Trypanosomes and dactylosomes from the blood of fresh-water fish in East Africa

1. Trypanosomes were found in the blood of thirty-five of seventy-two fish of five genera (chiefly Tilapia spp.) from Lakes Victoria and George, Uganda.2. The trypanosomes, which were never numerous in the blood, showed two morphological forms—small (22–44μ. long) and large (45–65μ). No significant differences were observed between the trypanosomes from the different species of fish, and all the trypanosomes seen are provisionally identified as Trypanosoma mukasai Hoare, 1932.3. Crithidia were found in the gut of a glossosiphoniid leech which had been removed from a fish; although suggestive, this cannot be taken as conclusive evidence that leeches of this family are vectors of T. mukasai.4. The taxonomy of the trypanosomes of African fresh-water fish is reviewed, and it is concluded that only the following species should be regarded as valid at present: T. toddi Bouet, 1909, T. mukasai Hoare, 1932, and T. tobeyi Dias, 1952.5. Dactylosoma mariae Hoare, 1930, was found in the blood of thirty-six of the seventy-two fish examined. Merozoites, schizonts and gametocytes of this small unpigmented parasite were observed within erythrocytes. No developmental stages were found in certain viscera of two infected fish.