ABSTRACT-The survivability of koi herpesvirus (KHV) in environmental water and sediment was evaluated using CCB cells. Samples were collected from Ibaraki prefecture, Kanagawa prefecture and Hakodate, Hokkaido. Significant reduction in the infectious titer of KHV was observed within 3 days in intact environmental water or sediment. However, KHV infectivity remained for more than 7 days in autoclaved or filtered (0.45 mm) water. In the autoclaved water containing sediment, KHV infectivity dropped below detectable limits within 7 days after inoculation. Ten of the 147 bacterial strains from rivers in Kanagawa, and two of the 62 bacterial strains from water from, Hakodate showed anti-KHV properties. The results suggest that in the absence of hosts, KHV can be rapidly inactivated in environmental water.

Since its first outbreak in Japan in 2003, koi-herpesvirus (KHV) remains a challenge to the carp Cyprinus carpio L. breeding industry. In this study, inactivation of KHV in water from carp habitats (carp habitat water) was investigated with the aim of developing a model for rapidly inactivating the pathogen in aquaculture effluent. Experiments with live fish showed that, in carp habitat water, KHV lost its infectivity within 3 days. Indications were that inactivation of KHV was caused by the antagonistic activity of bacteria (anti-KHV bacteria) in the water from carp habitats. Carp habitat water and the intestinal contents of carp were therefore screened for anti-KHV bacteria. Of 581 bacterial isolates, 23 showed anti-KHV activity. An effluent treatment model for the disinfection of KHV in aquaculture effluent water using anti-KHV bacteria was developed and evaluated. The model showed a decrease in cumulative mortality and in the number of KHV genome copies in kidney tissue of fish injected with treated effluent compared with a positive control. It is thought that anti-KHV bacteria isolated from the intestinal contents of carp and from carp habitat water can be used to control KHV outbreaks.

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水産廃棄物であるヒトデの有効利用を目的に，魚類飼育排水処理施設由来細菌のヒトデ成型骨片への付着性を検討した。5 回洗浄を行った後でも，ヒトデ成型骨片の生菌数は 10^8 CFU/g 程度であった。また，ヒトデ成型骨片と市販ろ材への細菌の付着量を比較したところ，どのろ材も洗浄後の生菌数は 10^7 CFU/g 程度であった。以上の結果から，ヒトデ成型骨片は市販ろ材と同様に細菌付着用のろ材として使用できることが明らかとなった。短