Ticks play an important role in transmission of arboviruses responsible for emerging infectious diseases, and have a significant impact on human, veterinary, and wildlife health. In the Republic of Korea (ROK), little is known about information regarding the presence of tick-borne viruses and their vectors. A total of 21,158 ticks belonging to 3 genera and 6 species collected at 6 provinces and 4 metropolitan areas in the ROK from March to October 2014 were assayed for selected tick-borne pathogens. Haemaphysalis longicornis (n=17,570) was the most numerously collected, followed by Haemaphysalis flava (n=3317), Ixodes nipponensis (n=249), Amblyomma testudinarium (n=11), Haemaphysalis phasiana (n=8), and Ixodes turdus (n=3). Ticks were pooled (adults 1-5, nymphs 1-30, and larvae 1-50) and tested by one-step reverse transcription polymerase chain reaction (RT-PCR) or nested RT-PCR for the detection of severe fever with thrombocytopenia virus (SFTSV), tick-borne encephalitis virus (TBEV), Powassan virus (POWV), Omsk hemorrhagic fever virus (OHFV), and Langat virus (LGTV). The overall maximum likelihood estimation (MLE) [estimated numbers of viral RNA positive ticks/1000 ticks] for SFTSV and TBEV was 0.95 and 0.43, respectively, while, all pools were negative for POWV, OHFV, and LGTV. The purpose of this study was to determine the prevalence of SFTSV, TBEV, POWV, OHFV, and LGTV in ixodid ticks collected from vegetation in the ROK to aid our understanding of the epidemiology of tick-borne viral diseases. Results from this study emphasize the need for continuous tick-based arbovirus surveillance to monitor the emergence of tick-borne diseases in the ROK.

Tick-borne disease surveillance was conducted monthly at different sites in four southwestern provinces of the Republic of Korea (ROK) from April-October 2013. Three general habitats were surveyed: grasses (grasses and herbaceous and crawling vegetation), forests (pine, larch, deciduous, and mixed), and forests+grasses. A total of 27,029 ticks (1,534 adults; 11,755 nymphs; 13,740 larvae) belonging to three genera and five species were collected. Haemaphysalis longicornis (64.76%; 17,504) was the most commonly collected tick, followed by Haemaphysalis flava (29.22%; 7,899), Ixodes nipponensis (5.83%; 1,575), Amblyomma testudinarium (0.17%; 46), and Haemaphysalis phasiana (0.02%; 5). Overall, adult ticks accounted for only 5.68% of all ticks collected, while nymphs and larvae accounted for 43.49% and 50.83%, respectively. Haemaphysalis longicornis nymphs were commonly collected from April-June, followed by increased numbers of adults from June-August, and large numbers of larvae from August-September, while low numbers of all stages were collected during October. Haemaphysalis flava adults and nymphs were commonly collected from April-June and September-October, while large numbers of larvae were collected from July-August. Although fewer I. nipponensis were collected, seasonal developmental stage patterns followed those of H. flava. Similar proportions of males (47.96%) and females (52.04%) of H. flava were collected. However, the proportion of H. longicornis females (85.83%) collected was significantly higher than for males (14.17%), while the proportion of I. nipponensis males (57.62%) was significantly higher than for females (42.38%). Overall, the mean number of ticks collected/hour of collection was highest for forests+grasses (108.54), followed by grasses (97.28) and forests (66.64).

Aedes aegypti is a prominent disease vector that is difficult to control through traditional integrated vector management due to its cryptic peridomestic immature-stage habitat and adult resting behavior, increasing resistance to pesticide formulations approved by the US Environmental Protection Agency, escalating deregistration of approved pesticides, and slow development of new effective chemical control measures. One novel method to control Ae. aegypti is the sterile insect technique (SIT) that leverages the mass release of irradiated (sterilized) males to overwhelm mate choice of natural populations of females. However, one potential liability of SIT is sex sorting errors prior to irradiation, resulting in accidental release of females. Our goal in this study was to test the extent to which irradiation affects female life-history parameters to assess the potential impacts of releasing irradiated females accidentally sorted with males. In this study, we determined that a radiation dose ≥30 Gy—a dose sufficient to sterilize males while preserving their mating competitiveness—may substantially impact longevity, bloodfeeding, oviposition, and egg hatch rate of female Ae. aegypti after being irradiated as pupae. These findings could reduce public concern for accidental release of females alongside irradiated males in an operational Ae. aegypti SIT control program.

Tick-borne disease surveillance was conducted from March–October 2014 in two southeastern provinces, including three metropolitan areas, in the Republic of Korea (ROK). Three general habitats were surveyed: Grasses (grasses and herbaceous and crawling vegetation), Forests (pine, larch, deciduous, and mixed), and Forests+Grasses. A total of 40,048 ticks (1,480 adults; 24,201 nymphs; 14,367 larvae) belonging to three genera and six species were collected. Haemaphysalis longicornis (84.25%; 33,741) was the most commonly collected tick, followed by Haemaphysalis flava (14.52%; 5,816), Ixodes nipponensis (1.09%; 436), Amblyomma testudinarium (0.07%; 27), Haemaphysalis phasiana (0.06%; 23), and Ixodes turdus (0.01%; 5). Overall, adult ticks accounted for only 3.70% of all ticks collected, while nymphs and larvae accounted for 60.43% and 35.87%, respectively. The proportion of H. longicornis nymphs was highest beginning in March (99.51%), slowly declined through July (82.01%) and then rapidly declined to a low in October (6.45%). Large increases in the proportion of H. longicornis larvae were observed in August (42.05%), September (84.19%) and October (93.55%) following increased numbers of adults collected in June (4.20%), July (17.99%) and August (9.79%). Haemaphysalis flava adults and nymphs were commonly collected from April–May and October, while larvae were first collected from July, with peak numbers collected in August and low numbers collected during September–October. The proportion of I. nipponensis adults was highest in March (75.34%), declined to a low in July (0%), and then increased in September (60.00%) and October (90.32%). Larvae were collected only in August–September and accounted for 64.29% and 20.00% of all I. nipponensis collected during those months. Similar proportions of males and females of H. flava (51.47% and 48.53%, respectively) were collected from all habitats, while significantly more I. nipponensis males (62.20%) were collected than females (37.80%). Conversely, the proportion of H. longicornis females (80.00%) collected was significantly higher than for males (20.00%). Overall, the mean number of ticks collected/hr of collection for all habitats was 156.06/hr of collection. Similar numbers were collected/hr for Forests (172.61) and Grasses (168.64), while lower numbers were collected/hr for Forests+Grasses (128.12).