Opisthorchis viverrini
Encyclopedia
Opisthorchis viverrini, common name Southeast Asian liver fluke
, is a trematode
parasite from the family Opisthorchiidae
that attacks the area of the bile duct
. Infection
is acquired when people ingest raw or undercooked fish. It causes the disease opisthorchiasis
(also called clonorchiasis). Opisthorchis viverrini infection also predisposes the infected for cholangiocarcinoma
, a cancer of the gall bladder and/or its ducts.
Opisthorchis viverrini (together with Clonorchis sinensis
and Opisthorchis felineus
) is one of the three most medically important species in the family Opisthorchiidae.
Opisthorchis viverrini is endemic throughout Thailand
, the Lao People's Democratic Republic, Vietnam
and Cambodia
. In Northern Thailand, it is widely distributed, with high prevalence in humans, while in Central Thailand there is low rate of prevalence. The disease opisthorchiasis (caused by Opisthorchis viverrini) does not occur in southern Thailand.
.
The eggs of Opisthorchis viverrini are 30 × 12 μm in size and they are slightly narrower and more regularly ovoid than in Clonorchis sinensis. But eggs of Opisthorchis viverrini are visually indisgushiable in Kato technique
smears from other eggs of flukes from other fluke family Heterophyidae
.
The metacercariae of Opisthorchis viverrini are brownish, eliptical with two nearly equal-sized suckers: the oral sucker and the ventral sucker. They are 0.19-0.25 × 0.15-0.22 mm in size.
. It involves a freshwater snail, in which asexual reproduction takes place, and freshwater cyprinid fishes (family Cyprinidae) as intermediate hosts. Fish–eating (= piscivorous) mammals, including humans, dogs and cats, act as definitive hosts, in which sexual reproduction occurs. As a result of poor sanitation
practices and inadequate sewerage
infrastructure, Opisthorchis viverrini-infected people pass the trematode's eggs in their feces into bodies of fresh water.
s include freshwater snails of the genus Bithynia. The only known host is Bithynia siamensis
(that include all its three subspecies). Aquatic snails, which represent the first intermediate hosts of Opisthorchis viverrini, ingest the eggs from which the miracidia undergo asexual reproduction before a population of the free swimming larval stage, called a cercaria, is shed from the infected snails.
In 1965 there were known 9 fish hosts of Opisthorchis viverrini. Up to 2002 there were known 15 species of fishes from 7 genera of the family Cyprinidae, that serves as second intermediate host. Further research by Rim et al. (2008) showed additional five more host species:
(Prionailurus bengalensis). The young adult worm escapes from the metacercarial cyst in the upper small intestine and then migrates through the ampulla of Vater into the biliary tree, where it develops to sexual maturity over four to six weeks, thus completing the life cycle.
Fish contain more metacercaria from September to February, before the dry season and this is the period, when humans are usually infected. Infection
is acquired when people ingest raw or undercooked fish. Dishes of raw fish are common in the cuisine of Laos
and the cuisine of Thailand
: koi-pla, raw fish in spicy salad lab-pla, salted semi-fermented
fish dishes called pla-ra (pla ra
), pla som and Som fak.
The adult worms, which are hermaphrodites, can live for many years in the liver
, even decades, shedding as many as 200 eggs per day which pass out via bile into the chyme
and feces. The lifespan of Opisthorchis viverrini is over 10 years.
Opisthorchis viverrini secretes a granulin
-like growth protein especially in its gut and integument.
s caused by Opisthorchis viverrini in Laos and in Thailand costs about $120 million annually or $120 million per year can cost Northeast Thailand only.
Infection of Opisthorchis viverrini and of other liver flukes in Asia affect the poor and poorest people
. Opisthorchiasis have received less attention in comparison of other diseases and it is a neglected disease in Asia.
s (ESTs) are publicly available for Opisthorchis viverrini, a dataset far too small to give sufficient insights into transcriptome
s for the purpose of supporting genomic and other fundamental molecular research.
Although the genome size of Opisthorchis viverrini has not yet been reported, it is known to have six pairs of chromosome
s, i.e. 2n = 12.
Liver fluke
Liver flukes are a polyphyletic group of trematodes .Adults of liver flukes are localized in the liver of various mammals, including humans. These flatworms can occur in bile ducts, gallbladder, and liver parenchyma. They feed on blood...
