Diagnosis of Viral Epidermal Hyperplasia of Japanese Flounder Larvae by Fluorescent Antibody Technique.

The first occurrence of “viral epidermal hyperplasia" of Japanese flounder larvae was recorded in Hiroshima Prefecture in 1985, and since then the same disease has been prevailing in hatchery-reared flounder in various districts of Japan. In the present study, we applied fluorescent antibody technique (FAT) to the disease as a diagnostic procedure. Electron microscopy and transmission experiments revealed that 4 out of 5 cases examined were due to viral epidermal hyperplasia. FAT test, using a rabbit antiserum against virus particles collected from epithelial cells of affected flounder larvae, exhibited a positive reaction on only the epidermis of the fish in the above 4 epizootics. Thus, the FAT method proved to be useful for rapid diagnosis of the present disease

Diagnosis of viral epidermal hyperplasia of Japanese flounder larvae by fluorescent antibody technique.

The first occurrence of “viral epidermal hyperplasia" of Japanese flounder larvae was recorded in Hiroshima Prefecture in 1985, and since then the same disease has been prevailing in hatchery-reared flounder in various districts of Japan. In the present study, we applied fluorescent antibody technique (FAT) to the disease as a diagnostic procedure. Electron microscopy and transmission experiments revealed that 4 out of 5 cases examined were due to viral epidermal hyperplasia. FAT test, using a rabbit antiserum against virus particles collected from epithelial cells of affected flounder larvae, exhibited a positive reaction on only the epidermis of the fish in the above 4 epizootics. Thus, the FAT method proved to be useful for rapid diagnosis of the present disease

Vaccination Trials in the Japanese Flounder against Edwardsiellosis

ヒラメに対し, Edwardsiella tardaのホルマリン死菌を用いて, 注射免疫, 浸漬免疫, および経口免疫を施し, 注射, 浸漬もしくは経口攻撃を行った。注射免疫および経口免疫区では血清抗体価の上昇とある程度の死亡の遅れが認められたが, いずれの場合も免疫の効果は低かった。浸漬免疫区では抗体価の上昇はなく, 防御能の強化もほとんど認められなかった。E.tardaの菌体外産物および菌体成分にヒラメに対する致死毒性が認められたため, これらの粗毒素を用いて注射免疫を行ったが, ホルマリン死菌と同様防御効果は認められなかった。The Japanese flounder (Paralichthys alivaceus) were vaccinated with formalin-killed cells (FKC) of Edwardsiella tarda by intramuscular injection, immersion and oral administration. Fish were also immunized by injection with diluted extracellular products (ECP) and intracellular components (ICC) of the bacterium, both of which were found lethal to flounder. As a result, mean serum agglutinating antibody titers against FKC rose in all the immunized fish groups except those vaccinated by immersion with FKC. When the immunized and control fish were challenged by injection and immersion with live cells, death was delayed in most of the immunized groups. However, clear protection was not observed in any group immunized either with FKC, ECP or ICC

Infection Experiments with Edwardsiella tarda in the Japanese Flounder

Infection experiments in the Japanese flounder (Paralichthys olivaceus) with Edwardsiella tarda were conducted by intramuscular injection, intraperitoneal injection, immersion, and oral administration methods. Mortalities were produced by all the methods tested, LD50 being determined as 7.1 X 10^1 CFU/fish by intramuscular injection, 1.7 X 10^2 CFU/fish by intraperitoneal injection, 3.6 X 10^6 CFU/ml by immersion, and 1.3 X 10^6 CFU/fish by oral administration. These results show that the Japanese flounder has high susceptibility to E. tarda. Mortalities continuously occurred during the observation period of 15 or 20 days showing a chronic nature of the disease