''Clonorchis sinensis'', the Chinese liver fluke, is a
liver fluke
Liver fluke is a collective name of a polyphyletic group of parasitic trematodes under the phylum Platyhelminthes.
They are principally parasites of the liver of various mammals, including humans. Capable of moving along the blood circulation, t ...
belonging to the class
Trematoda
Trematoda is a Class (biology), class of flatworms known as flukes. They are obligate parasite, obligate internal Parasitism, parasites with a complex biological life cycle, life cycle requiring at least two Host_(biology), hosts. The intermedia ...
, phylum
Platyhelminthes
The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek language, Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a Phylum (biology), phylum of relati ...
. It infects fish-eating mammals, including humans. In humans, it infects the common
bile duct
A bile duct is any of a number of long tube-like structures that carry bile, and is present in most vertebrates.
Bile is required for the digestion of food and is secreted by the liver into passages that carry bile toward the hepatic duct. It ...
and
gall bladder
In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, although ...
, feeding on
bile
Bile (from Latin ''bilis''), or gall, is a dark-green-to-yellowish-brown fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is produced continuously by the liver (liver bile ...
. It was discovered by British physician James McConnell at the Medical College Hospital in Calcutta (Kolkata) in 1874. The first description was given by
Thomas Spencer Cobbold
Thomas Spencer Cobbold FRS (26 May 182810 March 1886) was an English biologist.
Life
He was born at Ipswich, the third son of Rev. Richard Cobbold, author of the ''History of Margaret Catchpole''.
After graduating in medicine at the Univers ...
, who named it ''Distoma sinense''. The fluke passes its lifecycle in three different hosts, namely freshwater snail as first intermediate hosts, freshwater fish as second intermediate host, and mammals as definitive hosts.
Endemic to Asia and Russia, ''C. sinensis'' is the most prevalent human fluke in Asia and third-most in the world. It is still actively transmitted in
Korea
Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...
, China,
Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
, and
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
. Most infections (about 85%) occur in China.
The infection, called
clonorchiasis
Clonorchiasis is an infectious disease caused by the Chinese liver fluke (''Clonorchis sinensis'') and two related species.
Clonorchiasis is a known risk factor for the development of cholangiocarcinoma, a neoplasm of the biliary system.
Sympt ...
, generally appears as jaundice, indigestion, biliary inflammation, bile duct obstruction, and even
liver cirrhosis
Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. Damage causes tissue repai ...
,
cholangiocarcinoma
Cholangiocarcinoma, also known as bile duct cancer, is a type of cancer that forms in the bile ducts. Symptoms of cholangiocarcinoma may include abdominal pain, yellowish skin, weight loss, generalized itching, and fever. Light colored stool ...
, and
hepatic carcinoma.
As a major causative agent of bile duct cancer, the
International Agency for Research on Cancer
The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations.
Its role is to conduct and ...
has classified ''C. sinensis'' as a group 1 biological
carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...
in 2009.
Discovery
The symptoms of ''C. sinensis'' infection (clonorchiasis) have been known from ancient times in China. The earliest record is from corpses buried in 278 BC at Jiangling County of Hubei Province and the Warring States tomb of the western
Han Dynasty
The Han dynasty (, ; ) was an imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–207 BC) and a warr ...
. The parasite was discovered only in 1874, though, by James McConnell, a professor of pathology and resident physician at the Medical College Hospital in Calcutta. He recovered the fluke from a 20-year-old Chinese carpenter who died on 8 September 1874. On autopsy, he observed that the corpse had a swollen liver (
hepatomegaly
Hepatomegaly is the condition of having an enlarged liver. It is a non-specific medical sign having many causes, which can broadly be broken down into infection, hepatic tumours, or metabolic disorder. Often, hepatomegaly will present as an abdomi ...
) and distended bile ducts, which he noted were blocked by "small, dark, vermicular-looking bodies." He recovered the ''vermicules'' (worms) and compared them with known flukes ''
Fasciola hepatica
''Fasciola hepatica'', also known as the common liver fluke or sheep liver fluke, is a parasitic trematode (fluke or flatworm, a type of helminth) of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, inc ...
