What Is Metagonimiasis?
Metagonimiasis is a parasitic disease caused by the parasite Metagonimus yokogawai, which is part of the phylum Platyhelminthes (flatworms), of which it is part of the class Trematoda (flukes). M. yokogawai is an intestinal fluke, which are the smallest of the human flukes. M. yokogawai, in its adult form, is no longer than 2.5mm in length by 0.75mm in width.
Trematodes, or flukes, that infect humans live as adults in intestines, the biliary tract, the lungs, intestinal venules, or the genitourinary tract. Flukes are grouped and classified accoring to the main location of the adult worms in the definitive host (such as the intestine in the case of M. yokogawai). As an intestinal fluke, M. yokogawai adults live in the small intestine of the definitive host. All adult flukes are parasites of vertebrates, and all those of clinical significance (except for schistosomes) are hermaphroditic and capable of self-fertilization. All adult parasitic flukes are obligate parasites, meaning it is a parasite that cannot lead an independent nonparasitic existence, in contrast to a facultative parasite.
Flukes present a strong challenge to the protective mechanisms of the definitive host, mainly because of their small size, their complex anatomic and antigenic structure, and their remarkable abilities to evade expulsion.
Morphologically, flukes are parasitic worms that are dorsoventrally flattened, and typically bilaterally symmetric. Adults are leaf-shaped and possess two prominent suckers (one located anteriorly, also known as the "oral" sucker, and one located ventrally). These suckers help the adult anchor itself in its habitat within the organs of the definitive host.
The image below illustrates the morphology of M. yokogawai in adult form.
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