Low-Grade Endemicity of Opisthorchiasis, Yangon, Myanmar

We performed an epidemiologic survey of opisthorchiasis in Yangon, Myanmar. The fecal egg-positive rate of residents was 0.7%, and we recovered an adult fluke after chemotherapy and purging of an egg-positive resident. We detected Opisthorchis viverrini metacercariae in freshwater fish. We found the Yangon area to have low-grade endemicity of opisthorchiasis.


Low-Grade Endemicity of Opisthorchiasis, Yangon, Myanmar
We performed an epidemiologic survey of opisthorchiasis in Yangon, Myanmar. The fecal egg-positive rate of residents was 0.7%, and we recovered an adult fluke after chemotherapy and purging of an egg-positive resident. We detected Opisthorchis viverrini metacercariae in freshwater fish. We found the Yangon area to have low-grade endemicity of opisthorchiasis.
T he liver fluke Opisthorchis viverrini, a well-known cause of cholangiocarcinoma, is distributed predominantly in Southeast Asia countries (1,2). In Myanmar, health officials thought that opisthorchiasis might not occur because the population traditionally does not consume raw or undercooked fish. However, 2 recent reports have documented the presence of O. viverrini eggs or flukes in Myanmar (3,4). We recently observed a low-grade endemicity of O. viverrini infection among residents in the Yangon area. We also recovered an adult fluke (Appendix Figure, panel A, https://wwwnc.cdc.gov/EID/article/25/7/19-0495-App1. pdf) from an egg-positive resident and detected metacercariae in freshwater fish caught in Yangon.
Among the 14 residents positive for O. viverrini eggs (some possibly having mixed infections with minute intestinal fluke species such as Haplorchis spp.) (Table; Appendix Figure,  The procedure of the worm recovery was as described previously (5). One adult fluke that looked like a liver fluke was recovered from 1 of these 2 residents. Minute intestinal fluke species, including Haplorchis spp., were not recovered. The adult fluke (Appendix Figure, panel A) was slender (11.1 × 1.5 mm) and had a small oral sucker (0.20 × 0.29 mm), large ventral sucker (0.51 × 0.59 mm), lobed ovary, 2 lobed testes, and a well-developed uterus with numerous eggs (25 × 14 μm). We confirmed the fluke to be an adult specimen of O. viverrini.
We also examined 10 species of freshwater fish (n = 160) purchased in a local market of North Dagon to detect O. viverrini metacercariae. The fish were transported on ice to Gyeongsang National University College of Medicine (Jinju, South Korea), and examined by using the artificial digestion method (6  Opisthorchiasis is one of the most prevalent foodborne helminthiases in Thailand, Laos, Cambodia, and Vietnam (2,(5)(6)(7)(8)(9). For example, in Laos, opisthorchiasis is prevalent in the central and southern lowlands along the Mekong River, including Vientiane Municipality and Savannakhet Province, where the rates of O. viverrini egg recovery (mixed with some minute intestinal flukes) among residents along rivers were 53.3% (Vientiane) and 67.1% (Savannakhet) (5,7). In Cambodia, eastern localities (e.g., Kratie Province, 4.6% egg-positive rate) and southern localities (Kampong Cham Province, 24.0% egg-positive rate, and Takeo Province, 23.8%-47.5% egg-positive rates) along the Mekong River were found to be endemic foci (8,9). From 2 egg-positive residents in Takeo Province, 34 adult O. viverrini flukeswere recovered (10).
In our study, the O. viverrini egg-positive rate of residents in surveyed areas of Myanmar was 0.7%, much lower than the 4.6%-67.1% rates in Laos and Cambodia (5)(6)(7)(8)(9). Also, only 1 adult fluke was recovered in 1 eggpositive case, whereas 34 adult specimens were recovered in 2 residents in Cambodia (10). Thus, we concluded that the Yangon area of Myanmar has low-grade endemicity of O. viverrini.