Abstract
The distribution of iridoviruses in five freshwater ornamental fishes, pearl gourami (Trichogaster leeri), dwarf gourami (Colisa lalia), silver gourami (Trichogaster microlepis), blue gourami (Trichogaster trichopterus sumatranus) and freshwater angelfish (Pterophyllum scalare), imported from Singapore was examined in 2004 and 2005. The presence of iridoviruses in 56 sample groups was determined using PCR technique and showed PCR positive in 11 sample groups. The proportion of fish infected by iridovirus was differed depending upon species; 31.8% (7/22) for pearl gourami, 18.2% (2/11) for dwarf gourami, 16.7% (1/6) for blue gourami, 9.1% (1/11) for silver gourami and 0% (0/6) for angelfish. In quantitative comparison of viral DNAs isolated from infected tissues, the DNA concentration of iridovirus in pearl gourami was higher than that in dwarf gourami. Although pearl gourami infected naturally by iridovirus showed 100% mortality in keeping experiment for 3 weeks, only 57% of those was positive in PCR. In the comparison of nucleotide sequences of the PstⅠ fragment known as the most variable genomic region, both iridoviruses isolated from pearl gourami and dwarf gourami showed identity more than 99% with infectious spleen and kidney necrosis virus (ISKNV) isolated from mandarinfish (Siniperca chuatsi).
2004~2005년까지 수입산 pearl gourami (Trichogaster leeri), dwarf gourami (Colisa lalia), silver gourami (Trichogaster microlepis), blue gourami (Trichogaster trichopterus sumatranus) 그리고 freshwater angelfish (Pterophyllum scalare) 등 5 어종을 대상으로 iridovirus 감염 실태를 PCR 방법을 사용하여 조사하였다. 채집한 56 samples 중 11 samples에서 PCR 양성 반응이 관찰되었고, pearl gourami에서 31.8% (7/22)로 가장 높은 감염 빈도를 나타내었다. 그 다음으로 dwarf gourami, blue gourami, silver gourami 순으로 나타났으며, freshwater angelfish에서는 iridovirus가 검출되지 않았다. 자연 감염된 관상어종의 비장으로부터 iridovirus의 핵산을 분리하여 검출한계 PCR 방법으로 viral DNA의 양을 비교하였으며, dwarf gourami에 비해 pearl gourami에서 더 많은 viral DNA가 검출되는 것을 확인하였다. 자연 감염이 확인된 pearl gourami groups는 실험실 환경에서 100% 폐사하였고, 폐사어 중 57% 이상이 PCR 양성 반응을 나타내었다. PstⅠfragment의 염기서열 비교에서 pearl gourami와 dwarf gourami에서 분리한 iridoviruses는 중국의 mandarinfish (Siniperca chuatsi)에서 분리된 infectious spleen and kidney necrosis virus (ISKNV)와 99% 이상의 매우 높은 상동성을 나타내었다.