In the present study, occlusion bodies (OBs) of Penaeus monodon-type baculovirus (MBV) were collected from infected juvenile P. monodon and then the OBs were purified by centrifugation for 30 min at a speed of 100, 000×g using 35-65% (w/w) sucrose gradient. Analysis of polypeptides of MBV occlusion bodies showed 12 polypeptides in SDS-PAGE gel. It was also concluded that the major band with molecular mass of 62k dalton may be derived from protein of polyhedrin.
A comparison was made of the in vitro activities of five quinolone antibacterials (nalidixic acid, piromidic acid, oxolinic acid, flumiquine and miloxacin) currently used in aquaculture in Japan and five newer quinolones (ofloxacin, norfloxacin, enoxacin, ciprofloxacin and tosufloxacin), against selected fish bacterial pathogens. Of the earlier quinolones, flumiquine and oxolinic acid showed the highest bacteriostatic and bactericidal activities against Gram-negatives. The newer quinolones, however, showed considerably higher activities, with ciprofloxacin and tosufloxacin most active. The newer quinolones were also active against strains resistant to the earlier quinolones. Grampositive bacteria were resistant to all the earlier quinolones, but some strains were sensitive to the newer quinolones, particularly to ofloxacin, ciprofloxacin and tosufloxacin. The activities of the newer quinolones were found to be less affected by serum, pH or the addition of magnesium, than the earlier quinolones. The newer quinolones were considered to have potential for the treatment of Gram-negative, and possibly Gram-positive, bacterial fish pathogens.
Infectivity and organ distribution studies for the rhabdovirus (rhabdovirus of penaeid shrimp-RPS) isolated from Penaeus spp. were conducted with subadult Penaeus stylirostris. Test shrimp were inoculated intramuscularly with different isolates of RPS from penaeid shrimp collected from different shrimp farms in Hawaii and Ecuador. Although the experimentally infected shrimp showed no clinical or gross manifestations of disease, the RPS was found to be infectious for the animals. Virus replication was demonstrated only in the lymphoid (Oka) organs of infected shrimp by virus assay and immunofluorescence. Also, the Oka organs of infected animals showed gross cellular changes and were significantly larger in size than the corresponding organs from uninfected shrimp. A possible role of the RPS in the causation of disease in penaeid shrimp is postulated.
Phagocytic activity of the pronephric and peripheral blood neutrophils was studied in the eel, Anguilla japonica, injected with physiological saline or bacterial cells. In phagocytosis, i.e. phagocytic rate and phagocytic index, and chemiluminescent response, the neutrophils from the bacteriainjected eel showed higher activity than those from the saline-injected eel, and the peripheral blood neutrophils were more active than the pronephric ones. It is concluded that in response to the bacterial stimulus, the hematopoietic tissues of the kidney supply neutrophils with higher phagocytic activity to the peripheral blood.
The susceptibility of different sizes of coho salmon (Oncorhynchus kisutch) and of several other salmonid species to erythrocytic inclusion body syndrome (EIBS) was investigated using artificially induced infections. The sizes (body weight) of the coho salmon examined were 1.2, 4.5, 13.4, 23.2, 31.2 and 220.3 g. Susceptibility of rainbow trout (Oncorhynchus mykiss), masu salmon (Oncorhynchus masou) and chum salmon (Oncorhynchus keta) of 2.4 to 5.7 g were compared to that of coho salmon. Severity of infection was evaluated by erythrocytic inclusions and Ht values. All the sizes of coho salmon had similar susceptibility to EIBS. Chum salmon and masu salmon were as sensitive to EIBS as coho salmon but rainbow trout were less sensitive than coho salmon.
A humoral immune response of the Japanese eel (Anguilla japonica) against major antigens from the microsporean Pleistophora anguillarum was detected. Sonicated spores recovered from the skeletal muscle of infected “beko” eels were run on sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. The separated proteins were then electroblotted onto nitrocellulose and incubated in dilutions (1 : 100, 1 : 200 and 1 : 300) of sera from infected or non-infected eels. For secondary and tertiary incubations, a rabbit anti eel Ig serum and peroxidase conjugated swine anti rabbit Ig antibodies were used, respectively. The reaction pattern varied among eels, but it was demonstrated that the sera of infected eels responded strongly to at least one of the proteins with approximate molecular weights of > 94, 89, 62, 52, 45, and 32 kDa. Some sera of non-infected eels from the same culture ponds showed a lower reactivity to the > 94, 62, 52 and 32 kDa proteins (serum dilution 1 : 100) but no sera responded to any proteins when they were diluted 1 : 200 and 1 : 300.
We studied the ability of Amyloodinium ocellatum to infect gill cell cultures in the presence of serum or mucus from naive blue tilapia Oreochromis aureus. Serum concentrations as low as 1.25 % markedly inhibited parasite infectivity. Serum concentrations greater than 10 % were completely inhibitory. Mucus had considerably less inhibitory activity than serum. Heating serum to 47°C for 20 min or 56°C for 30 min, as well as treating serum with zymosan or carrageenan, suggested that a complement-like factor was responsible for at least some of the activity, but that other factors may also influence parasite infectivity.