Neglected food-borne trematodiases: echinostomiasis and gastrodiscoidiasis

Abstract

In the present paper, we review two of the most neglected intestinal food-borne trematodiases: echinostomiasis, caused by members of the family Echinostomatidae, and gastrodiscoidiasis produced by the amphistome Gastrodiscoides hominis. Both parasitic infections are important intestinal food-borne diseases. Humans become infected after ingestion of raw or insufficiently cooked molluscs, fish, crustaceans, amphibians or aquatic vegetables. Thus, eating habits are essential to determine the distribution of these parasitic diseases and, traditionally, they have been considered as minor diseases confined to low-income areas, mainly in Asia. However, this scenario is changing and the population at risk are currently expanding in relation to factors such as new eating habits in developed countries, growing international markets, improved transportation systems and demographic changes. These aspects determine the necessity of a better understanding of these parasitic diseases. Herein, we review the main features of human echinostomiasis and gastrodiscoidiasis in relation to their biology, epidemiology, immunology, clinical aspects, diagnosis and treatment.

Keywords: Echinostomatidae; Gastrodiscidae; Gastrodiscoides hominis; echinostomes; food-borne trematode infections; intestinal trematodes.

Graphical abstract

Fig. 1.

Echinostoma sp.: (A) scanning electron micrographs of the cephalic collar of spines (scale bar: 100 μm); (B) adult worm (scale bar: 1 mm) and (C) unembryonated egg (scale bar: 10 μm).

Fig. 2.

Generalized life cycle of echinostomes and Gastrodiscoides hominis: adult worms inhabit the small intestine of several vertebrate hosts, including humans; eggs are voided with host feces and miracidia hatch in freshwater and actively infect the snail first intermediate host; cercariae are released by the first intermediate host and swim to locate the second intermediate host (snails, amphibians, bivalves and fishes) which they penetrate in the case of echinostomes and on aquatic plants or, alternatively, aquatic animals in the case of G. hominis; cercariae become metacercariae after encystation; metacercariae are ingested by the definitive host and excyst to become adults.

Fig. 3.

Gastrodiscoides hominis: (A) image of an upper endoscopy showing a juvenile living adult worm fixed in the mucosa of a human patient (arrow) and (B) egg isolated from the stools of a human patient (scale bar: 10 μm). Photomicrographs: courtesy of Dr Ranjit Sah.