The infectivity of five fish rotaviruses was assayed on 4 fish and two mammalian cell lines at different temperatures. These viruses were isolated recently from turbot (TRV), smelt (SRV), striped bass (SBR) and Atlantic salmon (ASR and HBR). The two mammalian lines, MA 104 and MDBK, were not susceptible to any of the viruses assayed, although viruses were adsorbed by the cells at certain temperatures. Of the four fish cell lines employed (CHSE-214, FHM, EPC and BB), only FHM cell failed to support the the growth of all the viruses. The EPC cells were susceptible, but the titers were low (≤105.5 TCID50/ml). Although the BB cells proved to be very useful for the replication of SRV, the Atlantic salmon rotavirus failed to grow in this cell line. The CHSE-214 cell is the optimal cell line for all these rotaviruses because they produced relatively high titers (between 106.25 and 109.25 TCID50/ml) when the cells were incubated at 15°C.
Properties of hemolysin produced by β-hemolytic Streptococcus sp., isolated from yellowtail (Seriola quinqueradiata) were investigated using the culture supernatant. The hemolytic activity of the toxin against sheep red blood cells reached a maximum after incubation at 25°C for 90 min or at 37 or 50°C for 30 min. The toxin showed higher activity at pH 5.5-6.0 and was intensively inactivated by papain and subtilisin (Bacillus subtilis protease) but was only slightly inhibited by pepsin and β-amylase. Sheep red blood cells were more sensitive to the toxin than rabbit, white-spotted char (Salvelinus leucomaenis) and rainbow trout (Oncorhynchus mykiss) red blood cells.
A comparison of the DNA homologies between five salmonid herpesviruses showed two distinct groupings. Herpesvirus salmonis (HPV) and the steelhead herpesvirus (SHV) appear to be different strains of the same virus. Oncorhynchus masou virus (OMV) andyamame tumor virus (YTV) also appear to be different strains of the same virus, althoughnot as closely related to one another as SHV and HPV. The nerka virus (NeVTA) issimilar yet distinct from OMV and YTV. It appears that the salmonid herpesviruses canthus be classified as follows;Herpesvirus salmonis Type 1 (HPV and SHV, from NorthAmerica) and Herpesvirus salmonis Type 2 (OMV, YTV and NeVTA, from Japan).
Virucidal activities of ethanol, methanol, propanol, phenol, cresol, iodophor and chlorine to infectious hematopoietic necrosis virus (IHNV) were examined. IHNV was inactivated by all the tested germicides : alcoholic germicides, cresol and indophor showed high virucidal activities, while phenol showed rather low virucidal activity. Virucidal activities of phenol and cholrine were decreased by the presence of organic substances. On the other hand, virucidal activities of alcholic germincides and cresol were not effected by organic substances indicating. Advantage of the usage of these disinfectants for inactivation of IHNV.
Virucidal effects of invert soaps on IPNV and IHNV were tested. Three kinds of invert soap formulae were used : two formulae contained benzalkonium chloride and the other contained benzethonium chloride in the ingredient. All formulae inactivated IHNV by the exposure to 0.08% solutions for 15 seconds, but did not inactivate IPNV. Addition of 10% fetal calf serum to IHNV suspension reduced the virucidal activity of invert soaps : a fetal calf serum decreased the virucidal activities of benzalkonium chloride and benzethonium chloride to 1/8-1/4 and 1/16, respectively.
Immunoglobulin (Ig) was purified from the serum of eel (Anguilla japonica) and an indirect enzyme-linked immunosorbent assay (ELISA) was developed for the detection of eel antibody. Sera were collected from eel which had been injected with formalin-killed Edwardsiella tarda bacterin. A pool of the sera was precipitated with a 40% saturated ammonium sulfate solution, and then immunoglobulin was purified from the precipitates by gel-filtration and ion-exchange chromatography. The purified Ig emulsified in Freund's complete adjuvant was administered to a rabbit to prepare anti-eel Ig serum. Eel were immersed in the E. tarda bacterin at a density of 1 mg wet weight/ml for 1 h. Change in antibody titers in the vaccinated fish was determined by indirect ELISA. The titers of vaccinated fish were significantly higher than those of unvaccinated control fish.