''Metagonimus yokogawai'' is a species of a

trematode Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host ...

, or fluke worm, in the family

Heterophyidae Heterophyidae is a family of intestinal trematodes in the order Plagiorchiida. Description: " Tegument covered by spines. Oral sucker not armed or armed by cyrcumoral spines. Pharynx presented. Genital synus presented. Ventral and genital suc ...

. It is a human parasite causing

metagonimiasis Metagonimiasis is a disease caused by an intestinal trematode, most commonly ''Metagonimus yokagawai'', but sometimes by ''M. takashii'' or ''M. miyatai''. The metagonimiasis-causing flukes are one of two minute flukes called the heterophyids. Met ...

. It is among a few species of ''

Metagonimus ''Metagonimus'' is a genus of trematodes, or fluke worms, in the family Heterophyidae. It is a parasite causing metagonimiasis. Species There are 8 species within the genus ''Metagonimus'' include: * '' Metagonimus hakubaensis'' Shimazu, 1999 ...

'' that cause metagonimiasis diseases (others being '' M. takahashii'' and '' M. miyatai'').

Distribution

This species occurs in Korea, China, Taiwan, Japan, Russia, Indonesia, Israel, and Spain. This species is found in areas with sweetfish, and that includes western and eastern riversides. It is basically found in places with water.

Description

''Metagonimus yokogawai'' has adult flukes that parasitize the small intestine and causes inflammation. This species was discovered by Fujiro Katsurada with egg samples from Japan and Taiwan With this discovery, he was able to make a new genus of trematodes that this new parasite would fall under The size of these eggs are about 29 μm. Evidence also suggest that this parasite was present during the Yi dynasty. Nema Fig5

Life cycle

The first intermediate hosts of ''Metagonimus yokogawai'' include freshwater snails ''

Semisulcospira libertina ''Semisulcospira libertina'' is a species of freshwater snail with an operculum, an aquatic gastropod mollusk in the family Semisulcospiridae. Widespread in east Asia, it lives in China, Taiwan, Korea, Japan, and the Philippines. In some countr ...

'', ''

Semisulcospira coreana ''Semisulcospira'' is a genus of freshwater snails with an operculum (gastropod), operculum, an aquatic gastropod mollusks in the family Semisulcospiridae. MolluscaBase eds. (2022). MolluscaBase. Semisulcospira O. Boettger, 1886. Accessed through ...

'', and ''

Semisulcospira reiniana ''Semisulcospira reiniana'' is a species of freshwater snail with an operculum (gastropod), operculum, an aquatic gastropod mollusk in the family Semisulcospiridae. Taxonomy ''Semisulcospira reiniana'' belong to the ''Semisulcospira libertina'' ...

''. The second intermediate host include freshwater fish: ''

Plecoglossus altivelis Ayu or AYU may refer to: * Ayu (given name) * Ayu sweetfish (''Plecoglossus altivelis''), a species of smelt * ''Ayu'', a local name for the African manatee * Ayu (singer) or Ayumi Hamasaki, Japanese singer * Ayu Islands, a small archipelago in I ...

'', ''

Tribolodon hakonensis The big-scaled redfin (''Tribolodon hakonensis''), also known as the Japanese dace and ugui, is a medium-sized Asian fish. First described by Albert Günther in 1877 as ''Leuciscus hakonensis'', it is the type specimen of the genus ''Tribolodon'' ...

'', ''

Tribolodon ezoe ''Tribolodon'' (Redfin dace) is a genus of cyprinid fishes found in marine and freshwater in Eastern Asia. Species There are currently 4 recognized species in this genus: * ''Tribolodon brandtii'' ( Dybowski, 1872) (Pacific redfin) * ''Tribolodon ...

'', and ''

Lateolabrax japonicus The Japanese sea bass (''Lateolabrax japonicus'') is a species of catadromous marine ray-finned fish from the Asian sea bass family Lateolabracidae which is found in the Western Pacific. In Japan this species is known as . Description The Jap ...

''. Natural definitive hosts are: dogs, cats, rats, and humans. Experminetal type hosts are:

Syrian golden hamster The golden hamster or Syrian hamster (''Mesocricetus auratus'') is a rodent belonging to the hamster subfamily, Cricetinae. Their natural geographical range is in an arid region of northern Syria and southern Turkey. Their numbers have been d ...

. Here, the life cycle of ''Metagonimus yokogawai'' will be examined, however ''

Metagonimus takahashii ''Metagonimus takahashii'' is a species of a trematode, or fluke worm, in the family Heterophyidae. It is a human parasite causing metagonimiasis. Distribution This species occurs in Japan and Korea.Chai J. Y., Darwin Murrell K. & Lymbery A. J. ...

'' and ''

Metagonimus miyatai ''Metagonimus miyatai'' is a species of a Trematoda, trematode, or fluke worm, in the family Heterophyidae. It is a human parasite causing metagonimiasis. Distribution This species occurs in Japan and Korea.Chai J. Y., Darwin Murrell K. & Lymb ...

'' follow similar life cycle pattern. All three species are

hermaphroditic In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have separ ...

and capable of

self-fertilization Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species o ...

. Embryonated eggs are passed into an aquatic environment (fresh or brackish water) each containing a fully developed larva, called a ''

miracidium The Miracidium is the second stage in the life cycle of trematodes. When trematode eggs are laid and come into contact with fresh water, they hatch and release miracidium. In this phase, miracidia are ciliated and free-swimming. This stage is comp ...

''. Development can’t proceed past this stage unless the eggs are ingested by the first intermediary host,

freshwater snail Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...

s. After the snail host ingests the eggs, miracidia emerge and penetrate the snail’s intestines. In the snail tissue, mircadia develop into sporocysts, then rediae, and finally emerge from the snail as

cercariae Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secr ...

. The cercariae then penetrate the skin or go under the scale of a fresh or brackish water fish and encyst as

metacercariae Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secr ...

in the tissue. The type of fish that serves as secondary host varies based on location. The host then becomes infected by consuming undercooked, raw, or pickled fish containing the infectious metacercariae. The metacercariae then excyst in the

small intestine The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the p ...

of the host (human, mammal or bird), and develop into adults. In the small intestine, the adults attach to the walls and develop new eggs.

References

External links

* {{NCBI taxid, 84529, ''Metagonimus yokogawai'' Heterophyidae Animals described in 1912