Furunculosis vaccines were prepared from virulent strains of Aeromonas salmonicida: 2 were formalin killed bacterins, and 3 were “cell surface extracts” prepared by stirring the bacteria in lithium acetate-EDTA buffer at different pH in presence of glass beads. Rainbow trout were vaccinated by intra-peritoneal injection and challenged with virulent strains injected intra-muscularly or added to water. Although the challenges were conducted at the wanted levels and provided good reliability, no protection could be demonstrated in any of the tested groups. Techniques and methods of work cannot explain these failures and it is concluded that rainbow trout were not protected. Discrepances of these results with other recent reports are outlined, and some comments are done about the meaning and bearing of furunculosis vaccination studies.
In vitro efficacy of five antibiotics were tested against Streptococcus sp., the causative agent of streptococcal infection in yellowtail. Erythromycin and spiramycin are currentry used to control the disease and had 0.0125-0.39μg/ml minimum inhibitory concentration (MIC) and 0.2-1.56μg/ml MIC respectively. Josamycin, tylosin and lincomycin currentry not used, had respectively 0.1-0.39μg/ml, 0.1-1.56 μg/, ml 0.0125-0.1μg/ml MIC. The time to death kinetics using the five antibiotics were studied. Drug resistance to the antibiotics developed after 10 serial passages in the presence of the antibiotic.
The 24, 48 and 96 h TLm (median tolerance limit) values of zinc to Japanese eel were computed at 29, 14 and 11 mg Zn++/l, respectively. Fish exposed to sublethal concentrations of zinc, were challenged with Edwardsiella tarda to determine the effect of this stressor on susceptibility to the bacterial pathogen. No difference was found in susceptibility between zinc-exposed and non-exposed fish.
Four viruses isolated from fish in Korea were examined for their serological and biochemical properties. Three of the viruses isolated were from chum salmon (Oncorhynchus keta) and the fourth was from the goldfish (Carassius auratus). All were found to be closely related to infectious pancreatic necrosis virus, reference strain VR-299. Immunoprecipitation of virion polypeptides labeled with 35S-methionine was found to be a rapid and specific method to characterize the virus strains particularly when supplemented with serological properties and genome segment analysis.
Changes in bilirubin contents and composition in the bile of starved and CCl4 injected carp Cyprinus carpio were examined by diazo methods. The doses of CCl4 injection were 10, 40, and 100μl/100g body weight. In the bile of control carp, total, conjugated, and unconjugated bilirubin contens were 0.03-0.13, 0.02-0.08, and 0.01-0.02 mg /ml, respectively. During the starvation, total and conjugated bilirubin contents gradually increased but unconjugated bilirubin contents did not change. After 30 days, total and conjugated bilirubin contents were 22-26 times higher than those of control. In the bile of CCl4 injected carp, total and conjugated bilirubin contents increased rapidly. Both contents were 8-18 times higher than those of control one day after injection. Unconjugated bilirubin contents in carps injected with 40μl and 100μl CCl4 were increased 5 days and 2 days after injection, respectively.
A microscopical examination was made on cultured tiger puffer, Takifugu rubripes suffering from “Kuchijiro-sho” (mouth ulceration) collected from the Amami-oshima island in Kagoshima Prefecture from 1982 to 1983. The disease occurred among young fish and was characterized by erosion and ulceration of the snout and by biting each other. The histopathological change found in all diseased fish was the production of inclusion-like bodies in the nucleus of nerve cells, resulting in necrosis of the affected cells in the medulla oblongata. The feature of nerve cells with inclusion-like bodies had a resemblance to that of “owl's-eye” (NAKAO et al., 1980; ONO et al., 1983). found in virus infected cells of human. The affected snout showed erosion and ulceration in the skin with/without bacterial invasions.
In 1982 to 1984, 3 cases of Pseudomonas anguilliseptica infection occurred in pond-cultured ayu, Plecoglossus altivelis, in Shizuoka Prefecture. The outbreaks of the disease have been reported exclusively in eels, thus this is the first record of the infection in ayu fish. Biochemically, the isolates from diseased ayu were identical to P. anguilliseptica isolates from eels (Anguilla japonica and A. anguilla). However, the ayu-isolates were proved different from eel-isolates in the pathogenicity to ayu and Japanese eel, resistance to bactericidal action of normal fish sera, and a surface antigen.
Chronic mortalities have been a recurrent problem in common goldfish Carassius auratus throughout the United States and a coccidian, morphologically identical to Goussia carpelli, is suspected to be the primary etiological agent. This parasite may cause severe mortalities due to enteritis in cultured carp Cyprinus carpio in Europe and the pathology and epizootiology was similar in goldfish. In our study, goldfish became infected shortly after hatching and sporulated oocysts were found in 15-day-old fish. Fish are usually harvested from ponds after six weeks and are shipped to wholesalers. At this time they stopped feeding, became lethargic, emaciated, and cumulative mortalities of 50-75% occurred over a two to three week period. Necropsies revealed a chronic enteritis with numerous sporulated oocysts surrounded by yellow bodies in the lamina propria of the intestine. Most of the oocysts were shed or degenerated as the disease progressed, but fish continued to die. Histological analyses of these fish revealed numerous yellow bodies, inflammatory and necrotic cells in the lamina propria of the gut and the intestines often had lost their villar structure. The yellow bodies, identified as lipofuscin or ceroid by electron microscopy and histochemical analysis, were also found in the spleen and kidney of severely affected fish. Experimental infection in the laboratory was accomplished using tubificid worms and grass shrimp(Palaemonetes kadiakensis)fed oocysts, but direct transmission of the parasite using fresh or cold aged occysts was unsuccessful.
Studies were made on histopathology of cultured tiger puffer with “Kuchijiro-sho” collected from some fish farms in Nagasaki Prefecture from July to December, 1984. The fish were characterized by erosion and ulceration of the mouth, dark body coloration and biting aggressively each other. Internally, linear superficial hemorrhage in the liver was commonly observed. The main histopathological change was found in the large nervous cell at the nucleus of the 8-10th cranial nerve and supramedullary neuron. The change was characterized by formation of some masses in the nucleus and the deformed shape of the nucleus of the large nervous cell and supramedullary neuron. The mass in the nucleus had slight change of coloration for some kinds of stain. Electron-microscopical examination was made on the nucleus of cranial nerves of the medulla oblongata; as a result, virus-like particles were observed either as a mass-type in the nucleus or as scattering-type on the deformed nuclear membrane. Judging from the histopathological and electron-microscopical findings, a possibility was suggested that the disease called “Kuchijiro-sho” was caused by virus infection.