Interaction between fish pathogenic viruses and microorganisms in fish rearing water: Survival and inactivation of infectious pancreatic necrosis virus, infectious hematopoietic necrosis virus and Oncorhynchus masou virus in [salmonid] rearing water

The survival of three salmonid viruses; infectious hematopoietic necrosis virus (IHNV), infectious pancreatic necrosis virus (IPNV) and Oncorhynchus masou virus (OMV), in fish rearing water, dechlorinated city water, double-distilled water, and Hanks' BSS were observed at 0, 5, 10 and 15°C. In addition, interaction between viruses and microorganisms present in the rearing water was observed. The results obtained are summarized as follows: 1. IPNV was stable in all kinds of waters employed at every temperature tested for 14 days, but it was observed that, for IHNV, as the temperature increased, the loss of infectivity also increased. 2. OMV was labile even in Hanks' BSS and inactivated rapidly as the temperature was raised. Infectivity declined to less than minimum observable amount at 14 days postincubation both at 10 and 15°C. It was not survived at 5 to 7 days later in the fish rearing water. 3. When IHNV or OMV was suspended in filtered rearing water, titer reduction of the viruses was suppressed in comparison with the untreated water. This phenomenon was more conspicuous in the autoclaved water. 4. The infectivity of IHNV declined to less than minimum observable amounts at 3 days after incubation at both 5 and 15°C, when it was suspended in filtrated culture to which rearing water was added with 10% MEM 10 and incubated at 15°C for 2 days. In microflora of the culture, Achromobacter and Pseudomonas were dominant and the ratio was 7:3. 5. Representative strains of Pseudomonas has been proven to have the ability to produce anti-IHNV substance.