Metorchis conjunctus
Species of fluke From Wikipedia, the free encyclopedia
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.
| Metorchis conjunctus | |
|---|---|
| |
| Drawing of ventral view of Metorchis conjunctus, scale bar is 1 mm | |
| Scientific classification | |
| 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] | |
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 1⁄4–3⁄8 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]
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
Summarize
Perspective
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]
References
External links
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