Distribution patterns of opisthorchis viverrini and haplorchis taichui infections in two villages of sava nnakhet province, lao PDR

Abstract

The liver fluke, Opisthorchis viverrini, and the minute intestinal fluke, Haplorchis taichui, are prevalent in many Asian countries. In this study, the pattern of infection with Opisthorchis viverrini and Haplorchis tachui in Lahanam and Thakhamrien Villages (Savanakhet Province, Lao PDR) was analysed in two cross sectional investigations. Intermediate hosts fishes acquired in the study area were also analysed. Postanthelminthic treatment positivity rates for expelled worms were 170 (82.1%) for H. taichui and 65 (31.4%) for O. viverrini from a total of 207 participants; these 2 species co-existed in the study villages. Opisthorchiid egg findings initially increased with age, but decreased again from age 30 years. However, when each parasite was analysed separately, H. taichui infection reached a plateau among the age group > 20 years, and the O. viverrini infection rate was highest in the age group 21-30 years, with decreasing infection rates after age 30. Our results indicate that fish-borne trematode infections in particular are more prevalent among adults. Examination of fish intermediate hosts found O. viverrini metacercariae in only 6 species of the 35 examined, and these were mostly found during November. At this time, many farmers stay in the ricefields and obtain their food nearby, including intermediate-host fish, and may be at greater risk of O. viverrini infection. By contrast, H. taichui metacercariae were found in 3 species of fish, and only from the market, which means that anyone could consume them and become infected. If people working in ricefields limit the fish species they consume or avoid consuming raw fish around November, it may help reduce the risk of O. viverrini infection.