Histopathology of Kabatana arthuri (Microspora) infection in sutchi catfish, Pangasius sutchi

The microsporidian Kabatana arthuri (Lom, Dykova et Shaharom, 1990) induced severe regressive changes in trunk muscles of Pangasius sutchi (Fowler) fr om Thailand. Necrotic changes developed in muscle fibres around the develop mental stages and on the periphery of giant aggregates of spores. The main feature of the host defence reaction was the phagocytic activity of macroph ages. Inflammatory reaction was only exceptionally observed. Spore-laden ma crophages were found in various tissues and organs; their infiltration in e pidermis including its outermost layers may effectively enhance the spread of infection while the hosts still live.