In vivo antiviral effect of 9-(2-hydroxyethoxymethyl) guanine on experimental infection of chum salmon (Oncorhynchus keta) fry with Oncorhynchus masou virus (OMV).

The therapeutic efficacy of 9-(2-hydroxyethoxymethyl) guanine (Acyclovir, ACV) was evaluated using Oncorhynchus masou virus (OMV) and chum salmon fry. The fish, which were experimentally infected with OMV, were treated with ACV either orally or by the immersion method. Daily immersion of fish into ACV solution (25 microgram/ml, 30 min/day, 15 times) reduced mortality of the infected fish. Oral administration of the drug (25 microgram/fish per day, 60 times) did not affect survival of the chum salmon. On the contrary, the group administered 5-iodo-2'-deoxyuridine (IUdR) by the oral route showed a higher survival than the ACV-administered group. This suggested that an effective level of ACV was not maintained in fish given the drug by the oral route. Daily immersion of infected fish into ACV solution (25 microgram/ml, 30 min/day, 60 times) considerably suppressed the development of tumors induced by OMV.