Journal of fish pathology (한국어병학회지)

The Korean Society of Fish Pathology (한국어병학회)
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The pathogenicity of scuticocilate Philasterides dicentrarchi isolated from cultured olive flounder, Paralichthys olivaceus

양식넙치, Paralichthys olivaceus에서 분리된 스쿠티카 섬모충 Philasterides dicentrarchi의 병원성

  • Published : 2006.08.01
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Abstract

In previous study, scuticociliate P. dicentrachi was isolated from farmed flounder during the december 2004 to april 2005. Pathogenicity, mortality and infection symptom were studied using 3 cm and 5 cm groups of juvenile flounder. The ciliates were exponentially increased from bottom layer of the experimental tanks, which propagated within 2000 cells/ml (1.4 × 103 cell ㎖-1 ～ 2.5 × 103 cell ㎖-1) after 6 days of inoculation. The middle layer was maintained within 300 cells/ml. Both 3 cm and 5 cm groups were infected with ciliates, mainly 3 cm group showed high mortality during the experimental period. The death of 3 cm group was started from 5 days and showed 95.6% of mortality after 28 days of first inoculation. The control group showed 4.4% of mortality however, we could not observed any ciliates. The death of 5 cm group was started later than 3 cm group after 18 days of first inoculation. The total mortality was 71% during 28 days. No mortality and infection symptoms were observed in the control. We also studied SSU rRNA gene of ciliates which, re-isolated from infected flounder of experimental groups. When SSU rRNA in this study compared with previous data showed that the identified strain of both previous and present study was same.

2004년 12월부터 2005년 4월까지 양식넙치에서 분리된 스쿠티카 섬모충 P. dicentrarchi를 넙치 치어 3 ㎝ 그룹과 5 ㎝ 그룹에 인위 감염시킨 후 감염에 따른 폐사율 등의 병원성을 조사하였다. 소형수조에 스쿠티카충 P. dicentrarchi를 접종시킨 결과 수조저면에서 활발히 증식하였으며 접종 후 6일째부터 1.4 × 103 cell ㎖-1～2.5 × 103 cell ㎖-1범위로 ㎖당 2,000 cell 내외의 밀도로 증식하였다. 반면에 중층인 경우는 ㎖당 300 cell 이하의 낮은 밀도를 유지하였다.수조저면에 P. dicentrarchi충을 증식시킨 후 넙치치어를 방양한 결과 3 ㎝ 그룹과 5 ㎝ 그룹 모두 배양시킨 충에 감염되었으며, 충 감염에 의한 폐사는 3 ㎝ 그룹인 경우 치명적이었다. 접종 후 5일째부터 폐사가 시작되었으며, 28일 만에 95.6%의 높은 폐사율을 보였다. 대조구에서는 실험기간 동안 4.4% 폐사율을 보였으나 스쿠티카충은 검출되지 않았다. 5 ㎝ 그룹은 접종 후 18일째에 처음으로 폐사되기 시작하여 3 ㎝ 그룹에 비해 폐사 진행이 현저히 늦었다. 이 그룹은 스쿠티카충의 인위 접종 후 28일 동안 71%가 폐사하여 3 ㎝ 그룹에 비해 폐사율이 낮았다. 5 ㎝ 그룹의 대조구에서는 실험기간 동안 폐사가 없었으며 스쿠티카충의 감염도 없었다.모든 실험구의 폐사어에서 인위 감염시킨 충을 재분리하여 SSU rRNA에 대한 유전학적 분석결과, 처음 접종시킨 P. dicentrachi와 각 실험구별 재분리된 섬모충의 SSU rRNA 유전자가 일치하여 동일 섬모충에 의한 감염임이 확인되었다.

Keywords

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