Abstract
We previously monitored nervous necrosis virus (NNV) in brain samples of artificially produced walleye Pollock (Gadus chalcogrammus) seedlings, with a low prevalence (1.8%, 1/55) but no clinical symptoms. Given that this virus is considered one of the most serious viral threats for almost all marine aquaculture fish species and characterized by both vertical and horizontal transmission, it would be interesting to monitor NNV in the fertilized eggs as well. We collected fertilized walleye pollock eggs from the farms located in Goseong during January to March, 2017. Approximately 50 mg of eggs were periodically taken from 4 each different batches, and 37 different pooled sample sets in total were made during sampling period. RNA was extracted from the eggs by using Trizol and cDNA was synthesized for RT-PCR for detecting NNV. Primers and PCR conditions are the same as previously described. As a result, NNV was not detected from any of the sample sets by one step PCR (0%, 0/37), suggesting NNV may not be a threat in walleye pollock aquaculture in Korea at present time. However, continuous monitoring for NNV should be conducted because introducing a new species into aquaculture industry involves potentials of disease outbreak and NNV is already known to cause outbreaks in gadoid fishes.
2017년 1월에서 4월까지 강원도 고성에서 사육중인 명태 친어로부터 수정란을 채집하여 신경괴사증바이러스(nervous necrosis virus, NNV)의 검출을 시도하였다. 매 회 50 mg씩 수정란을 채집하여 이를 1 set로 간주하였으며 총 37 set를 제작하였다. RNA를 추출하고 cDNA를 합성하여 NNV를 대상으로 reverse transcriptase PCR을 실시하였다. 그 결과, one-step PCR법으로는 37 set의 시료가 모두 음성이었으며, two-step PCR법으로는 5.4% (2/37)의 시료가 양성을 나타내었다. 그러나, band의 농도가 매우 낮아 시퀀싱은 불가능하였다. 본 연구의 결과 및 이전 연구의 결과로부터 현재 국내에서 양식하고 있는 명태에서 NNV 감염에 의한 폐사는 발생하지 않는 것으로 추정된다. 하지만, 지속적인 모니터링 및 양성 개체 출현 시 바이러스 분리의 시도 등은 필요할 것으로 생각된다.
