病例報告：養殖淡水石斑魚（Cichlasoma managuense）錐蟲病（Trypanosomiasis）

Abstract

An outbreak disease occurred in a pond raising about 2,000 freshwater fish (Cichlasoma manaquense) from an aquaculture farm in southern Taiwan. The clinical signs of affected fish showed anorexia, black discoloration of body surface, sluggish swimming and weakness before death. The total morbidity was about 10% and fifteen fish were sent for necropsy. In gross, all examined fish had black discoloration on the body surface; also, yellowish liver (14/15), splenomegaly (14/15), pale gill (12/15), and eye cloudiness with protrusion (10/ 15) were noticed. Histopathologically, hyperplasia of reticuloendothelial cell associated with hemosiderin deposition was found in the spleen, and the liver showed massive hepatical fatty change. Moreover, trypanosoma penetrated every blood vessel of all visceral organs. Hematological examination revealed mild to severe anemia with various degrees of reduction in total erythrocyte count, packed cell volume, and haemoglobin concentration. In addition, numerous trypanosoma were found in the examined blood film, and the protozoa were confirmed as trypomastigote form stage of trypanosoma through scanning electromicroscopic study. From the results, it was concluded that the outbreak disease was caused by Trypanosoma sp. This is the first case report of freshwater fish trypanosomiasis found in Taiwan.