Tick surveillance in two southeastern provinces, including three metropolitan areas, of the Republic of Korea during 2014

Abstract

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).