Echinostoma macrorchis Metacercariae in Cipangopaludina chinensis malleata from Xiengkhuang Province, Lao PDR and Morphologies of Adults from Experimental Animals

We identified the echinostome metacercariae in Chinese mystery snails, Cipangopaludina chinensis malleata, from Xiengkhuang Province, Lao PDR with morphologies of adult worms recovered. Total 20 snails were examined with artificial digestion method and then the collected metacercariae were orally infected to a mouse and a rat. Adult worms recovered from experimental animals were observed with a light microscope and a SEM. The metacercariae were round, 125×123 μm in average size, with a moderately thick cyst wall, collar spines distributed in the head collar and excretory granules in 2 canals of excretory tube. Adult flukes (3-week-old in a rat) were elongated, ventrally curved and 5.310×1.023 mm in average size. Head collar distinct, bearing 43 collar spines with 5 end group ones on each side. Oral sucker subterminal, prepharynx very short, pharynx well developed, and esophagus relatively short. Cirrus sac well developed, with a saccular seminal vesicle, and ventral sucker very large. Ovary round and on the median line of the body. Testes tandom and elongated. Eggs operculated, elliptical and 90×57 μm in average size. In the SEM observation, the head crown prominent, with 43 collar spines resembled with horns of younger stag. Scale-like tegumental spines were densely distributed on the surface between the head collar and ventral sucker, and their densities were decreased posteriorly. Conclusively, the metacercariae detected in C. chinensis malleata from Lao PDR were identified as those of Echinostoma macrorchis based on the morphological characteristics of adult worms.

Echinostoma macrorchis (Digenea: Echinostomatidae): Metacercariae in Cipangopaludina chinensis malleata Snails and Adults from Experimental Rats in Korea

A survey was performed to know the infection status of echinostome metacercariae in Cipangopaludina chinensis malleata snails from Korea. Total 75 snails collected in 5 localities, i.e., Imsil-gun, Jeollabuk-do, Hwasun-gun and Shinan-gun (Aphae and Jido), Jeollanam-do, and Jinju-si, Gyeongsangnam-do, were examined for metacercariae by the artificial digestion method. Infection rates of metacercariae were 80.0%, 66.7%, 100%, 60.0%, and 73.3%, and their densities were 39, 32, 183, 19, and 30 per snail infected, respectively. The metacercariae were round, 105–118×105–118 μm in size, with a thin cyst wall, collar spines on the head collar, and excretory granules in 2 canals of excretory tube. Adult flukes were elongated, ventrally curved, and 5,167×939 μm in average size. Head collar distinct, bearing 45 collar spines with 5 end groups on each side. Oral sucker subterminal, pharynx well developed, and esophagus somewhat short. Cirrus sac well developed, with a saccular seminal vesicle, and ventral sucker very large. Ovary elliptical and on the median line of the body. Testes tandem and slightly lobed. Eggs operculated, elliptical, and 90–103×55–60 μm in size. By scanning electron microscopy, the head collar was prominent with 45 collar spines resembling horns of younger stags. Scale-like tegumental spines were densely distributed on the body surface between the head collar and ventral sucker. Conclusively, it has been first confirmed that the life cycle of E. macrorchis is indigenously maintained in Korea, and C. chinensis malleata snails are popularly infected with the metacercariae of this echinostome.

Echinostoma macrorchis in Lao PDR: Metacercariae in Cipangopaludina Snails and Adults from Experimentally Infected Animals

The echinostome metacercariae encysted in Cipangopaludina sp. snails that were purchased from a market in Vientiane Municipality, Lao PDR, were identified as Echinostoma macrorchis (Digenea: Echinostomatidae) through recovery of adult flukes after experimental infection to rats and a cat. The metacercariae were round, 113-128 (121)x113-125 (120) microm, having a thick cyst wall, a head collar armed with collar spines, and excretory granules. The adult flukes recovered from the rats and cat at day 14 and 30 post-infection, respectively, were elongated, ventrally curved, and 3.9-6.3x0.7-1.1 mm in size. The head collar was distinct, bearing 43-45 collar spines with 5 angle spines on each side. Two testes were large (as the name implies), tandem, and slightly constricted at the middle, with irregular margins. Eggs were operculated, ovoid to elliptical, and 88-95x56-60 microm. In scanning electron microscopy, the head collar was prominent, with 43-45 collar spines. Scale-like tegumental spines were densely distributed on the ventral surface between the oral and ventral suckers. Sensory papillae were distributed mainly on the tegument around the 2 suckers. It is confirmed that E. macrorchis is distributed in Lao PDR using Cipangopaludina sp. snails as the second intermediate host.