Tetrahymena corlissi , a free-living protozoan, apparently caused the death of large numbers of guppies ( Poecilia reticulatus ) and occasionally other fishes, in aquaria and hatcheries at several locations. Apparently the disease occurs when the fish and protozoan populations are both at a high level of density. The signs include white spots and epidermal damage. Histologically, T. corlissi could be seen in skin, muscle, and viscera; in some there was marked inflammation, in others there was little tissue reaction. A key is presented for the identification of invasive fish ciliates: Chilodonella , Hemiophrys , Ichthyophthirius , Ophryoglena , and Tetrahymena .

Journal of Parasitology↗

USGS1975

Variation in response of channel catfish to Henneguya sp. infections (Protozoa: Myxosporidea)

Infections in channel catfish ( Ictalurus punctatus , Rafinesque) induced by the sporozoan Henneguya (Protozoa: Myxosporidea) result in seven known and diverse disease manifestations. Most outstanding is an interlamellar branchial form responsible for significant losses among immature catfish, and a unique papillomatous form. The question of whether or not the species of Henneguya involved in these cases is H. exilis remains to be resolved.

Journal of Wildlife Diseases↗

USGS1975

Whirling disease (Myxosoma cerebralis): Control with ultraviolet irradiation and effect on fish

Water contaminated by Myxosoma cerebralis was disinfected with ultraviolet irradition to control whirling disease. Irradiation at 18,000 microwatt seconds/cm 2 (MWS/cm 2 ) reduced infectivity of M. cerebralis by 31-86% and 27,650 MWS/cm 3 reduced infectivity by 86-100%, even in the presence of a small amount of silt.

Journal of Wildlife Diseases↗

USGS1974

Disinfection of contaminated water by ultraviolet irradiation, with emphasis on whirling disease (Myxosoma cerebralis) and its effect on fish

Rainbow trout fry developed whirling disease upon exposure to water contaminated with Myxosoma cerebralis. When similarly contaminated water was irradiated with 2537 Angstrom units of ultraviolet light at dosages of 35,000, 43,000, and 112,000 microwatt sec/cm 2 , infection of fry was prevented. The minimum effective dosage was not determined in the present experiments. High mortality and a 61% growth inhibition of survivors occurred in the infected fry.

Transactions of the American Fisheries Society↗

USGS1973