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Paragonimus westermani (Japanese lung fluke or oriental lung fluke) is the most common species of lung fluke that infects humans, causing paragonimiasis. [2] Human infections are most common in eastern Asia and in South America. Paragonimiasis may present as a sub-acute to chronic inflammatory disease of the lung. It was discovered by Dutch ...
The lung fluke encysts within the tissue of crustaceans until the crustacean is consumed by humans or other animals. Once the fluke has been ingested, enzymes within the digestive tract of the consumer break down the parasitic cysts. The immature parasite continues to mature within the lungs of its new host, feeding on its intestine, and lay eggs.
Paragonimiasis is a food-borne parasitic disease caused by several species of lung flukes belonging to genus Paragonimus. [4] Infection is acquired by eating crustaceans such as crabs and crayfishes which host the infective forms called metacercariae, or by eating raw or undercooked meat of mammals harboring the metacercariae from crustaceans.
In the intestine, the parasite will move into the abdomen and commonly into the lungs. In the lung, the parasites encyst and cross fertilize each other. The cyst eventually ruptures in the lungs and the eggs may be coughed up or swallowed and excreted in the feces. An egg landing in fresh water hatches and releases a ciliated miracidium.
Metagonimus yokogawai has adult flukes that parasitize the small intestine and causes inflammation. [5] This species was discovered by Fujiro Katsurada with egg samples from Japan and Taiwan [6] With this discovery, he was able to make a new genus of trematodes that this new parasite would fall under [6] The size of these eggs are about 29 μm. [7]
As the larvae travel towards the respiratory system, they mature, and by the time they reach the lungs, they are full adults. [10] Once they reach the lungs the females lay eggs and once they hatch the new larvae travel up the windpipe to be swallowed and then expelled, repeating the cycle. [ 8 ]
Fasciola hepatica, a species of liver flukes, has a higher incidence rate in children and females, with more cases of lung fluke and intestinal trematodiases in children. [5] Cases of liver and lung fluke trematodiasis are frequent due to the length of time the trematode can live in host organisms, and increased chances of reinfection. [9]
The metagonimiasis-causing flukes are one of two minute flukes called the heterophyids. Metagonimiasis was described by Katsurasa in 1911–1913 when he first observed eggs of M. yokagawai in feces (date is disputed in various studies). M. takahashii was described later first by Suzuki in 1930 and then M. miyatai was described in 1984 by Saito.