Infection Status of Metacercaria in Adult Dragonflies from South Korea

The dragonfly serves as a second intermediate host of some trematodes. Seven species of dragonflies, Sympetrum drawinianum, Orthetrum albistylum, Lyriothemis pachygastra, Sympetrum eroticum, Crocothemis servilia, Pantala flavescens and Sympetrum pedemontanum were surveyed. The most abundant species among these dragonflies were S. drawininanum, S. eroticum and C. servilia (2,118 and 620 and 334 individuals, respectively). And, the least abundant dragonflies were S. pedemontanum, L.pachygastra and O albistylum (25, 57 and 62 individuals, respectively). Among these intermediate hosts, S. eroticum had the highest infestation rate of metacercaria per individual (11.71%). The infestation rates of two dragonflies, S. drawinanum and S. pedemontanum (8.58% and 4.56%, respectively) also were higher than those of the other four species. In artificial infection studies using animal hosts, we could identify the infections of adult P. muris and P. japonicus from only mouse, in which the infestation rates of P. muris and P. japonicus were 90% and 95% among 20-tested individuals, respectively. Interestingly, adult L. liberum was detected from only frog, R. nigromaculata and the rates of the infestation in frogs were 97.5% among 50-tested frogs. These results suggest that the population size of dragonfly is an important factor to carry high burden of metarcercaria. Moreover, we discussed their epidemiological implications for human and animal infections.