Capillaria hepatica
Capillaria hepatica | |
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One of the plates published with the original description of the species, showing the masses of eggs in the liver of the host (above) and free alive eggs (below). | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Nematoda |
Class: | Enoplea |
Order: | Enoplida |
Family: | Capillariidae |
Genus: | Capillaria |
Species: | C. hepatica
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Binomial name | |
Capillaria hepatica Bancroft, 1893
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Capillaria hepatica is a parasitic nematode which causes hepatic capillariasis in rodents and numerous other mammal species, including humans.[1] The life cycle of C. hepatica may be completed in a single host species. However, the eggs, which are laid in the liver, must mature outside of the host body (in the environment) prior to infecting a new host.[1] So the death of the host in which the adults reach sexual maturity, either by being eaten or dying and decomposing, is necessary for completion of the life cycle.
Discovery and taxonomy
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/be/Trichocephalus_hepaticus_Bancroft_1893_-_Plate_VII.jpg/220px-Trichocephalus_hepaticus_Bancroft_1893_-_Plate_VII.jpg)
This species was first described in 1893, from specimens found in the liver of Rattus norvegicus, and named Trichocephalus hepaticus.[2] Various authors have subsequently renamed it Trichosoma hepaticum, Capillaria hepatica, Hepaticola hepatica and Calodium hepaticum.[3][4] Currently it is usually referred to as either Capillaria hepatica or, less often, Calodium hepaticum.[citation needed]
Hosts and distribution
Adults are often found in dozens of rodent species, but also occur in a wide variety of other wild and domestic mammals, and occasionally humans.[5][6] C. hepatica has been found in temperate and tropical zones on every continent and infestation rates of wild-caught rats of up to 100% have been reported.[1][7]
Usually, Capillaria hepatica is found in rodents, monkeys and other animals. Capillaria hepatica is rarely found in humans and at least 40 cases have been reported. There are no endemic areas of infection with C. hepatica and human infection primarily results from
Of the human infections, most have been found in children under the age of 5.[9]
Tissue niche and morphology
The tissue niche of this parasite is the liver. The adult females will deposit eggs in the parenchyma of the liver. Occasionally in humans larvae will migrate to the lungs, kidneys and other organs.[1]
Adult worms take the shape of a slender nematode, with the anterior part of the body narrow and the posterior part gradually swelling.[10] The females measure about 53–78mm x 0.11–0.20mm, but the males are approximately 24–37mm x 0.07–0.10mm.[10] The adult worms are rarely seen intact, as they mature and die in the parenchyma of the liver.[11] The adult females lay eggs that are about 48-66μm x 28-36μm.[10] The shell of the eggs is striated with shallow polar prominences at either end. Numerous mini-pores can be seen in the outer shell as well. Unembryonated eggs may be ingested by a carnivore, in which case they are harmless and pass out in the feces. Eggs will embryonate in the environment, where they require air and damp soil to become infective. Under optimal conditions this takes about 30 days. Larvae are juvenile versions of the adult worm.[1]
Life cycle
Hosts ingest C. hepatica eggs (from sources outlined below) which hatch into first stage larvae (L1). The L1 larvae bore through the intestinal wall and are carried to the liver by the
The eggs in the liver exist in a state of arrested development – they are unable to develop into larvae until they spend some time outside of the host, in the environment. Escaping from the liver tissue may be accomplished either by the death and decomposition of the host's body, or by the consumption and digestion of the host by a
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Calodium_hepaticum_lifecycle.gif/440px-Calodium_hepaticum_lifecycle.gif)
Pathogenesis and survival in host
In humans Capillaria hepatica causes hepatic
This parasite can be fatal in humans, as transmission and survival of the parasite depend on death of the
Diagnosis and treatment
Diagnosis is made by finding eggs or adults of C. hepatica in liver tissue from biopsy or
Successful treatment of human cases with
Two ways of preventing C. hepatica infections in humans are to institute effective rodent control programs and to prevent dogs and cats from eating rodents.[8]
Paleoparasitology
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Parasite130094-fig3_Cysts.tif/lossy-page1-220px-Parasite130094-fig3_Cysts.tif.jpg)
The first
Research uses
The selective liver damage by C. hepatica in rodents has been used in model systems to study the extensive regeneration capabilities of the mammalian liver,[21] and for testing antifibrotic drugs.[22]
C. hepatica has attracted interest for use in
References
- ^ a b c d e f g h i j k l m "Parasites and Health: Capillariasis". Center for Disease Control. Retrieved September 14, 2011.
- S2CID 259695802.
- .
- PMID 7106653.
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- PMID 17998580.
- PMID 16438200.
- ^ a b c d Roberts LS (2009). Foundations of Parasitology. McGraw Hill Higher Education.
- ^ S2CID 39515343.
- ^ PMID 20135717.
- PMID 15891145.
- S2CID 23226752.
- ISBN 978-0-486-65126-2.
- ^ PMID 8107607.
- PMID 17570971.
- PMID 17293985.
- PMID 18487945. Archived from the original(PDF) on July 28, 2011.
- ISBN 978-0-7020-3398-8.
- PMID 15891145.
- PMID 24572211.
- PMID 17992401.
- PMID 11050664.
- ^
- • Saunders G, Cooke B, McColl K, Shine R, Peacock T (2010). "Modern approaches for the biological control of vertebrate pests: An Australian perspective". S2CID 21403820.
- • Saunders G, Cooke B, McColl K, Shine R, Peacock T (2010). "Modern approaches for the biological control of vertebrate pests: An Australian perspective".
- ^
- • SINGLETON GR, BROWN PR, PECH RP, JACOB J, MUTZE GJ, KREBS CJ (2005). "One hundred years of eruptions of house mice in Australia - a natural biological curio". S2CID 12545760.
- • SINGLETON GR, BROWN PR, PECH RP, JACOB J, MUTZE GJ, KREBS CJ (2005). "One hundred years of eruptions of house mice in Australia - a natural biological curio".
Further reading
- [1]
- DOI.org Indian Journal of Pediatrics, publisher Dr. K C Chaudhuri Foundation, co-published by Springer India
- Camargo L. M. A., et al. (2010). "Capillariaisis (Trichurida, Trichinellidae, Capillaria hepatica) in the Brazilian Amazon: low pathogenicity, low infectivity and a novel mode of transmission". PMID 20187941.