case report and treatment of hole in the head in oscar, astronotus ocellatus

hole in the head is one of the important diseases of cichlid fishes that caused by heximita or spironucleus infections. in december 2007, a diseased oscar was referred to the veterinary hospital, shahid chamran university, ahvaz, iran. infected fish showed an initial loss of appetite, exophthalmia, darkness of skin followed by holes appearing on the head surface and a complete refusal to feed. for detecting the hexamitid flagellates, investigation was undertaken by taking the smear from the holes in head. heavy flagellate infection was detected in the smears and the parasite recognized as hexamita according to the shape, type of movement and size of the parasite with photomicroscopy directly and examination of tissue squash in giemsa-stained dry smear preparations. in order to detect the bacterial infection of the lesions, the sample was taken from the holes and cultured on tsa and kept at 25°c for 24 h. large number of aeromonas hydrophila colonies were appeared on the agar after 24 h and recognized by bacteriological tests. the fish was treated with long term bath of 6 mg/l metronidazole and after 24 h, with 0.2 ppm malachite green mixed with 0.15 ppm formalin. the fish fed a balanced and vitamin enriched diet by stomach tube for several days. the fish gradually showed signs of improvement and after 10 days, the fish completely recovered.