Metorchis conjunctus

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Metorchis conjunctus
Metorchis conjunctus 2.png
Drawing of ventral view of Metorchis conjunctus, scale bar is 1 mm
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
Order: Plagiorchiida
Family: Opisthorchiidae
Genus: Metorchis
Species:
M. conjunctus
Binomial name
Metorchis conjunctus
Cobbold, 1860
Synonyms [1]

Parametorchis noveboracensis (Hung, 1926) [2]
Parametorchis intermedius (Price, 1929) [3]
Parametorchis canadensis (Price, 1929) [3]
Parametorchis manitobensis (Allen & Wardle, 1934)

Contents

Metorchis conjunctus, common name Canadian liver fluke, is a species of trematode parasite in the family Opisthorchiidae. It can infect mammals that eat raw fish in North America. The first intermediate host is a freshwater snail and the second is a freshwater fish.

Taxonomy

This species was discovered and described by Thomas Spencer Cobbold in 1860.

Distribution

The distribution of M. conjunctus includes:

Description

The body of M. conjunctus is pear-shaped and flat. [6] The body length is 1438 inch (6.4–9.5 mm). [6] It has a weakly muscular terminal oral sucker. [3] No prepharynx is present. [3] The pharynx is strongly muscular. [3] The esophagus is very short. [3] The intestinal ceca vary from almost straight to sinuous. [3] The acetabulum is slightly oval and weakly muscular. [3] The male has an anterior testis and a posterior testis. [3] The testes vary from almost round to oval, and may be deeply lobed or slightly indented. [3] No cirrus pouch is found. [3] The seminal vesicle is slender. [3] The ovary is trilobed. [3] The receptaculum seminis is elongated or pyriform, and slightly twisted, and situated to the right and behind the ovary. [3]

The eggs are oval and yellowish brown. [3]

Drawing of dorsal view of M. conjunctus, scale bar is 1 mm Metorchis conjunctus 3.png
Drawing of dorsal view of M. conjunctus, scale bar is 1 mm

Lifecycle

The first intermediate host of M. conjunctus is a freshwater snail, Amnicola limosus . [4]

The second intermediate host is a freshwater fish: Catostomus catostomus , [4] Salvelinus fontinalis , [4] Perca flavescens , [4] or Catostomus commersoni . [7] Metacercaria of M. conjunctus were also found in northern pike (Esox lucius). [8]

The definitive hosts are fish-eating mammals such as domestic dogs (Canis lupus familiaris), domestic cats (Felis catus), wolves ( Canis lupus ), [5] red foxes (Vulpes vulpes), [9] gray foxes (Urocyon cinereoargenteus), [1] coyotes (Canis latrans), raccoons ( Procyon lotor ), [5] muskrats (Ondatra zibethicus), American minks (Neovison vision), [5] fishers ( Martes pennanti ), [4] [10] or bears. [8] It can also infect humans. [7] It lives in the bile duct and in the gallbladder. [6]

Effects on human health

M. conjunctus causes a disease called metorchiasis. [11] It has been known to infect humans since 1946. [4] Humans had eggs of M. conjunctus in their stools, but they were asymptomatic. [8] Sashimi from raw Catostomus commersoni was identified as a source for an outbreak in Montreal in 1993. [7] It was the first symptomatic disease in humans caused by M. conjunctus. [8]

Symptoms

After ingestion of fish infected with M. conjunctus, about 1–15 days are needed for symptoms to occur, namely for eggs to be detected in the stool (incubation period). [12]

The acute phase consists of upper abdominal pain and low-grade fever. [7] High concentrations of eosinophil granulocytes are in blood. [7] Also, higher concentrations of liver enzymes are seen. [7] When untreated, symptoms may last from 3 days to 4 weeks. [7] Symptoms of chronic infection were not reported. [12]

Diagnosis and treatment

Eggs of M. conjunctus can be found by stool analysis. [8] Serologic analysis can be also used - ELISA test for IgG antibodies against antigens of M. conjunctus. [8]

Drugs used to treat infestation include praziquantel: [7] 75 mg/kg in three doses per day (the same dosage applies for adults and for children). [8] [13]

Effects on animal health

Watson and Croll (1981) [14] studied symptoms of cats. Prevention includes feeding with cooked fish (not raw fish). [6]

M. conjunctus was found to be a common infection of domestic dogs in First Nations settlements in 1973. [15] It has been in found in other animals including raccoons, minks, and gray foxes. [1]

The prevalence of M. conjunctus in wolves in Canada is 1–3%. [12] In wolves, M. conjunctus causes cholangiohepatitis with periductular fibrosis in the liver. [5] It sometimes causes chronic inflammation and fibrosis of the pancreas in wolves. [5]

Related Research Articles

<span class="mw-page-title-main">Trematoda</span> Class of parasitic flatworms

Trematoda is a class of flatworms known as flukes or trematodes. 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, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five traditional vertebrate classes: mammals, birds, amphibians, reptiles, and fish.