, is a trematode
Trematoda
Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic flatworms, commonly referred to as "flukes".-Taxonomy and biodiversity:...
parasite from the family Opisthorchiidae
Opisthorchiidae
Opisthorchiidae is a family of digeneans, parasitic flatworms.The most medically important species in the family Opisthorchiidae are Clonorchis sinensis, Opisthorchis viverrini and Opisthorchis felineus, that are causing disease clonorchiasis....
that attacks the area of the bile duct
Bile duct
A bile duct is any of a number of long tube-like structures that carry bile.Bile, required for the digestion of food, is excreted by the liver into passages that carry bile toward the hepatic duct, which joins with the cystic duct to form the common bile duct, which opens into the intestine.The...
. Infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
is acquired when people ingest raw or undercooked fish. It causes the disease opisthorchiasis
Opisthorchiasis
Opisthorchiasis is an parasitic disease caused by species in the genus Opisthorchis ....
(also called clonorchiasis). Opisthorchis viverrini infection also predisposes the infected for cholangiocarcinoma
Cholangiocarcinoma
Cholangiocarcinoma is a cancer of the bile ducts which drain bile from the liver into the small intestine. Other biliary tract cancers include pancreatic cancer, gallbladder cancer, and cancer of the ampulla of Vater...
, a cancer of the gall bladder and/or its ducts.
Opisthorchis viverrini (together with Clonorchis sinensis
Clonorchis sinensis
Clonorchis sinensis, the Chinese liver fluke, is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile...
and Opisthorchis felineus
Opisthorchis felineus
Opisthorchis felineus, or cat liver fluke is a trematode parasite that infects the liver in mammals. It was first discovered in 1884 in a cat's liver by Sebastiano Rivolta of Italy. In 1891, Russian scientist K.N. Vinogradov found it in a human, and named the parasite a "Siberian liver fluke"...
) is one of the three most medically important species in the family Opisthorchiidae.
Opisthorchis viverrini is endemic throughout Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
, the Lao People's Democratic Republic, Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
and Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
. In Northern Thailand, it is widely distributed, with high prevalence in humans, while in Central Thailand there is low rate of prevalence. The disease opisthorchiasis (caused by Opisthorchis viverrini) does not occur in southern Thailand.
Description
The testes of an adult Opisthorchis viverrini are lobed in comparison of dendritic testes of Clonorchis sinensisClonorchis sinensis
Clonorchis sinensis, the Chinese liver fluke, is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile...
.
The eggs of Opisthorchis viverrini are 30 × 12 μm in size and they are slightly narrower and more regularly ovoid than in Clonorchis sinensis. But eggs of Opisthorchis viverrini are visually indisgushiable in Kato technique
Kato technique
The Kato technique is a laboratory method for preparing human stool samples prior to searching for parasite eggs.- Indications :...
smears from other eggs of flukes from other fluke family Heterophyidae
Heterophyidae
Heterophyidae is a family of intestinal flukes of the class trematoda.Tegument covered by spines. Oral sucker not armed or armed by cyrcumoral spines. Pharynx presented. Genital synus presented. Ventral and genital suckers ussualy not combined. Cirrus and bursa absent. Two testes located in...
.
The metacercariae of Opisthorchis viverrini are brownish, eliptical with two nearly equal-sized suckers: the oral sucker and the ventral sucker. They are 0.19-0.25 × 0.15-0.22 mm in size.
Life cycle
Opisthorchis viverrini is a hermaphroditic liver fluke. Its life cycle is similar to the life cycle of Clonorchis sinensisClonorchis sinensis
Clonorchis sinensis, the Chinese liver fluke, is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile...
. It involves a freshwater snail, in which asexual reproduction takes place, and freshwater cyprinid fishes (family Cyprinidae) as intermediate hosts. Fish–eating (= piscivorous) mammals, including humans, dogs and cats, act as definitive hosts, in which sexual reproduction occurs. As a result of poor sanitation
Sanitation
Sanitation is the hygienic means of promoting health through prevention of human contact with the hazards of wastes. Hazards can be either physical, microbiological, biological or chemical agents of disease. Wastes that can cause health problems are human and animal feces, solid wastes, domestic...
practices and inadequate sewerage
Sewerage
Sewerage refers to the infrastructure that conveys sewage. It encompasses receiving drains, manholes, pumping stations, storm overflows, screening chambers, etc. of the sanitary sewer...
infrastructure, Opisthorchis viverrini-infected people pass the trematode's eggs in their feces into bodies of fresh water.
