ABSTRACT
Haemaphysalis longicornis is one of the most medically important carriers of various pathogens. Although H. longicornis is an important vector, only basic ecological and biological information has been obtained, primarily focusing on its abundance and distribution. This study determined the most active time and meteorological conditions for the diel activity of H. longicornis. The diel activity pattern of H. longicornis was the highest between 10:00 and 14:00, and the lowest between 22:00 and 02:00. The major activity temperature of H. longicornis was between 25 °C and 40 °C, with the highest activity at 35 °C. The relative humidity was between 30% and 70% during the active period. Temperature had the highest correlation with diel activity (R = 0.679), followed by humidity (R = -0.649) and light intensity (R = 0.572). Our results provide basic information for the development of tick-borne disease vector control programs and tick surveillance.
ABSTRACT
Monitoring mosquito populations is essential for controlling mosquito-borne diseases, and the selection of mosquito traps should be tailored to specific surveillance objectives. Here, we tested four mosquito traps for their efficiency and applicability: the Nozawa-style black light trap (BLT), BG-sentinel trap II (BGT), UV-LED Blackhole Plus Mosquito Buster trap (LED), and digital mosquito monitoring system (DMS). The traps were rotated weekly for a 24 h cycle at the same location for 13 weeks. Overall, 1649 female mosquitoes belonging to seven genera and sixteen species were collected by the traps. The traps exhibited differences in both the number of collected individuals and species composition. The BLT showed superior collection efficiency in terms of the number of collected individuals and species evenness, whereas the BGT showed the highest species diversity among all the traps. Thus, the BLT and BGT are the best choices for effective mosquito surveillance based on trap performance. Additionally, despite the relatively low efficiency of the LED and DMS observed in this study, the LED is known to be efficient when used for indoor conditions such as cowsheds, while the DMS has an advanced function that can automatically count the number of mosquitoes. Thus, our findings provide significant guidelines for planning new mosquito surveillance projects in the ROK.
ABSTRACT
The Korea Disease Control and Prevention Agency has established centers at 16 locations to screen vector populations and pathogens. The aims of this study were to determine the relative spatiotemporal distributions of mosquitoes that are flavivirus vectors, and to correlate them with instances of flaviviral disease in the Republic of Korea (ROK). We collected 67,203 mosquitoes in traps at 36 collection sites in 30 urban regions and migratory bird habitats in 2020. The trap index was 36.6, and the predominant mosquito species were the Culex pipiens complex, Armigeres subalbatus, Aedes albopictus, Aedes vexans, and Culex tritaeniorhynchus. The mosquitoes were pooled into 4953 pools to monitor flavivirus infection. We determined that the minimum infection rate of flavivirus was 0.01%. Japanese encephalitis virus (JEV) was detected in only seven pools of Culex orientalis from Sangju, and we isolated JVE from two pools. All detected JEV was found to be genotype V by phylogenetic analysis. To the best of our knowledge, this is the first study to isolate genotype V JVE from Culex orientalis in the ROK. Subsequent geographical and ecological studies on mosquitoes will help improve our understanding of the relative risk of flavivirus infection. Future studies should analyze mosquito species distribution and improve flavivirus monitoring and long-term surveillance.
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
Aedes albopictus (Skuse, 1894) is a mosquito vector raising global health concerns owing to its transmission of dengue, Zika, and chikungunya viruses. This vector accounts for a large proportion of the Korean mosquito community; however, autochthonous clinical cases resulting from this species remain unreported in South Korea. This study aimed to examine the geographical genetic variations and sources of Ae. albopictus populations in South Korea exclusively on the basis of COI gene analysis from 292 samples collected from 37 localities in 2016-2018 and 290 reference sequences from GenBank. Thirty-eight haplotypes were identified among the 292 Ae. albopictus samples, with H1 (n = 190, 65.1%), H29 (n = 24, 8.22%), and H32 (n = 24, 8.22%) being the most common and widely distributed haplotypes in the mainland, southern coastal region, and Jeju Island, respectively. In general, high haplotype (≥0.5; 44.7%) and low nucleotide (≤0.00148 max.) diversity were observed in these populations. Based on eight regional groups, results of neutral tests and a mismatch analysis supported demographic expansions after bottlenecks. Furthermore, analysis of molecular variance, FST, and K2P distance showed that Gyeongsangnam-do, Jeju Island, and mainland groups were genetically differentiated. Haplotype network and phylogenetic analyses revealed that the sources of the main haplotypes are related to strains from other countries. The current findings need to be validated with additional sampling from heterogeneous habitats and different genetic markers. However, our results suggest that haplotype changes should be closely monitored for efficient vector surveillance and control.