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Echinochasmus japonicus

Disease. Echinochasmiasis

Geographic distribution. Human cases were found from Far-Eastern countries including Korea, Japan and China.

Infection rate. Prevalence in human is not known well.

Life cycle. The first intermediate hosts are Parafossarulus (Bulimus) striatulus japonicus, and P. manchouricus. The second intermediate hosts are at least 24 kinds of fresh or brackish water fishes such as Pseudorasbora parva, Plecoglossus altivelis, Zacco platypus, Carassius carassius and Acanthogobius flavimanus, as well as the tadpoles of Rana rugosa. Animal definitive hosts are various kinds of birds and mammals in nature: Gallus domesticus, Anas platyrhynchos var. domestica, Nycticorax nycticorax and Milvus migrans lineatus, and stray dogs.

Morphology. The adult worms measure 0.5-1.0 mm long and wide up to 0.3 mm. The body is elongated, foliate, with lateral edges of the forebody curved ventrally. The head collar is prominent, with a row of 12 spines on each side; ventral spines in two alternating rows, dorsal spines in a single row. The cuticle is spineous. The testes are directly tandem, and cirrus sac is ellipsoidal, and is situated just behind the bifurcation of the intestine. The ovary is ovoid or elliptical and situated on posterodextral to acetabulum. The vitellaria extend from the preacetabular level to the posterior extremity. The uterus is short. The eggs are broad, oval with thin shell, tiny operculum, inapparent abopercular wrinkle, and 76-87 by 52-63 mm in size.

Pathology and clinical symptoms. Most of the recorded human cases were lightly and chronically infected. In such cases no significant symptoms were found. However, heavily infected cases suffered from digestive symptoms or signs, such as abdominal discomfort, diarrhea and anorexia.

Diagnosis. Diagnosis is made by finding the eggs from the feces. The eggs require differentiation from another intestinal flukes.

Prevention. In endemic areas, raw or insufficiently cooked tadpoles or freshwater fishes should be avoided.

Treatment. Praziquantel (Distocide®) as a single 10 mg/ kg dose taken at bedtime.
Jong-Yil Chai

Jong-Yil Chai

Metacercariae of Echinochasmus japonicus from the gill of tadpole, which was experimentally infected with cercariae.

Woon-Mok Sohn

Metacercariae of E. japonicus isolated from Pseudorasbora parva.

Woon-Mok Sohn

E. japonicus recovered from an experimentally infected dog. Semichon's acetocarmine stained.

Woon-Mok Sohn

E. japonicus recovered from a cat. Semichon's acetocarmine stained.

Woon-Mok Sohn

A species of freshwater fish, Pseudorasbora parva, a second intermediate host for Clonorchis sinensis and Echinochasmus japonicus.

Jong-Yil Chai

Parafossarulus manchoricus : first intermediate host of Echinochasmus japonicus

PR Chung/YK Park