First intermediate host
The first intermediate hostIntermediate host
A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which some developmental stage is completed. For trypanosomes, the cause of sleeping sickness, humans are the primary host, while the tsetse fly is the secondary host...
s include freshwater snails of the genus Bithynia. The only known host is Bithynia siamensis
Bithynia siamensis
Bithynia siamensis is a species of a freshwater snail with a gill and an operculum, an aquatic prosobranch gastropod mollusk in the family Bithyniidae.- Subspecies :* Bithynia siamensis siamensis - synonym: Bithynia siamensis goniomphalus...
(that include all its three subspecies). Aquatic snails, which represent the first intermediate hosts of Opisthorchis viverrini, ingest the eggs from which the miracidia undergo asexual reproduction before a population of the free swimming larval stage, called a cercaria, is shed from the infected snails.
Second intermediate host
The cercaria then locates a cyprinoid fish, encysts in the fins, skin and musculature of the fish, and becomes a metacercaria. Habitats of second intermediate hosts of Opisthorchis viverrini include freshwater habitats with stagnant or slow-moving waters (ponds, river, aquaculture, swamps, rice fields).In 1965 there were known 9 fish hosts of Opisthorchis viverrini. Up to 2002 there were known 15 species of fishes from 7 genera of the family Cyprinidae, that serves as second intermediate host. Further research by Rim et al. (2008) showed additional five more host species:
- Puntius brevisPuntius brevisPuntius brevis is a species of ray-finned fish in the genus Puntius. It is found in Mekong and Chao Phraya Basins....
- Puntius gonionotus - synonym: Barbonymus gonionotus, Java BarbJava BarbThe Java Barb, more commonly known as Silver Barb in aquaculture, , Pla taphian; Lao Pa keng; , is a species of ray-finned fish in the genus Barbonymus.-Aquaculture:...
- Puntius orphoidesPuntius orphoidesPuntius orphoides is a species of ray-finned fish in the genus Puntius. It is found in Malay Peninsula and Indonesia....
- Puntius proctozysron - synonym: Puntioplites proctozystronPuntioplites proctozystronPuntioplites proctozystron is a species of ray-finned fish in the genus Puntioplites....
- Puntius viehoeveri - synonym: Barbonymus gonionotus
- Hampala dispar
- Hampala macrolepidota
- Cyclocheilichthys armatusCyclocheilichthys armatusCyclocheilichthys armatus is a species of ray-finned fish in the genus Cyclocheilichthys....
- synonym: Cyclocheilichthys siaja - Cyclocheilichthys repassonCyclocheilichthys repassonCyclocheilichthys repasson is a species of ray-finned fish in the genus Cyclocheilichthys....
- Labiobarbus lineatus
- Esomus metallicus
- Mystacoleucus marginatus
- Puntioplites falciferPuntioplites falciferPuntioplites falcifer is a species of ray-finned fish in the genus Puntioplites....
- Onychostoma elongatum
- Osteochilus hasseltii
- Hypsibarbus lagleriHypsibarbus lagleriHypsibarbus lagleri is a species of ray-finned fish in the genus Hypsibarbus....
- Barbodes gonionotus - synonym: Barbonymus gonionotus
Definitive host
The metacercarial stage is infective to humans and other fish-eating mammals including dogs and cats. The natural definitive host is the Leopard CatLeopard Cat
The leopard cat is a small wild cat of South and East Asia. Since 2002 it has been listed as Least Concern by IUCN as it is widely distributed but threatened by habitat loss and hunting in parts of its range...
(Prionailurus bengalensis). The young adult worm escapes from the metacercarial cyst in the upper small intestine and then migrates through the ampulla of Vater into the biliary tree, where it develops to sexual maturity over four to six weeks, thus completing the life cycle.
Fish contain more metacercaria from September to February, before the dry season and this is the period, when humans are usually infected. Infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
is acquired when people ingest raw or undercooked fish. Dishes of raw fish are common in the cuisine of Laos
Cuisine of Laos
Lao cuisine is the cuisine of Laos, which is distinct from other Southeast Asian cuisines. Laos shares borders with neighboring countries and as a result, Lao cuisine has strongly influenced the neighboring cuisine of Northeastern Thailand and some Lao culinary influences have also reached...
and the cuisine of Thailand
Cuisine of Thailand
Thai cuisine is the national cuisine of Thailand. Blending elements of several Southeast Asian traditions, Thai cooking places emphasis on lightly prepared dishes with strong aromatic components. The spiciness of Thai cuisine is well known. As with other Asian cuisines, balance, detail and variety...
