Outbreak of trypanosomiasis in net-cage cultured barramundi, Lates calcarifer (Perciformes, Latidae), associated with Trypanosoma epinepheli (Kinetoplastida) in South China Sea

摘要

The barramundi or Asian Sea bass (Lates calcarifer) is of high economic importance for aquaculture worldwide. The present work report a trypanosomiosis of net cage reared barramundi in South China Sea and identified Trypanosoma epinepheli to be the causative agent, which expand the host range of this blood flagellate. This epizootic trypanosomiosis was of distinctly seasonal pattern which occurred from middle-to-late March to middle-to-late May, when water temperature ranged from 21 to 28 degrees C and salinity from 30-33ppt. The infected fish showed typical clinical symptoms of fish trypanosomiosis, including loss of appetite, lethargy, slight emaciation, slightly darken body, swimming lonely and restlessly at the water surface. Mild anemia in gills and remarkable splenomegaly were observed after necropsy. Histopathological investigations showed distinct pathological changes in gill, brain, liver, spleen and kidney, almost consistent with the previous report. This study is the first report of trypanosomiasis in this increasingly important mariculture fish in China.