A new non-occluded baculo-like virus was detected from black tiger shrimp (Penaeus monodon) with yellow head disease in the southern part of Thailand. Virus particles observed in necrotic tissues of gills and lymphoid organ were bacilliform in shape, ranging from 150-200 nm in length and 40-50 nm in diameter, and were enveloped singly by a trilaminar unit membrane. From the experimental infection trials, it was assumed that this virus was the most virulent among the viruses which have been known in the black tiger shrimp, to date. Pathogenicity and some characters of the virus as well as pathological changes caused by this virus were described.
A cDNA clone encoding the c-myc gene has been isolated from the common carp (Cyprinus carpio). This clone consisted of 1334 base pairs (bp) and contained the whole exonIII and most of exonII of c-myc gene of carp. The derived amino acid sequence showed higher homology to that of rainbow trout (71.5%) and lower to humans (55.0%). The significance of the use of the clone as a probe for the analysis of fish tumors was discussed.
Since 1980, a disease called “Jaundice”, which is characterized by a yellow coloration of the skin and muscle, has been known to cause varying mortalities of 5-20 percent in cultured yellowtail, Seriola quinqueradiata, in Japan. Hematological and bacteriological studies were carried out to clarify the cause of the disease. The diseased fish exhibited low hematocrit values and high plasma bilirubin concentrations. Thin rod-shaped organisms stained with Giemsa were found on the blood smear preparations of all the diseased fish examined. Among 8 culture media examined, only L-15 medium supplemented with 10% fetal calf serum and nutrient broth gave successful result to culture the organisms, the former yielding better growth. On electron microscopy the organism is a single cell, having a cell wall and an inner membrane but no nuclear membrane. Thus, the organism is considered as a bacterium. Morphological and culture characteristics together with its pathogenicity indicate that the bacterium is different from any known species of fish pathogenic bacteria. Inoculation of the isolated bacteria to yellowtail produced high mortalities and symptoms similar to those observed in spontaneous jaundice yellowtail, and the same bacteria were reisolated from all the dead fish in the infection experiment. From these results, it is concluded that the jaundice of yellowtail is an infection caused by an unknown pathogenic bacteria.
A new epizootic characterized by death with a deformity of the body occurred in cultured yellowtail fingerings, Seriola quinqueradiata. A virus was isolated from the diseased fish. The virus replicated and produced cytopathic effects on CHSE-214, EPC, BF-2, FHM, EK-1 and RTG-2 cells. Treatment with IUdR indicated that the virus contained RNA. Electron microscopy revealed that the virions were non-enveloped, hexagonal in shape with diameter of 65-69 nm. Intraperitoneal injection of the virus to yellowtail fingerings induced death with deformity similar to those observed in spontaneously diseased fish at 20°C but not at 26°C. The virus was reisolated from all the dead fish experimentally infected. These results indicate that this virus is the causative agent of the death with deformity of yellowtail fingering.
The ciliate causing scuticociliatosis in Japanese flounder was isolated, and axenic cultures were established. Sterilization of the ciliate was accomplished by serial washing with capillary pipettes. Growth of the ciliate was compared in different dilutions of Millport S solution containing 2% proteose peptone and 1% yeast extract at different temperatures. Optimum growth was obtained at dilution of 1 : 2 (osmolarity : 438 mOsm) at 22.5-27.5°C with a maximum cell density of 1.0×104 cells/ml.
A field survey indicated that Branchiura sowerbyi was the only species of oligochaete in a KED (kidney enlargement disease) -enzootic goldfish farm and that the oligochaete was infected with four species of actinosporeans : Neoactinomyxon sp., Raabeia sp. and two species of Aurantiactinomyxon. When goldfish showing external symptoms of KED were kept together with B. sowerbyi for 2-7 months, the prevalence of infection of B. sowerbyi with Neoactinomyxon sp. significantly increased. It was thus suggested that the myxosporean Hoferellus carassii transformed into the actinosporean Neoactinomyxon sp. in the oligochaete B. sowerbyi. Specific pathogen free goldfish became infected with H. carassii after coexistence with the oligochaete releasing Neoactinomyxon sp. for 4 months.