Significations et usages de Fasciola_gigantica

Fasciola gigantica is a parasitic flatworm of the class Trematoda, which causes tropical fascioliasis. It is regarded as one of the most important single platyhelminth infections of ruminants in Asia and Africa. Estimates of infection rates are as high as 80-100% in some countries.

  Distribution

Fasciola gigantica causes outbreaks in tropical areas of southern Asia, Southeast Asia, and Africa.^[1] The geographical distribution of Fasciola gigantica overlaps with Fasciola hepatica in many African and Asian countries and sometimes in the same country, although in such cases the ecological requirement of the flukes and their snail host are distinct.^[1]

Infection is most prevalent in regions with intensive sheep and cattle production.^[1]

In Egypt Fasciola gigantica exist in domestic animals since the times of the pharaohs.^[1]

  Life cycle

The life cycle of Fasciola gigantica is as follows: eggs (transported with feces) → eggs hatchs → miracidium → miracidium infect snail intermediate host → (parthenogenesis in 24 hours) sporocyst → redia → daughter redia → cercaria → (gets outside the snail) → metacercaria → infection of the host → adult stage produces eggs.

  Intermediate hosts

As with other trematodes, Fasciola develop in a molluscan intermediate host. Species of the freshwater snails from the family Lymnaeidae are well known for their role as intermediate hosts in the life cycle of Fasciola gigantica; however, throughout the years an increasing number of other molluscan intermediate hosts of Fasciola gigantica have been reported.^[1]

There are many ecological factors affecting snail populations including temperature, light, hydrogen ion concentration (pH), vegetation, depth of water, current of the water, chemical composition of the soil, and snail population competition.^[1] It has been reported that the Lymnaeid intermediate hosts of Fasciola gigantica are distinguishable from those of Fasciola hepatica, both morphologically and as to habitat requirement.^[1] The species of Fasciola can become adapted to new intermediate hosts under certain conditions at least based on laboratory trials.^[1] It has been reported that the most important intermediate host for Fasciola gigantica is Radix auricularia.^[1] However, Lymnaea rufescens and Lymnaea acuminata are the host snails in the Indian Subcontinent; Radix rubiginosa and Radix natalensis are the hosts in Malaysia and in Africa respectively; and the synonymous Lymnaea cailliaudi is the intermediate host in east Africa.^[1]

There is some evidence, at least based on laboratory trails, that the species of Fasciola can become adapted to new hosts, either amphibious or aquatic, under certain conditions.^[1] The Australian Lymnaea tomentosa (host of Fasciola hepatica) was shown to be receptive to miracidia of Fasciola gigantica from East Africa, Malaysa and Indonesia.^[1]

Radix natalensis is considered to be the essential intermediate host for Fasciola gigantica based on field and experimental studies in Egypt.^[1] Cercarial production from Radix natalensis experimentally infected with Fasciola gigantica is affected by the species of definitive host from which the eggs are obtained, as well as the different laboratory conditions.^[1] Another lymnaeid, Galba truncatula, may play a role in transmitting this parasite in Egypt, as it was found naturally infected with Fasciola gigantica.^[1] At the level of intermediate hosts of Fasciola gigantica, the conditions are thus favorable in Egypt to transmit fascioliasis.^[1]

Other species in the family Lymnaeidae are serving as naturally or experimentally intermediate hosts of Fasciola gigantica and they include: Austropeplea ollula,^[2] Austropeplea viridis,^[2] Radix peregra,^[2] Radix auricularia,^[2] Radix natalensis,^[2] Radix luteola,^[2] Radix rubiginosa,^[2] Pseudosuccinea columella^[2] and Galba truncatula.^[2]

  Hosts

Fasciola gigantica is a causative agents (together with Fasciola hepatica) of fascioliasis in ruminants and in humans worldwide.^[1]

The parasite infects cattle and buffalo and can also be seen regionally in goats, sheep, and donkeys.

  Infection

Infection with Fasciola spp. occurs when metacercariae are accidentally ingested on raw vegetation.^[1] The metacercariae exist in the small intestine, and move through the intestinal wall and peritoneal cavity to the liver where adults mature in the biliary ducts of the liver.^[1] Eggs are passed through the bile ducts into the intestine where they are then passed in the feces.^[1]

  Identification

Despite the importance to differentiate between the infection by either fasciolid species, due to their distinct epidemiological, pathological and control characteristics, there is, unfortunately, neither a direct coprological (excretion-related) nor an indirect immunological test available for their diagnosis.^[1] The specific differentiation can only be made by either a morphological study of adult flukes or by molecular tools.^[1]

  Toxicology

The chloroform extract of the leaves of Pycnanthus angolensis (Myristicaceae) and the methanol extracts of the leaves and stem of the same plant exhibited considerable anthelmintic activities in vitro against Fasciola gigantica.^[3]

  References

This article incorporates CC-BY-3.0 text from references.^[1][3]

  Further reading

• