Metorchis conjunctus | |
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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
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Binomial name | |
Metorchis conjunctus
Cobbold, 1860
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Synonyms [3] | |
Parametorchis noveboracensis (Hung, 1926)
[1] |
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.
This species was discovered and described by Thomas Spencer Cobbold in 1860.
The distribution of M. conjunctus includes:
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. [2] No prepharynx is present. [2] The pharynx is strongly muscular. [2] The esophagus is very short. [2] The intestinal ceca vary from almost straight to sinuous. [2] The acetabulum is slightly oval and weakly muscular. [2] The male has an anterior testis and a posterior testis. [2] The testes vary from almost round to oval, and may be deeply lobed or slightly indented. [2] No cirrus pouch is found. [2] The seminal vesicle is slender. [2] The ovary is trilobed. [2] The receptaculum seminis is elongated or pyriform, and slightly twisted, and situated to the right and behind the ovary. [2]
The eggs are oval and yellowish brown. [2]
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), [3] 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]
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]
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]
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]
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. [3]
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]
This article incorporates public domain text from the reference [2]