A novel fluke species, morphologically resembling Opisthorchis viverrini, was discovered in the Yangon Region, Myanmar. Metacercariae were found in the muscle tissue of 2 snakehead fish species, Mi and Channa striata. The metacercariae were elliptical (average 165×122 μm, n=10), having 2 suckers and a large excretory bladder. Experimental infection of a hamster resulted in the recovery of adult flukes from the bile ducts at day 50 post-infection. Adult flukes were lanceolate, with dimensions of 3.8–6.0 (average 5.1) mm by 1.1–1.2 (1.2) mm (n=10). Morphological characteristics included an oral sucker slightly smaller than the ventral sucker, a long uterus not extending anterior to the ventral sucker, vitelline follicles reaching the anterior ovary level, and 2 deeply lobed testes (4 lobes anteriorly, 5 posteriorly). Eggs were ovoid to elliptical, measuring 26.3–27.5 (26.9) μm in length and 13.8–15.0 (14.6) μm in width (n=10). Despite the close morphological resemblance to O. viverrini, our specimens displayed significant differences, including a more spiraled seminal vesicle, a longer uterus occupying 50%–60% of the body length, a less distinct grouping of vitelline follicles (forming 7–8 groups on each side in O. viverrini), vitelline follicles restricted to the ovary level (beyond the posterior end of the ovary or at anterior testis level in O. viverrini), and smaller metacercariae. We tentatively categorize our specimens as an O. viverrini-like liver fluke potentially parasitizing mammals or birds, highlighting the need for further research. Rigorous molecular analyses and identification of natural definitive hosts are essential to clarify the taxonomic status of this novel parasite.
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Toward resolving cryptic diversity in opisthorchiid flukes: Molecular clarification of an Opisthorchis viverrini-like parasite in Myanmar is urgently needed Schawanya Kaewpitoon Rattanapitoon, Chutharat Thanchonnang, Nathkapach Kaewpitoon Rattanapitoon Parasites, Hosts and Diseases.2025; 63(3): 284. CrossRef
The Chinese edible frogs, Hoplobatrachus rugulosus (n=20), and the striped snakehead fish, Channa striata (n=34), were purchased from local markets in 3 administrative regions of Cambodia (Phnom Penh, Pursat, and Takeo Provinces) from May 2017 to April 2019, and their infection status with Gnathostoma sp. larvae was investigated. The frogs and fish were transported to the laboratory with ice and examined using the artificial digestion method. Advanced 3rd-stage larvae (AdL3) of Gnathostoma spinigerum, 24 in total number (1-6 larvae/frog), were detected from 6 (60.0%) out of 10 frogs purchased from Phnom Penh. No gnathostome larvae were detected in 10 frogs purchased from Takeo Province and 34 snakeheads from Phnom Penh, Pursat, and Takeo Provinces. AdL3 isolated from the frogs were 2.55- 3.90 mm long and 0.31-0.36 mm wide. They had a characteristic head bulb (0.081×0.191 mm in average size) with 4 rows of hooklets, a muscular long esophagus (0.950-1.230 mm long), and 2 pairs of cervical sacs (0.530-0.890 mm long). The average number of hooklets in the 1st, 2nd, 3rd, and 4th rows was 41, 45, 48, and 51, respectively. These features were consistent with G. spinigerum AdL3. By the present study, it has been first confirmed that the Chinese edible frog, H. rugulosus, from Phnom Penh serves as a second intermediate host for G. spinigerum, although their intensity of infection was not so high compared to other previously reported localities.
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To examine the infection status of freshwater fish with Gnathostoma spp. larvae in Myanmar, we purchased 15 snakeheads, Channa striatus, from a local market in a suburban area of Naypyidaw, the new capital city. Two larval gnathostomes were collected using an artificial digestion technique, and observed by a light microscope and a scanning electron microscope. The size of an intact larva was 2.65 mm long and 0.32 mm wide. The characteristic morphology of the larvae included the presence of a long esophagus (0.80 mm long), 2 pairs of cervical sacs (0.43 mm long), and a characteristic head bulb with 4 rows of hooklets. The number of hooklets in the 1st, 2nd, 3rd, and 4th row was 45, 48, 50, and 52, respectively. Based on these morphological characters, the larvae were identified as the advanced 3rd-stage larvae of Gnathostoma spinigerum. This is the first report of detection of G. spinigerum 3rd-stage larvae in the central part of Myanmar. Our study suggests that intake of raw meat of snakehead fish in Myanmar may result in human gnathostomiasis.
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