No Opisthorchis viverrini metacercariae were found in the analyzed fish, only the species from the Heterophyidae families. While the public health and food safety issues with Opisthorchis viverrini are well known, there is less information available about the effects of Heterophyidae families on human health. There have been many reports of human infections of Heterophyidae families in the North, Northeast and Central of Thailand ( Waikagul and Radomyos, 2004 and Sripalwit et al., 2003) where the clinical manifestations of intestinal flukes are less well described. The mechanisms of pathogenesis are unclear but it has been reported as causing intestinal irritation accompanied by colicky pain and mucous diarrhea, with the production of excess mucus and superficial necrosis of the mucous coat. However, some of the heterophyid flukes possibly wander in the deep layers of the intestinal wall and become imprisoned and die (Sripalwit et al., 2003). Special cases reported that the eggs of the intestinal flukes including Stellantchasmus falcatus, Haplorchis spp. can cause significant pathology in human ( WHO, 1995).
The result reveals the low risk for FZT in cultured Nile tilapia from cage and pond aquaculture systems. However, the high prevalence of FZT in local wild-caught fish indicates a high potential for spillover from wild reservoir hosts and underscores the need for vigilance and good management practices to make aquaculture systems bio-secure