ABSTRACT
The Korea Disease Control and Prevention Agency has established regional centers at 16 locations to monitor vectors and pathogens. We investigated the geographical and temporal distribution of chigger mite populations to understand tsutsugamushi disease epidemiology in 2020. To monitor weekly chigger mite populations, 3637 chigger mites were collected from sticky chigger mite traps in autumn. Chigger mites appeared from the first week of October to the third week of December, peaking in the fourth week of October. The predominant species were Leptotrombidium scutellare, Leptotrombidium palpale, Neotrombicula kwangneungensis, Neotrombicula tamiyai, and Leptotrombidium pallidum. To monitor Orientia tsutsugamushi infection in chigger mites, 50,153 chigger mites were collected from 499 trapped wild rodents in spring and autumn, with a chigger index of 100.5. Approximately 50% of chigger mites were pooled into 998 pools, and the minimum infection rate (MIR) of O. tsutsugamushi was 0.1%. Jeongeup had the highest MIR for O. tsutsugamushi (0.7%). The Kato-related genotype was the most common (52.2%), followed by the Karp-related (17.4%), Boryong (13.0%), JG-related (8.7%), Shimokoshi (4.3%), and Kawasaki (4.3%) genotypes. Ecological and geographical studies focusing on the basic ecology and pathology of mites will improve our understanding of tsutsugamushi disease risks in the Republic of Korea.
ABSTRACT
Since 2010, the Korea Disease Control and Prevention Agency has established centers at 16 locations to monitor disease vectors and pathogens. Here, we examined tick populations to understand the geographical and temporal distribution of severe fever with thrombocytopenia syndrome virus (SFTSV) vectors in 2020. From April to November, 63,376 ticks were collected from traps to monitor tick populations, with a trap index of 41.3. Tick incidence varied from April to October, with population peaks observed for nymphs in May, adults in July, and larvae in September. The predominant tick species were Haemaphysalis longicornis, Haemaphysalis spp., H. flava, Ixodes spp., Amblyomma testudinarium, and Ixodes nipponensis. Approximately 50% of the collected ticks were pooled into 2973 groups to detect the rate of SFTSV infection in ticks. The minimum infection rate (MIR) of SFTSV was 0.2%, and Andong had the highest MIR for SFTSV (4.0%). The B3 genotype was the most prevalent (52.2%) followed by B2 (28.6%), B5 (15.9%), B4 (1.6%), and B6 (1.6%). We identified widely distributed tick species and a high degree of diversity in SFTSV strains in ticks from different geographical regions. The results may provide a basis for future epidemiological studies and risk assessments for tick-borne diseases.
ABSTRACT
Babesiosis is a tick-transmitted intraerythrocytic zoonosis. In Korea, the first mortalities were reported in 2005 due to Babesia sp. detection in sheep; herein we report epidemiological and genetic characteristics of a second case of babesiosis. Microscopic analysis of patient blood revealed polymorphic merozoites. To detect Babesia spp., PCR was performed using Babesia specific primers for ß-tubulin, 18S rDNA, COB, and COX3 gene fragments. 18S rDNA analysis for Babesia sp., showed 98% homology with ovine Babesia sp. and with Babesia infections in Korea in 2005. Moreover, phylogenetic analysis of 18S rDNA, COB, and COX3 revealed close associations with B. motasi. For identifying the infectious agent, Haemaphysalis longicornis (296) and Haemaphysalis flava (301) were collected around the previous residence of the babesiosis patient. Babesia genes were identified in three H. longicornis: one sample was identified as B. microti and two samples were 98% homologous to B. motasi. Our study is the first direct confirmation of the infectious agent for human babesiosis. This case most likely resulted from tick bites from ticks near the patient house of the babesiosis patient. H. longicornis has been implicated as a vector of B. microti and other Babesia sp. infections.
