Ciliate parasite Ichthyophthirius multifiliis causing acute mortality in tiger barb (Puntigrus tetrazona, Bleeker, 1855) and widow tetra (Gymnocorymbus ternetzi, Boulenger, 1895).

A mixed group of tiger barb (Puntigrus tetrazona) and different colored glo widow tetra (Gymnocorymbus ternetzi) were procured from Galiff street market of Kolkata, India and stocked in a glass aquarium with 250L water capacity for ornamental fish decorative purpose. After a few days of stocking, fishes were (mean weight of 1.8 ± 0.5 g and mean length 5.0 ± 0.3 cm) found severely infected with white spot disease. Initially, the manifestation was clearly observed in Tiger barb followed by widow tetra with clinical signs of white spot, loss of fin, complete loss of gill filaments, and anorexia. The causative agent was identified as protozoan ciliate parasite Ichthyophthirius multifiliis, by wet mount preparation. The histopathological observation of infected fish skin tissue depicts that epidermis were severely damaged and presence of trophozoite parasite in dermis near the blood vessels. Molecular characterization of the parasitic pathogen was carried out by partial18s rDNA sequencing and the obtained sequences were showing 100% similarity with previously reported Indian I. multifiliis sequence.