'' and ''Distoma lanceolatum''. He concluded that the new fluke was significantly different. He published his observations in the 21 August 1875 issue of ''
The Lancet
''The Lancet'' is a weekly peer-reviewed general medical journal and one of the oldest of its kind. It is also the world's highest-impact academic journal. It was founded in England in 1823.
The journal publishes original research articles, ...
''.
The formal scientific description was published in 1875 by
Thomas Spencer Cobbold
Thomas Spencer Cobbold FRS (26 May 182810 March 1886) was an English biologist.
Life
He was born at Ipswich, the third son of Rev. Richard Cobbold, author of the ''History of Margaret Catchpole''.
After graduating in medicine at the Univers ...
, who named it ''Distoma sinense''. In 1876,
Rudolf Leuckart
Karl Georg Friedrich Rudolf Leuckart (7 October 1822 – 22 February 1898) was a German zoologist born in Helmstedt. He was a nephew to naturalist Friedrich Sigismund Leuckart (1794–1843).
Academic career
He earned his degree from the Uni ...
named it ''Distomum spithulatum''. Kenso Ishisaka recorded the first case of clonorchiasis in Japan in 1877. McConnell identified another infection in a Chinese cook from Hong Kong in 1878. Erwin von Baelz reported the presence of similar flukes from an autopsy of a Japanese patient at Tokyo University in 1883. He recorded two different forms, naming the smaller, more pathogenic form as ''Distoma hepatis endemicum sive perniciosum'', and the larger, less pathogenic form as ''D.h.e.s. innocuum''.
Isao Ijima
was a Japanese zoologist known for his studies of sponges (Porifera) — including his circumscription of the genus '' Staurocalyptus'' — leeches (Hirudinea), flatworms (Turbellaria), birds, and fish. Professor of Zoology at Tokyo Imperial U ...
correctly redescribed them as the same species, but still wrongly renamed it ''Distoma endemicum'' in 1886. When a new genus ''
Opisthorchis
''Opisthorchis'' is a genus of flukes in the family Opisthorchiidae.
Species
Species in the genus ''Opisthorchis'' include:
* '' Opisthorchis chabaudi'' Bourgat & Kulo, 1977
* '' Opisthorchis felineus'' (Rivolta, 1884)
* '' Opisthorchis gomt ...
'' was created by
Émile Blanchard
Charles Émile Blanchard (6 March 1819 – 11 February 1900) was a French zoologist and entomologist.
Career
Blanchard was born in Paris. His father was an artist and naturalist and Émile began natural history very early in life. When he wa ...
in 1895, Cobbold's species name ''D. sinense'' was moved to the new genus because of close similarities with the other members. Further analyses by
Arthur Looss
Arthur Looss (16 March 1861 – 4 May 1923) was a German zoologist and parasitologist. Looss was born in 1861 in Chemnitz, and was educated both there and in Łódź, Poland. Thereafter, he studied at the University of Leipzig, where he received ...
, though, showed significant differences from the general features of ''Opisthorchis'', particularly on the highly branched testes. He created a new genus ''Clonorchis'' (from Greek ''klon'' meaning "twig/branch", ''orkhis'' meaning "testis") in 1907. Similar to Baelz, he differentiated the larger species as ''Clonorchis sinensis'', which is mostly found in China, and the smaller species as ''C. endemicum'', found mostly in Japan. In 1912, Harujiro Kobayashi corrected the classification that the differences in sizes were due to the nature of the host and intensity of infection, and had nothing to do with the biology.
Hence, he supported only ''C. sinensis''. Kobayashi was also the first to discover fish as the second intermediate host in 1911. Masatomo Muto discovered snails as the first intermediate host in 1918.
Description
![Clonorchis](https://upload.wikimedia.org/wikipedia/commons/9/92/Clonorchis.jpg)
An adult ''C. sinensis'' is a flattened (dorsoventrally) and leaf-shaped fluke. The body is slightly elongated and slender, measuring 15–20 mm in length and 3–4 mm in width.
