Prevalence and histopathology of Trichogaster pectoralis harbouring metacercaria of Clinostomum piscidium (Southwell and Prashad, 1918) in central Thailand

Abstract

The aim of this study was to identify the digenea in abdominal cavity of Trichogaster pectoralis from two fish farms in Ban Paew District, Samutsakorn Province, Central Thailand, and to investigate the prevalence, intensity and pathological alterations caused by fluke in the host fish. Two hundred and seventy three 8 to 10- month-old T. pectoralis were obtained from two farms (60 females and 75 males from the first and 63 females and 75 males from the second). Their total length and body weight were measured. Metacercariae of Clinostomum piscidium were identified in the body cavity of T. pectoralis. The parasites were found either free or attached to adipose tissue and external surface of visceral in abdominal cavity of the infected fish. The prevalence and parasite intensities were greater in the females than in the males collected from both farms (p<0.01). The infected fish appeared starved with significantly decreased body weight when compared to the uninfected fish (p<0.01). Gross pathological findings revealed a few white migratory tracks on hepatic surface. Histologically, the track appeared as central hepatic and pancreatic cells necrosis and hemorrhage surrounded by a layer of macrophages and epithelioid cells, surrounded by a rim of lymphocytes, eosinophilic granular cells and fibroblasts. Eosinophils were in close contact with the fluke's tegument. The infection with this metacercaria caused hepatic tissue damage which, in turn, interrupted the hepatic metabolism, causing growth retardation and a decrease in body weight of the fish hosts.