養殖ウナギのChondrococcus columnaris感染症に関する研究-II : 養殖ウナギの鰓病とC. columnarisの関係

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1) In a previous study it was clarified by experiments that in eels Chondrococcus columnaris infection results in a partial loss of the gill filaments, which is known as a symptom peculiar to the so-called gill disease of pond-cultured eels. In the present study the causative relationship between the gill disease and the bacterium was investigated with eels in acutual eelponds at Yoshida, Shizuoka Prefecture. 2) Comparisons made during a gill disease prevailing season, between moribund and apparently healthy eels, revealed that although healthy eels too commonly had affected gill filaments, often harbouring C. columnaris on the gills and sometimes agglutinins to the bacterium, moribund eels generally had more seriously damaged gills and more frequently had the agglutinins, while there was no definite difference between the two in the rate at which the organism was isolated from the gills. 3) A bimonthly investigation of healthy eels revealed that (1) partial loss of gill filaments were observed throughout the year and the average degree of loss of gill filaments was larger in the warm months and minimum in February; (2) C. columnaris was isolated from the gills in a part of the fishes examined in June, August and October, but not in December to April; and (3) the percentage of fishes having the agglutinins was higher in April and June and low in August to February, being minimum in February. 4) No other germs nor parasites which were considered to be responsible for the gill disease were detected. 5) From these results it is suggested that (1) the activity of C. columnaris in eel-ponds starts about in April, reaches its height in summer and comes to an end in October; (2) the process of development of gill lesions may be different according to the virulence of the bacteria and environmental factors, including competitive bacteria. In some cases the bacteria cause serious damage to the gills leading to speedy death, while in others the bacteria once grown on the gills disappear, leaving a partial loss of gill filaments in the affected areas. 6) The possibility that slight injuries caused by food particles passing over the gills may enable C. clumnaris to obtain a foothold on the gills is also suggested.
公益社団法人日本水産学会の論文

養殖ウナギのChondrococcus columnaris感染症に関する研究-II : 養殖ウナギの鰓病とC. columnarisの関係

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