It narrows at the anterior region into a small opening called the
oral sucker, which act as the mouth. From the mouth, two tubes called caeca run the length of body. They are the digestive and excretory tracts. The posterior end is broad and blunt. A poorly developed ventral sucker lies behind the oral sucker, at about one-fourth of the body length from the anterior end. A common genital pore opens just in front of it. As a
hermaphrodite
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 Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...
, it has both male and female reproductive organs. A single rounded ovary is at the centre of the body, and two testes are towards the posterior end. The uterus from the ovary, and seminal ducts from the testes, meet and open at the genital pore. The testes are highly branched. Other highly branched organs called vitellaria (or vitelline glands) are distributed on either side of the body.
The eggs are similar to those of other related flukes such as ''
Opisthorchis viverrini
''Opisthorchis viverrini'', common name Southeast Asian liver fluke, is a food-borne trematode parasite from the family Opisthorchiidae that infects the bile duct. People are infected after eating raw or undercooked fish. Infection with the par ...
'' and ''
O. felineus'', and are often confused during diagnosis. They small and oval in shape, measuring about 30 x 15 μm in diameter. They are sharply curved and with a clear convex operculum towards the narrower end. At the broader end is a stem-shaped knob. The miracidium can be seen inside the fertilised egg.
''Lifecycle''
Production of eggs
The eggs of a ''C. sinensis'' are released through the biliary tract, and excreted out along with the faeces. The eggs are embryonated and contain the larvae called
miracidia
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 ...
. Unlike most other flukes in which the miracidia undergo development and swim in water to infect suitable host, the eggs of ''C. sinensis'' are simply deposited in water. The eggs are then eaten by snails.
First intermediate 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 ...
''
Parafossarulus manchouricus'' often serves as a first
intermediate host
In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...
for ''C. sinensis'' in China, Japan, Korea, and Russia.
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
(1995). ''Control of Foodborne Trematode Infection''. WHO Technical Report Series. 849
PDF part 1
PDF part 2
page 125-126. Other snail hosts include ''
Alocinma longicornis'' ''
Bithynia longicornis'', ''
Bithynia fuchsiana'', ''
Bithynia misella'', ''
Parafossarulus anomalospiralis'', ''
Melanoides tuberculata
The red-rimmed melania (''Melanoides tuberculata''), also known as Malayan livebearing snails or Malayan/Malaysian trumpet snails (often abbreviated to MTS) by aquarists, is a species of freshwater snail with an operculum, a parthenogenetic, a ...
'', ''
Semisulcospira cancellata'', ''
Koreoleptoxis amurensis'', ''
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 count ...
'', and ''
Assiminea lutea'' in China;
and ''
Melanoides tuberculata
The red-rimmed melania (''Melanoides tuberculata''), also known as Malayan livebearing snails or Malayan/Malaysian trumpet snails (often abbreviated to MTS) by aquarists, is a species of freshwater snail with an operculum, a parthenogenetic, a ...
'' in Vietnam.
Once inside of the snail body, the embryonic membrane is dissolved by the snail's digestive enzymes, so the miracidium hatches from the egg. The ciliated miracidium can move about, penetrating the intestine, and enters the haemocoel and digestive gland. Here, it undergoes
metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...
into a sporocyst. The sporocyst gives rise to small larvae called rediae. The rediae burst out from the sporocyst to become the next-stage larvae called cercaria. This system of asexual reproduction allows for an exponential multiplication of cercaria individuals from one miracidium. This aids the fluke in reproduction, because it enables the miracidium to capitalize on one-chance occasion of passively being eaten by a snail before the egg dies. The mature cercariae bore out of the snail body into the freshwater environment. However, they are nonfeeding and must find a fish host within 2–3 days, otherwise they die.
The cercariae of ''C. sinensis'' are different from those of other flukes in that they do not swim. Instead, they initially hang upside down in the water, and then sink to the bottom. They rise to the water surface to resume their initial position, and the movement is repeated again. They attack fish when they feel any disturbance.
