Studies on ichthyophons disease of fishes - II : Yearling rainbow trout - Clonic infection

1. 稚魚期にイクチオフォヌスの感染が起り, その後有効な処置を施すことなく飼育し続けた魚群から満1年魚および満1.5年魚の病魚を採取し, 病理組織学的に検討した。 2. これらの年齢群の病魚では, イクチオフォヌスは全身感染を起し, 1年魚で2～3世代の, 1.5年魚で3～数世代のイクチオフォヌスを包含する肉芽腫が多発していた。またイクチオフォフスの全身的な繁殖もみられた。 3. 魚体内のイクチオフォヌスの動勢と宿主の炎症反応から, これらの年齢群の病魚は慢性感染症の状態にあると考えられた。Ichthyophonus disease had broken out among rainbow trout fry and then this fish group had been kept without effective treatment for a year. The authors observed histopathologically the prolonged diseased fish aged 12 and 18 months from this fish group. Diseased fish showed markedly stunted growth and darkish coloration, and anatomically the liver with smlall white nodules, the heart with red nodules, the tumefied spleen with its granular surface, and the markedly tumefied kidney. Histopathologically systemic dissemination and systemic proliferation of Ichthyophonus were defined. In addition to single, multinucleate-spherical bodies appeared in the various tissues, large granulomas containing two to several generations of Ichthyophonus were formed especially in the liver, kidney and speen. The number of its generation within granulomas tended to increase with the aging of the fish. The multinucleate‐spherical bodies passing generations were enclosed by very thick cell walls, but most of the well grown spherical bodies reached the pre‐germination stage and some of them were able to proliferate. From the histopathological observation on diseased fish aged from 12 to 18 months Ichthyophonus had been adding to the generations with active and continuous proliferation in the tissues and the disease prolonged from 6 months to one year became clonic