<i>Clonorchis sinensis</i> Species of fluke

Clonorchis sinensis, the Chinese liver fluke, is a liver fluke belonging to the class Trematoda, phylum Platyhelminthes. It infects fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding on 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, 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.

<span class="mw-page-title-main">Clonorchiasis</span> Infectious disease caused by fish parasites

Clonorchiasis is an infectious disease caused by the Chinese liver fluke and two related species. Clonorchiasis is a known risk factor for the development of cholangiocarcinoma, a neoplasm of the biliary system.

<span class="mw-page-title-main">Fasciolosis</span> Parasitic worm infection

Fasciolosis is a parasitic worm infection caused by the common liver fluke Fasciola hepatica as well as by Fasciola gigantica. The disease is a plant-borne trematode zoonosis, and is classified as a neglected tropical disease (NTD). It affects humans, but its main host is ruminants such as cattle and sheep. The disease progresses through four distinct phases; an initial incubation phase of between a few days up to three months with little or no symptoms; an invasive or acute phase which may manifest with: fever, malaise, abdominal pain, gastrointestinal symptoms, urticaria, anemia, jaundice, and respiratory symptoms. The disease later progresses to a latent phase with less symptoms and ultimately into a chronic or obstructive phase months to years later. In the chronic state the disease causes inflammation of the bile ducts, gall bladder and may cause gall stones as well as fibrosis. While chronic inflammation is connected to increased cancer rates, it is unclear whether fasciolosis is associated with increased cancer risk.

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. Metagonimiasis was described by Katsurasa in 1911–1913 when he first observed eggs of M. yokagawai in feces. M. takahashii was described later first by Suzuki in 1930 and then M. miyatai was described in 1984 by Saito.

<i>Fasciola hepatica</i> Species of fluke

Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, including humans, and is transmitted by sheep and cattle to humans all over the world. The disease caused by the fluke is called fasciolosis or fascioliasis, which is a type of helminthiasis and has been classified as a neglected tropical disease. Fasciolosis is currently classified as a plant/food-borne trematode infection, often acquired through eating the parasite's metacercariae encysted on plants. F. hepatica, which is distributed worldwide, has been known as an important parasite of sheep and cattle for decades and causes significant economic losses in these livestock species, up to £23 million in the UK alone. Because of its relatively large size and economic importance, it has been the subject of many scientific investigations and may be the best-known of any trematode species. F. hepatica's closest relative is Fasciola gigantica. These two flukes are sister species; they share many morphological features and can mate with each other.

<i>Fasciola</i> Genus of flukes

Fasciola, commonly known as the liver fluke, is a genus of parasitic trematodes. There are three species within the genus Fasciola: Fasciola nyanzae,Fasciolahepatica and Fasciolagigantica. Fasciola hepatica and F. gigantica are known to form hybrids. Both F. hepatica and F. gigantica and their hybrids infect the liver tissue of a wide variety of mammals, including humans, in a condition known as fascioliasis. F. hepatica measures up to 30 mm by 15 mm, while F. gigantica measures up to 75 mm by 15 mm. Fasciola nyanzae is thought to exclusively infect the common hippopotamus, Hippopotamus amphibius.

<i>Paragonimus westermani</i> Species of fluke

Paragonimus westermani is the most common species of lung fluke that infects humans, causing paragonimiasis. 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 Coenraad Kerbert (1849–1927) in 1878.

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 parasite is called opisthorchiasis. O. viverrini infection also increases the risk of cholangiocarcinoma, a cancer of the bile ducts.

<i>Echinostoma</i> Genus of flukes

Echinostoma is a genus of trematodes (flukes), which can infect both humans and other animals. These intestinal flukes have a three-host life cycle with snails or other aquatic organisms as intermediate hosts, and a variety of animals, including humans, as their definitive hosts.

