TREMATODE METACERCARIAE INFECTION IN CYPRINOID FISH FROM UBOLRATANA RESERVOIR, NONG BUA LAM PHU PROVINCE, THAILAND

Abstract

Background: Fish-borne trematode species are associated with public health problems. Metacercariae is a parasitic infective stage that is transmitted to humans through consumption of traditional dishes containing raw cyprinoid fish. Liver fluke infection is one of the factors that can lead to cholangiocarcinoma or bile duct cancer. 

Materials and Methods: In this study, trematode metacercariae in cyprinoid fish were identified. All fish were obtained from Ubolratana Reservoir in Nong Bua Lam Phu province, Thailand, from June to September 2019. A total of 521 cyprinoid fish samples were collected and analysed. The fish samples were digested in a 0.25% pepsin-HCl solution and filtered through various sized sieves. The metacercariae were observed under stereo and compound light microscope.

Results: 1,998 metacercariae in seven fish species were identified using stereo and compound microscopy. Hampala dispar was infected with the highest mean intensity of metacercariae (52 Mc/fish) whereas Puntius sp. showed the lowest mean intensity (0.24 Mc/fish). The trematode species, Haplorchis pumilio, presented the largest proportion in total fish infected with metacercariae (44.32%) followed by Opisthorchis viverrini (25.52%), Haplorchis taichui (12.44%) and Haplorchoides spp. (1.73%).

Conclusions: The results of our study indicate the presence of contaminated fish in Ubolratana Reservoir. This is a caution for villagers to avoid uncooked fish dishes. The mean intensities of metacercariae were calculated yielding interesting results. Therefore, a study of the prevalence of metacercariae infection will be conducted in 2020 by our research team.

Keywords: Metacercariae, Cyprinoid fish