Second intermediate host
When they detect fish, they attach themselves on the scales using their suckers. Boring their way into the fish's body, they penetrate into the fish muscle within 6 to 13 minutes. Within an hour of penetration, they develop hard coverings called cysts and become metacercariae. This protective cyst is useful when the fish muscle is consumed. The metacercariae gradually develop and become infective to their next hosts after 3 to 4 weeks.
The common second intermediate hosts are
freshwater fish
Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 1.05%. These environments differ from marine conditions in many ways, especially the difference in levels of s ...
such as
common carp
The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...
(''Cyprinus carpio''),
grass carp
The grass carp (''Ctenopharyngodon idella'') is a species of large herbivorous freshwater fish in the family Cyprinidae, native to the Pacific Far East, with a native range stretching from northern Vietnam to the Amur River on the Sino-Russian ...
(''Ctenopharyngodon idellus''),
crucian carp
The crucian carp (''Carassius carassius'') is a medium-sized member of the common carp family Cyprinidae. It occurs widely in northern European regions. Its name derives from the Low German ''karusse'' or ''karutze'', possibly from Medieval Lat ...
(''Carassius carassius''),
goldfish
The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the wild have ...
(''Carassius auratus''), ''
Pseudorasbora parva
The stone moroko (''Pseudorasbora parva''), also known as the topmouth gudgeon, is a fish belonging to the Cyprinid family, native to Asia, but introduced and now considered an invasive species in Europe and North America. The fish's size is rare ...
'', ''
Abbottina rivularis
''Abbottina rivularis'' (Chinese false gudgeon or Amur false gudgeon) is a species of ray-finned fish in the family Cyprinidae, the carps and minnows. It is native to China, Korea, and Japan. It has been introduced to the Mekong River Basin ...
'', ''
Hemiculter'' spp., ''
Opsariichthys
''Opsariichthys'' is a genus of cyprinid fish found in freshwater habitats in Mainland China (including Hainan), Taiwan, Japan, Korea, and Vietnam. There are currently 12 described species in the genus.
Species
There are 12 species, some with u ...
'' spp., ''
Rhodeus
''Rhodeus'' is a genus of cyprinid fish, consisting of 23 species called bitterlings. The scientific name is derived from the Greek word ', meaning "rose". Most species in the genus are restricted to Asia, but two species are found in Europe ('' ...
'' spp., ''
Sarcocheilichthys
''Sarcocheilichthys'' is a genus of cyprinid fishes found in eastern Asia. There are currently 12 species in the genus.
Species
* '' Sarcocheilichthys biwaensis'' K. Hosoya, 1982
* '' Sarcocheilichthys caobangensis'' V. H. Nguyễn & V. B. Vo ...
'' spp., ''
Zacco platypus'', ''
Nipponocypris temminckii
''Nipponocypris temminckii'' (common name: the Dark chub) is a species of cyprinid in the genus ''Nipponocypris''. It inhabits China, Japan and Korea
Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has be ...
'', and
pond smelt
The pond smelt (''Hypomesus olidus'') is a freshwater species of smelt that inhabits the Arctic
The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and pa ...
(''Hypomesus olidus'').
In China, 102 species of fish and four species of shrimp are known to be the intermediate hosts.
In Korea, 40 species of freshwater fish are recorded as hosts. Seven species of fish are known as hosts in Russia.
Definitive host
Humans are the major definitive hosts. Infection occurs when raw or undercooked fish contaminated with the metacercariae is eaten. The cysts of the metacercariae are gradually digested by the human gastric acids, and upon reaching the small intestines, the entire cyst is lost. The free metacercariae penetrate the intestinal mucosa and enter the bile ducts. Migration into the bile ducts takes 1–2 days. They start feeding on the bile secreted from the liver, and gradually grow.
They become adults in about a month, and start laying eggs. The average lifespan of an adult fluke is 30 years.
An individual fluke can produce 4,000 eggs in a day.
