ABSTRACT
@#Opisthorchiasis is endemic in parts of Southeast Asia, including the northern and northeastern regions of Thailand. In these regions, the transmission by fish intermediate hosts has received little attention. We investigated the intensity of Opisthorchis viverrini metacercariae (OV MC) in wild cyprinid fishes from five districts within the Nakhon Phanom Province, Northeast Thailand. Fishes were procured from local markets in five districts throughout three different seasons (hot, rainy and cold) between February 2018 and January 2019. The samples were identified, counted and weighed before metacercariae detection was performed via the artificial digestion method. A total of 2,149 freshwater fishes, representing 20 species were collected. The fish most commonly contaminated with OV MC were Anematichthys repasson and Hampala dispar. The intensity of OV MC in Nakhon Phanom was 0.23 OV MC/fish and varied among districts, ranging from 0.07 to 0.52. A low intensity of OV MC/fish (defined as <1 cyst) was found in all three different seasons in the Nakhon Phanom Province; hot season (0.55), cold season (0.22) and the rainy season (0.13). The intensity of OV MC/fish was moderate (defined as >1 cyst) in the Renu Nakhon district (2.5) in the hot season. By fish species, H. dispar yielded the highest, with a moderate intensity of 2.1. In natural freshwater cyprinid fish in Nakhon Phanom, OV MC infection is endemic with intensity rates varying according to district, season and fish species.
ABSTRACT
To increase public health awareness for prevention of opisthorchiasis caused by eating raw freshwater fish, the distribution and abundance of Opisthorchis viverrini metacercariae (OV MC) was investigated in freshwater fish obtained from 20 provinces in northeastern Thailand between April 2011 and February 2012. A cross-sectional survey was conducted on 12,890 fish consisting of 13 species randomly caught from 26 rivers, 10 dams, and 38 ponds/lakes. Fish, were collected in each of the rainy and winter seasons from each province. Fish were identified, counted, weighed, and digested using pepsin-HCl. Samples were examined for OV MC by a sedimentation method, and metacercariae were identified under a stereomicroscope. OV MC were found in 6 species of fish; i.e., Cyclocheilichthys armatus, Puntius orphoides, Hampala dispar, Henicorhynchus siamensis, Osteochilus hasselti, and Puntioplites proctozysron from localities in 13 provinces. Among the sites where OV MC-infected fish were found, 70.0% were dams, 23.7% were ponds/lakes, and 7.7% were rivers. The mean intensity of OV MC ranged from 0.01 to 6.5 cysts per fish (or 1.3-287.5 cysts per kg of fish). A high mean intensity of OV MC per fish (>3 cysts) was found in 5 provinces: Amnat Charoen (6.5 cysts), Nakhon Phanom (4.3), Mukdahan (4.1), Khon Kaen, (3.5) and Si Sa Ket (3.4). In conclusion, OV MC are prevalent in natural cyprinid fish, with the infection rate varying according to fish species and habitats.