<span class="mw-page-title-main">Paragonimiasis</span> Medical condition

Paragonimiasis is a food-borne parasitic disease caused by several species of lung flukes belonging to genus Paragonimus. 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.

<i>Dicrocoelium dendriticum</i> Species of fluke

Dicrocoelium dendriticum, the lancet liver fluke, is a parasite fluke that tends to live in cattle or other grazing mammals.

<i>Opisthorchis felineus</i> Species of fluke

Opisthorchis felineus, the Siberian liver fluke 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 parasitologist, Konstantin Nikolaevich Vinogradov (1847–1906) found it in a human, and named the parasite a "Siberian liver fluke". In the 1930s, helminthologist Hans Vogel of Hamburg published an article describing the life cycle of Opisthorchis felineus. Felineus infections may also involve the pancreatic ducts. Diagnosis of Opisthorchis infection is based on microscopic identification of parasite eggs in stool specimens. Safe and effective medication is available to treat Opisthorchis infections. Adequately freezing or cooking fish will kill the parasite.

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<span class="mw-page-title-main">Liver fluke</span> Group of liver parasites

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, they can occur also in bile ducts, gallbladder, and liver parenchyma. In these organs, they produce pathological lesions leading to parasitic diseases. They have complex life cycles requiring two or three different hosts, with free-living larval stages in water.

<i>Heterophyes heterophyes</i> Species of fluke

Heterophyes heterophyes, or the intestinal fish fluke, was discovered by Theodor Maximaillian Bilharz in 1851. This parasite was found during an autopsy of an Egyptian mummy. H. heterophyes is found in the Middle East, West Europe and Africa. They use different species to complete their complex lifestyle. Humans and other mammals are the definitive host, first intermediate host are snails, and second intermediate are fish. Mammals that come in contact with the parasite are dogs, humans, and cats. Snails that are affected by this parasite are the Cerithideopsilla conica. Fish that come in contact with this parasite are Mugil cephalus, Tilapia milotica, Aphanius fasciatus, and Acanthgobius sp. Humans and mammals will come in contact with this parasite by the consumption of contaminated or raw fish. This parasite is one of the smallest endoparasite to infect humans. It can cause intestinal infection called heterophyiasis.

Amphistomiasis is a parasitic disease of livestock animals, more commonly of cattle and sheep, and humans caused by immature helminthic flatworms belonging to the order Echinostomida. The term amphistomiasis is used for broader connotation implying the disease inflicted by members of Echinostomida including the family Paramphistomidae/Gastrodiscidae ; whereas paramphistomiasis is restricted to that of the members of the family Paramphistomidae only. G. discoides and Watsonius watsoni are responsible for the disease in humans, while most paramphistomes are responsible in livestock animals, and some wild mammals. In livestock industry the disease causes heavy economic backlashes due to poor production of milk, meat and wool.

Carcinogenic parasites are parasitic organisms that depend on other organisms for their survival, and cause cancer in such hosts. Three species of flukes (trematodes) are medically-proven carcinogenic parasites, namely the urinary blood fluke, the Southeast Asian liver fluke and the Chinese liver fluke. S. haematobium is prevalent in Africa and the Middle East, and is the leading cause of bladder cancer. O. viverrini and C. sinensis are both found in eastern and southeastern Asia, and are responsible for cholangiocarcinoma. The International Agency for Research on Cancer declared them in 2009 as a Group 1 biological carcinogens in humans.

<span class="mw-page-title-main">Gastropod-borne parasitic disease</span> Medical condition

Gastropod-borne parasitic diseases (GPDs) are a group of infectious diseases that require a gastropod species to serve as an intermediate host for a parasitic organism that can infect humans upon ingesting the parasite or coming into contact with contaminated water sources. These diseases can cause a range of symptoms, from mild discomfort to severe, life-threatening conditions, with them being prevalent in many parts of the world, particularly in developing regions. Preventive measures such as proper sanitation and hygiene practices, avoiding contact with infected gastropods and cooking or boiling food properly can help to reduce the risk of these diseases.

Wolves may suffer from various pathogens, both viral and bacterial, and parasite, both external and internal. Parasitic infection in wolves is of particular concern to people. Wolves can spread them to dogs, which in turn can carry the parasites to humans. In areas where wolves inhabit pastoral areas, the parasites can be spread to livestock.

References

This article incorporates public domain text from the reference [3]

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