• Korean Journal of Microbiology
• /
• v.31 no.2
• /
• pp.113-122
• /
• 1993

Aeromonas veronii was isolated from the haemorrhagic ulcer of the snakehead that had been infected in natural condition, This bacterium was injected hypodermically into the healthy snakeheads and the effect was compared to the naturally infected fish. Both groups showed severe necrosis, falling off of epidermal tissue and hypodermal muscle. In both groups, severe histophathological changes were observed in gill, digestive tract and kidney just before death. Artificially injected fish showed necrosis of tissue in skin, gill and digestive tract from 2 days after injection. Then it showed necrosis or cell atrophy of tissue in kidney from 5 days after injection, and in liver and spleen just before death. Snakehead infected with haemorrhagic ulcer died within 9 days after infection, showing the symptom of skin damage and metabolic inhibition in respiration" digestion, excretion, etc. It was concluded that Aeromonas veronii (CA26) that was isolated from the naturally infected fish is the main bacterium causing haemorragic ulcer in the snakehead.

• Korean Journal of Microbiology
• /
• v.30 no.3
• /
• pp.164-170
• /
• 1992

Haemorrhagic ulcer in cultured snakehead(Chann0 argus) is widespread in Korea during the summer season. Round haemorrhagic ulcers as the main symptom of this epizootic disease can be found on the skin of the head. body, as well as fins of this fish. This study was conducted to investigate the pathology of this disease. First. Aeromonas veronii. the dominant species. was isolated from diseased snakeheads. Then this bacterium was injected into healthy snakeheads hypodermically. Such injection was found to induce haemorrhagic ulcers very similar to those observed in naturally infected fish. One or two days afier the injection, a red spot developed around the injection site. and grew bigger to from a red area. This enlarged area then developed into haemorrhagic ulcer, accompanied by substantial skin loss. Within five days. muscle necrosis proceeded to the extent that a perforation was made between the injection site and the opposite side. The fifty per cent lethal dosage was found to be $1\times10^{5}$CFU/0.25 ml by intraperitoneal injection. The results of this experiment lead us to conclude that Arromonas veronii is a major bacterium which causes haemorragic ulcer in cultured snakcheads.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.23 no.5
• /
• pp.353-360
• /
• 1990

The bacterium Edwardsiella tarda was injected into healthy snakeheads (Channa argus) in order to prove the causative agent of ascite. The bacterium dominantly isolated from 2 cultured ascite snakeheads was injected into fish by the dose of $5\times10^6$ CFU/ 0.25ml, but the same dose of $0.65\%$ physiological saline was injected into the each control. The injected fish was divided into 4 groups such as intraperitoneal, intramuscle, control intra-peritoneal and control intramuscle according to their injection points. Each was composed of 10 healthy snakeheads respectively. Ascites and haemorrhagic ulcers became distinct 5 days after injection, but controls did not show any abnormal symptoms during the experimental period. Edwardsiella tarda was reisalated out of the injected fish's ascite, liver, kidney, spleen and haemorrhagic ulcer on the skin. Regardless of the injecting methods, liver was necrotized more severely than any other internal organ, but both the glomeruli of kidney and spleen were considerably damaged. Necrosis of muscle and a number of leucocytes were observed at the ulcerous region of the intramuscular injected fish. It is concluded that judging from the above results the Edwardsiella tarda is a causative agent to cause ascite in snakehead.

• Korean Journal of Veterinary Service
• /
• v.18 no.1
• /
• pp.22-32
• /
• 1995

A partial characteristics and pathogenicity of Aeromonas salmonicida strain isolated from diseased cultured eel were studied. On the biochemicial characteristics of the isolate strain was classified into atypical Aeromonas salmonicida : the characteristics of the isolate strain differed from those of the subspecies of Achromogenes, masoucida and salmonicida. It strain was named atypical Aeromonas salmonicida EL-1 and it grew at optimal pH 7.5 and l% Nacl. In the pathogenicity test, at one to two days post infection, the motality of artificially infected eels with $1{\times}10^8$ and $1.0{\times}10^7$ cfu/fish group was 100%, and at three days pos-infection, in the $1.0{\times}10^6$ /cfu /fish infected group, the epizootic haemorrhagic ulcer was developed, and haemorragic red sports were formed around abdomen and fins and its died (40%). Total cell protein peptide bands of the A. salmonicida EL-1 were presented betweeon 11.8~102 Kd in molecular weight by the electrophoretic analysis and appeared 28 bands in all. Drug sensitivity of atypical A. salmonicida EL-1 strain was sensitivity to chlorampenicol, gentamicin, kanamycin, streptomycin and sulfamethoxazole /trimethoprim and intermidiate to ampiclin and neomycin resistant to cephalotin, erythromycin, lincomycin and tetracycline.