Abstract
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.