Other definitive hosts are fish-eating mammals such as
dogs
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
,
cats
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of t ...
,
rats
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' (pack rats), ''Bandicota'' (bandicoot ...
,
pigs
The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus s ...
,
badgers
Badgers are short-legged omnivores in the family Mustelidae (which also includes the otters, wolverines, martens, minks, polecats, weasels, and ferrets). Badgers are a polyphyletic rather than a natural taxonomic grouping, being united by the ...
,
weasels
Weasels are mammals of the genus ''Mustela'' of the family Mustelidae. The genus ''Mustela'' includes the least weasels, polecats, stoats, ferrets and European mink. Members of this genus are small, active predators, with long and slender b ...
,
camels
A camel (from: la, camelus and grc-gre, κάμηλος (''kamēlos'') from Hebrew or Phoenician: גָמָל ''gāmāl''.) is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. ...
, and
buffaloes.
Prevalence
''C. sinensis'' is estimated to be the third-most prevalent worm parasite in the world. It is endemic to
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
,
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
,
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
,
Taiwan
Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...
, Korea, and
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...
, especially
Vietnam
Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...
. In Asia it is the most prevalent human trematode, with over 15 million people estimated to be infected and 200 million people at constant risk of infection.
China has the highest incidence with about 13 million infections, accounting for 85% of the total cases.
[
Infection rates are generally higher in men, fishermen, farmers, businessmen, and catering staff. The infection is more serious in adults aged 40–60 and the elderly. More cases occur in low- or middle-class countries, increasing the disease burden and creating economic problems. Clonorchiasis causes 275,370 disability-adjusted life years (DALY) globally. The calculated economic burden for treating clonorchiasis-related ailments in the Guangdong Province of China alone was $200 million by 2010.]
The type of freshwater fishes and shrimp that are infected by ''C. sinensis'' contributes to the prevalence of infection. Commonly eaten fishes (e.g. ''C. idellus'', ''C. auratus'', ''H. nobilis'', ''C. carpio'', ''H. molitrix'', and ''M. anguillicaudatus'') were found to have the metacercariae when sampled from lakes, rivers, and markets. In total, almost 31 types of freshwater fish and shrimp were found to carry the parasite.
Effects on human health
Dwelling in the bile ducts, ''C. sinensis'' induces an inflammatory reaction, epithelial hyperplasia
Hyperplasia (from ancient Greek ὑπέρ ''huper'' 'over' + πλάσις ''plasis'' 'formation'), or hypergenesis, is an enlargement of an organ or tissue caused by an increase in the amount of organic tissue that results from cell proliferati ...
, and sometimes even cholangiocarcinoma
Cholangiocarcinoma, also known as bile duct cancer, is a type of cancer that forms in the bile ducts. Symptoms of cholangiocarcinoma may include abdominal pain, yellowish skin, weight loss, generalized itching, and fever. Light colored stool ...
, the incidence of which is raised in fluke-infested areas.
One adverse effect of ''Clonorchis'' spp. is the possibility for the adult metacercaria to consume all bile created in the liver, which would inhibit the host human from digesting food, especially fats. Another possibility is obstruction of the bile duct by the parasite or its eggs, leading to biliary obstruction and cholangitis (specifically oriental cholangitis).
Unusual cases of liver abscesses due to clonorchiasis have been reported. Liver abscesses may be seen even without dilatation of intrahepatic bile ducts.
Symptoms
While normally asymptomatic, most pathological manifestations result from inflammation and intermittent obstruction of the biliary ducts. The acute phase consists of abdominal pain with associated nausea and diarrhea. Long-standing infections consist of fatigue, abdominal discomfort, anorexia, weight loss, diarrhea, and jaundice. The pathology of long-standing infections consist of bile stasis, obstruction, bacterial infections, inflammation, periductal fibrosis, and hyperplasia. Development of cholangiocarcinoma is progressive.
