A 57-year-old woman with bite mark was diagnosed with B. yangtzensis infection via molecular and serological testing. Here, we report the first case of human infection caused by B. yangtzensis in Korea.

The Role of Ticks in the Emergence of Borrelia burgdorferi as a Zoonotic Pathogen and Its Vector Control: A Global Systemic Review

Ticks are widely distributed across the globe, serving as hosts for numerous pathogens that make them major contributors to zoonotic parasitosis. Borrelia burgdorferi is a bacterial species that causes an emerging zoonotic tick-borne disease known as Lyme borreliosis. The role of ticks in the transmission of this pathogen was explored in this study. According to this systematic review, undertaken according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 19 tick species are known to carry Borrelia burgdorferi, with more than half of the recorded cases in the last two decades related to Ixodes ricinus and Ixodes scapularis ticks. Forty-six studies from four continents, Europe, North America, Asia, and Africa, reported this pathogen in ticks collected from vegetation, animals, and humans. This study highlights an increasing distribution of tick-associated Borrelia burgdorferi, likely driven by accelerated tick population increases in response to climate change coupled with tick dispersal via migratory birds. This updated catalogue helps in compiling all tick species responsible for the transmission of B. burgdorferi across the globe. Gaps in research exist on Borrelia burgdorferi in continents such as Asia and Africa, and in considering environmentally friendly vector control strategies in Europe and North America.

Molecular Identification of Borrelia spp. from Ticks in Pastures Nearby Livestock Farms in Korea

Simple Summary

Lyme borreliosis is caused by a spirochete from the Borrelia burgdorferi sensu lato group. Borrelia afzelii and B. garinii are known to be pathogenic to humans. The main vector for Lyme borreliosis is the Ixodes tick. In this study, Borrelia infection was confirmed in Ixodes,Haemaphysalis, and Amblyomma ticks. To our knowledge Borrelia infection was first confirmed in Amblyomma testudinarium in Korea. Based on phylogenetic analysis, all sequences were aligned with B. afzelii isolates and showed a close relationship with high identity. Considering that B. afzelii causes infectious zoonotic diseases, continuous monitoring and attention are still required (although a low prevalence was recorded in this study).

Abstract

Ticks are vectors that spread pathogenic bacteria, viruses, and protozoa. As the number of ticks increases due to climate change, the importance of the study of tick-borne pathogens has also increased. This study was conducted to investigate the distribution of the major tick species causing Lyme borreliosis and regional differences in the prevalence of Borrelia spp. by tick species. Borrelia infection was confirmed not only in Ixodes ticks, which are the major vectors of Borrelia spp., but also in Haemaphysalis and Amblyomma ticks. PCR targeting the 5S-23S rRNA intergenic spacer region (rrf-rrl) was performed to confirm Borrelia positivity. A total of 6102 ticks (736 pools) were tested, and the proportion was Haemaphysalis longicornis nymphs and adults at 69.2%, Haemaphysalis flava nymphs and adults at 13.9%, Haemaphysalis spp. larva at 14.3%, Ixodes nipponensis at 0.8%, and Amblyomma testudinarium at 1.9%. Ixodes nipponensis showed the highest minimum infection rate (MIR: 34.00; 17 pools/50 ticks) for Borrelia spp., followed by A. testudinarium (MIR: 0.88), and H. longicornis (MIR: 0.05). In particular, to our knowledge Borrelia infection was first confirmed in A. testudinarium in Korea. As a result of phylogenetic analysis, all sequences were grouped with Borreliaafzelii isolates and showed a close relationship with high identity. Considering that B. afzelii causes infectious zoonotic diseases, continuous monitoring and attention are needed, although it has a low prevalence in this study.

First report of Borrelia burgdorferi sensu stricto detection in a commune genospecies in Apodemus agrarius in Gwangju, South Korea

Lyme disease is a tick-borne infectious disease caused by the Borrelia burgdorferi sensu lato complex. However, the distribution of Borrelia genospecies and the tissue detection rate of Borrelia in wild rodents have rarely been investigated. Here, we studied 27 wild rodents (Apodemus agrarius) captured in October and November 2016 in Gwangju, South Korea, and performed nested polymerase chain reaction targeting pyrG and ospA to confirm Borrelia infection. Eight rodents (29.6%) tested positive for Borrelia infection. The heart showed the highest infection rate (7/27; 25.9%), followed by the spleen (4/27; 14.8%), kidney (2/27; 7.4%), and lungs (1/27; 3.7%). The B. afzelii infection rate was 25.9%, with the highest rate observed in the heart (7/27; 25.9%), followed by that in the kidney and spleen (both 2/27; 7.4%). B. garinii and B. burgdorferi sensu stricto were detected only in the spleen (1/27; 3.7%). This is the first report of B. burgdorferi sensu stricto infection in wild rodents in South Korea. The rodent hearts showed a high B. afzelii infection rate, whereas the rodent spleens showed high B. garinii and B. burgdorferi sensu stricto infection rates. Besides B. garinii and B. afzelii, B. burgdorferi sensu stricto may cause Lyme disease in South Korea.