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
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 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]

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]

References

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

  1. 1 2 3 Mills J. H. & Hirth R. S. (1968). "Lesions Caused by the Hepatic Trematode, Metorchis conjunctus, Cobbold, 1860: A Comparative Study in Carnivora". Journal of Small Animal Practice 9(1): 1–6. doi : 10.1111/j.1748-5827.1968.tb04678.x.
  2. ↑ Hung See-Lü (1926). "A new species of fluke, Parametorchis noveboracensis, from the cat in the United States". Proceedings of the United States National Museum 69(2627): 1 –2.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Price E. W. (1929). "Two new species of trematodes of the genus Parametorchis from fur-bearing animals". Proceedings of the United States National Museum 76(2809): 1 –5.
  4. 1 2 3 4 5 6 7 8 9 Chai J. Y., Darwin Murrell K. & Lymbery A. J. (2005). "Fish-borne parasitic zoonoses: Status and issues". International Journal for Parasitology 35(11–12): 1233–1254. doi : 10.1016/j.ijpara.2005.07.013.
  5. 1 2 3 4 5 6 7 8 Wobeser G., Runge W. & Stewart R. R. (1983). "Metorchis conjunctus (Cobbold, 1860) infection in wolves (Canis lupus), with pancreatic involvement in two animals". Journal of Wildlife Diseases 19(4): 353–356. PMID   6644936.
  6. 1 2 3 4 Axelson R. D. (1962). "Metorchis Conjunctus Liver Fluke Infestation in a Cat". Canadian Veterinary Journal 3(11): 359–360. PMID   17421548. PDF.
  7. 1 2 3 4 5 6 7 8 MacLean J. D., Arthur J. R., Ward B. J., Gyorkos T. W., Curtis M. A. & Kokoskin E. (1996). "Common-source outbreak of acute infection due to the North American liver fluke Metorchis conjunctus". The Lancet 347(8995): 154–158. doi : 10.1016/S0140-6736(96)90342-6
  8. 1 2 3 4 5 6 7 Behr M. A., Gyorkos T. W., Kokoskin E., Ward B. J., MacLean J. D. (1998). "North American liver fluke (Metorchis conjunctus) in a Canadian aboriginal population: a submerging human pathogen?" Canadian Journal of Public Health 89: 258–259. PMID   9735521. PDF.
  9. ↑ Smith H. J. (1978). "Parasites of red foxes in New Brunswick and Nova Scotia". Journal of Wildlife Diseases 14(3): 366–370. PMID   691132.
  10. ↑ Dick T. A & Leonard R. D. (1979). "Helminth parasites of fisher Martes pennanti (Erxleben) from Manitoba, Canada". Journal of Wildlife Diseases 15(3): 409–412. PMID   574167.
  11. ↑ Dennis J. Richardson; Peter J. Krause (6 December 2012). North American Parasitic Zoonoses. Springer Science & Business Media. p. 86. ISBN   978-1-4615-1123-6.
  12. 1 2 3 Waikagul J. & Thaekham U. (2014). Approaches to Research on the Systematics of Fish-Borne Trematodes. Academic Press, 130 pp., page 6 –7.
  13. ↑ "FLUKE, hermaphroditic, infection"., 2 pp., accessed 31 December 2015.
  14. ↑ Watson T. G & Croll N. A. (1981). "Clinical changes caused by the liver fluke Metorchis conjunctus in cats". Veterinary Pathology 18(6): 778–785. doi : 10.1177/030098588101800608.
  15. ↑ Unruh D. H., King J. E., Eaton R. D. & Allen J. R. (1973). "Parasites of dogs from Indian settlements in northwestern Canada: a survey with public health implications". Canadian Journal of Comparative Medicine 37(1): 25–32. PMID   4265550.
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