Diagnosis and treatment
Infection is detected mainly on identification of eggs by microscopic demonstration in faeces
Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
or in duodenal
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine ...
aspirate, but other sophisticated methods have been developed, such as ELISA
The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
, which has become the most important clinical technique. Diagnosis by detecting DNAs from eggs in faeces are also developed using PCR, real-time PCR, and loop-mediated isothermal amplification
Loop-mediated isothermal amplification (LAMP) is a single-tube technique for the amplification of DNA and a low-cost alternative to detect certain diseases. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) combines LAMP with ...
, which are highly sensitive and specific.
Typical imaging features center around imaging of the liver
The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
with CT, ultrasound
Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
, or MRI
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...
for detection of primary biliary cirrhosis
Primary biliary cholangitis (PBC), previously known as primary biliary cirrhosis, is an autoimmune disease of the liver. It results from a slow, progressive destruction of the small bile ducts of the liver, causing bile and other toxins to build ...
. Traits that raise suspicion for the infection include intra- and extrahepatic dilatation and structures with intraductal pigmented stones, usually in the absence of gallstones and with regions of segmental liver atrophy, particularly the lateral aspect of the left hepatic lobe. Also, reduced arborization of peripheral ducts is seen. A full 5% of chronic infections go on to develop cholangiocarcinoma.
Drugs used to treat infestation include triclabendazole
Triclabendazole, sold under the brand name Egaten among others, is a medication used to treat fascioliasis and paragonimiasis. It is very effective for both conditions. Treatment in hospital may be required. It is taken by mouth with typically ...
, praziquantel
Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of helminthiasis, parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is us ...
, bithionol
Bithionol is an antibacterial, anthelmintic, and algaecide. It is used to treat '' Anoplocephala perfoliata'' (tapeworms) in horses and ''Fasciola hepatica'' (liver flukes).
__TOC__ Mechanism of action
Bithionol has been shown to be a potent in ...
, albendazole
Albendazole (also known as albendazolum) is a broad-spectrum anthelmintic and antiprotozoal agent of the benzimidazole type. It is used for the treatment of a variety of intestinal parasite infections, including ascariasis, pinworm infection, h ...
, levamisole
Levamisole, sold under the brand name Ergamisol among others, is a medication used to treat parasitic worm infections, specifically ascariasis and hookworm infections. It is taken by mouth.
Side effects may include abdominal pain, vomiting, ...
, and mebendazole
Mebendazole (MBZ), sold under the brand name Vermox among others, is a medication used to treat a number of parasitic worm infestations. This includes ascariasis, pinworm infection, hookworm infections, guinea worm infections, hydatid disea ...
. However, benzimidazoles
Benzimidazole is a heterocyclic aromatic organic compound. This bicyclic compound may be viewed as fused rings of the aromatic compounds benzene and imidazole. It is a colorless solid.
Preparation
Benzimidazole is produced by condensation of o ...
are very weak as a vermicide. As with other trematodes, praziquantel is the drug of choice. Lately, tribendimidine
Tribendimidine is a broad-spectrum anthelmintic agent developed in China, at the National Institute of Parasitic Diseases in Shanghai. It is a derivative of amidantel. has been acknowledged as an effective and safe drug.
Genetics
''C. sinensis'' has 28 pairs of chromosomes (2n=56) in a cell. The chromosome pairs are groups in two: 8 large group and 20 small group. Structural variations are seen between those from different countries. The draft genome sequence was published in 2011. The total genome size is estimated to be 580 MB, and the GC content was calculated as about 43.85%. About 16,000 genes are predicted, out of which 13,634 genes have been identified.
See also
* List of parasites (human)
Endoparasites Protozoan organisms
Helminths (worms)
Helminth organisms (also called helminths or intestinal worms) include:
Tapeworms
Flukes
Roundworms
Other organisms
Ectoparasites
References
{{Portal bar, Bio ...
References
Further reading
*
*
External links
* ]
*
*
Discovery of ''Clonorchis Sinensis''
*
*
{{Taxonbar, from=Q1074210
Plagiorchiida
IARC Group 1 carcinogens
Infectious causes of cancer
Parasitic helminths of humans
Animals described in 1907
Foodborne illnesses