The colour carp with the so-called Epistylis Disease which were sent from Niigata Colour-Carp Research Institute to our laboratory were submitted to study the causative organism and the way of treatment. Red spots and / or supprative wounds amounted to 5 or more per fish were present on the body surface of the diseased fish. The red spots showing haemorrhagic swelling were 5-20 mm in diameter size. A large number of rod bacteria was present in all of the wounds, and also water molds and Epistylis like bell animalcula were found in several wounds, occasionally. Two strains of gram-negative bacteria (strain A and B) which were virulent to goldfish were isolated from the wounds. The strain A, Aeromonas like, was a major bacterium, and the strain B of a minor bacterium differed from the member of Aeromonas or Vibrio. Both strains were sensitive to nifurpirinol, and rather resistant to tetracycline and malachite green. The majority of red spots and wounds disappeared within 7 days following the continued bathing in 0.05 ppm of nifurpirinol. From the results obtained, it was considered that Aeromonas like bacterium participated as a causative organism in this case.
Histopathological observations were made on granuloma caused byAcanthocephalain the cultured rainbow trout(Salmo gairdnerii irideus).Acanthocephalawere found to be parasitic on the most part of the lumen of the pyloric ceacum and intestine except the stomach. These parasites intruded into the mucosa of the both organs by their hooks of proboscis, and consequently chronic catarrhal enteritis was demonstrated on the digestive organs mentioned above. Acanthocephalan infections were characterized by granulomatous proliferation. The granuloma was formed in the submucosa of the pyloric ceacum and intestine in which the parasite had already invaded, and granulomatous reaction was evidently recognized to be carried out only around the worm. In the present observation, the granuloma appeared to consist of three zones, epithelioid cells, fibroblasts, and fibrous tissue in which acidophilic granular cells were recognized to be mainly interspersed. Acidophilic granular cells infiltrated not only in the granuloma but also in the epithelial layer of the pyloric ceacum and intestine. These cells were considered as the wandering cells derived from the tissue.