: koi-pla, raw fish in spicy salad lab-pla, salted semi-fermented
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...
fish dishes called pla-ra (pla ra
Pla ra
Pla ra is fermented fish sauce, popular in Northeastern Thai cuisine.It is made by pickling several varieties of fish, mainly Snakehead Murrel . The fish is cleaned and cut into pieces, after which it is mixed with salt and rice bran...
), pla som and Som fak.
The adult worms, which are hermaphrodites, can live for many years in the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, even decades, shedding as many as 200 eggs per day which pass out via bile into the chyme
Chyme
Chyme is the semifluid mass of partly digested food expelled by the stomach into the duodenum.Also known as chymus, it is the liquid substance found in the stomach before passing through the pyloric valve and entering the duodenum...
and feces. The lifespan of Opisthorchis viverrini is over 10 years.
Opisthorchis viverrini secretes a granulin
Granulin
Granulin is a protein that in humans is encoded by the GRN gene.- Structure :Granulins are a family of secreted, glycosylated peptides that are cleaved from a single precursor protein with 7.5 repeats of a highly conserved 12-cysteine granulin/epithelin motif. The 88 kDa precursor protein,...
-like growth protein especially in its gut and integument.
Effect on human health
Medical care and loss of wageWage
A wage is a compensation, usually financial, received by workers in exchange for their labor.Compensation in terms of wages is given to workers and compensation in terms of salary is given to employees...
s caused by Opisthorchis viverrini in Laos and in Thailand costs about $120 million annually or $120 million per year can cost Northeast Thailand only.
Infection of Opisthorchis viverrini and of other liver flukes in Asia affect the poor and poorest people
Poverty
Poverty is the lack of a certain amount of material possessions or money. Absolute poverty or destitution is inability to afford basic human needs, which commonly includes clean and fresh water, nutrition, health care, education, clothing and shelter. About 1.7 billion people are estimated to live...
. Opisthorchiasis have received less attention in comparison of other diseases and it is a neglected disease in Asia.
Genetics
Currently, a total of only ~5,000 expressed sequence tagExpressed sequence tag
An expressed sequence tag or EST is a short sub-sequence of a cDNA sequence. They may be used to identify gene transcripts, and are instrumental in gene discovery and gene sequence determination. The identification of ESTs has proceeded rapidly, with approximately 65.9 million ESTs now available in...
s (ESTs) are publicly available for Opisthorchis viverrini, a dataset far too small to give sufficient insights into transcriptome
Transcriptome
The transcriptome is the set of all RNA molecules, including mRNA, rRNA, tRNA, and other non-coding RNA produced in one or a population of cells.-Scope:...
s for the purpose of supporting genomic and other fundamental molecular research.
Although the genome size of Opisthorchis viverrini has not yet been reported, it is known to have six pairs of chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s, i.e. 2n = 12.
External links
- Upatham E.S. & Viyanant V. (2003). "Opisthorchis viverrini and opisthorchiasis: a historical review and future perspective". Acta Tropica 88(3): 171–176. doi:10.1016/j.actatropica.2003.01.001.
- Andrews R. H., Sithithaworn P. & Petney T. N. (2008). "Opisthorchis viverrini: an underestimated parasite in world health". Trends Parasitol. 24(11): 497–501. doi:10.1016/j.pt.2008.08.011,
- Kaewpitoon N., Kaewpitoon S. J., Pengsaa P. & Sripa B. (2008). "Opisthorchis viverrini: The carcinogenic human liver fluke". World Journal of Gastroenterology 14(5): 666-674. doi:10.3748/wjg.14.666. HTM .
- Kaewkes S. (2003). "Taxonomy and biology of liver flukes". Acta Tropica 88(3): 177-186. doi:10.1016/j.actatropica.2003.05.001,
- Adam R., Arnold H., Hinz E. & Storch V. (1995). "Morphology and ultrastructure of the redia and pre-emergent cercaria of Opisthorchis viverrini (Trematoda: Digenea) in the intermediate host Bithynia siamensis goniomphalus (Prosobranchia: Bithyniidae)". Applied parasitology 36(2): 136-154.
- Inatomi S., Tongu Y., Sakumoto D., Suguri S. & Itano K. (1971). "The ultrastructure of helminth. VI. The body wall of Opisthorchis viverrini (Poirier, 1886)". Acta medica Okayama 25(2): 129-142. .