The parasitic ciliate Ichthyophthirius multifiliis is a common protozoan pathogen of freshwater fishes 1 and etiological agent of “Ich” or “White Spot Disease” 2 which has caused economic losses in ornamental fish culture in the tropics 3-5. It is the main parasitic threat to freshwater fish 6,7 and commonly found in gills and dermis of fish 3. Trophozoite or feeding stage of Ichthyophthirius is found within the epidermis of fish where it may reach up to 1 mm in diamater and is seen as a characteristic white spot from which the disease takes its name 7 . Ichthyophthirius is easily recognized in skin scrapings by its size and characteristic horse-shoeshaped macronucleus 7 and the center of the adult organism has a C-shaped nucleus 8. The parasite caused problems during the warmer seasons 6 and infections
fall when the water temperatures are between 18 and 25°C 1. It is an obligate parasite with a life cycle that consists of fish associated and free-swimming stages referred to as trophonts and theronts, respectively 9-11 .
In this report, we were described macroscopic and microscopic findings in a Black Tetra (Gymnocorymbus ternetzi) naturally infected with Ichthyophthirius multifiliis