Larval Gnathostomes and Spargana in Chinese Edible Frogs, Hoplobatrachus rugulosus, from Myanmar: Potential Risk of Human Infection

Abstract

Chinese edible frogs, Hoplobatrachus rugulosus, were examined to estimate the potential risks of human gnathostomiasis and sparganosis in Myanmar. A total of 20 frogs were purchased in a local market of Yangon and examined with naked eyes and the artificial digestion method after skin peeling in June 2018 and June 2019. Larvae of gnathostomes and Spirometra (=spargana) were detected in 15 (75.0%) and 15 (75.0%) frogs with average intensities of 10.5 and 6.3 larvae per infected frog, respectively. Gnathostome larvae were 2.75-3.80 (av. 3.30) mm long and 0.29-0.36 (0.33) mm wide. They had a characteristic head bulb with 4 rows of hooklets, a muscular long esophagus, and 2 pairs of cervical sac. The mean number of hooklets were 41, 44, 47, and 50 on the 1st, 2nd, 3rd, and 4th row, respectively. Collected spargana were actively moving, particularly with the scolex part, and have ivory-white color and variable in size. Conclusively, it has been first confirmed that Chinese edible frogs, H. rugulosus, are highly infected with larval gnathostomes and spargana in this study. Consuming these frogs is considered a potential risk of human gnathostomiasis and sparganosis in Myanmar.

Larval Gnathostomes and Zoonotic Trematode Metacercariae in Fish from a Local Market in Yangon City, Myanmar

“…The mean number of hooklets was 40, 43, 46, and 48 on the 1st, 2nd, 3rd, and 4th row, respectively. They were more or less smaller than those (from swamp eels and Chinese edible frogs) of previous studies in Myanmar [ 21 , 23 ].…”

“…The mean number of hooklets was 40, 43, 46, and 48 on the 1st, 2nd, 3rd, and 4th row, respectively. They were more or less smaller than those (from swamp eels and Chinese edible frogs) of previous studies in Myanmar[21,23].More than 8 species, i.e., Opisthorchis viverrini, Haplorchis taichui, H. pumilio, H. yokogawai, Centrocestus spp., Stellantchasmus falcatus, Pygidiopsis cambodiensis, and Procerovum sp., of ZTM were detected. The metacercariae of O. viverrini were found in 10 (2.9%) out of 349 fish in 5 species (38.5%), i.e., C. lucius, A. testudineus, Thynnichthys thynnoides, C. striata, and Puntioplites sp.…”

“…More than 42 cutaneous cases and over 10 ocular cases have been reported since the first case in 1960 [24][25][26][27][28]. The infection status with larval gnathostomes were investigated in fish and frog hosts 4 times in Myanmar [19][20][21]23]. Chai et al [19] The endemicity of O. viverrini metacercariae (prevalence below 3.0%; intensity of infection about 17 per fish infected) was very low like in Sohn et al [16].…”

“…More than 42 cutaneous cases and over 10 ocular cases have been reported since the first case in 1960 [ 24 – 28 ]. The infection status with larval gnathostomes were investigated in fish and frog hosts 4 times in Myanmar [ 19 – 21 , 23 ]. Chai et al [ 19 ] found 2 AdL 3 of G. spinigerum from 2 catfish in the examination of 10 freshwater fish in 3 species, i.e., Parasilurus sp., Tilapia sp.…”

“…Chai et al [ 21 ] detected a total of 401 G. spinigerum AdL 3 in 33 (89.2%) out of 37 Asian swamp eels purchased in a local market of Yangon. Recently, Chai et al [ 23 ] also detected 158 larval gnathostomes in 15 (75.0%) out of 20 Chinese edible frogs, Hoplobatrachus rugulosus , from a local market of Yangon. In this study, larval gnathostomes were found in 58 (16.0%) out of 362 fish in 6 species, i.e., C. lucius , C. striata , A. testudineus , C. macrolepis , H. kemratensis , and unidentified snakehead, and the forest snakehead, C. lucius , was the most prevalent fish host.…”