College of Veterinary Medicine, Chungnam National University, Yousung-gu, Taejeon 305-764, Korea
aCollege of Veterinary Medicine, Chonbuk National University, Jeonju, Jeonbuk 561-756, Korea
Address for correspondence: Joon-Seok Chae, College of Veterinary Medicine, Chonbuk National University, Jeonju, Jeonbuk 561-756, Korea. Fax: +82-63-270-3778.
jschae{at}moak.chonbuk.ac.kr
Ann. N.Y. Acad. Sci. 990: 239-247 (2003).
We provide evidence of
Neorickettsia (
Ehrlichia)
risticii Holland,
the agent of Potomac horse fever, in trematode larval stages
found in aquatic snails and insects collected from a stream
in Korea, using nested polymerase chain reaction (PCR) and sequence
analysis of the 16S rRNA gene fragment amplified from several
cercaria species. It was observed that of 423 (13.1%) of 3,219
snails infected with cercariae, 77 (20.8% of the 371) were infected
with
N. risticii. Five families of trematode cercariae, Schistosomatidae,
Echimostomatidae, Heterophyidae, Microphallidae, and Acanthocopidae
were identified morphologically within
Semisulcospira libertina,
Radix auricularia coreana, and
S. gottschei snails.
Echinostoma cinetorchis,
E. hortense, and
Metagonimus sp. were identified
based on both the cercarial morphology as well as by phylogenetic
analysis of the amplified 18S rRNA gene sequences. Adult aquatic
insects were also collected from the same sites and were sorted
into five species,
Ischnura asiatica in Coenagrionidae and
Calopteryx japonica,
Sympetrum darwinianum,
Symptrum eroticum, and
Symptrum parvulum in Calopterygoidae. One thousand and two hundred eighty
five metacercariae (classified into groups A through F) were
isolated from 310 adult aquatic insects, and the average number
of metacercariae per aquatic insect was 4.1. However, there
was no amplification of
N. risticii from these metacercariae.
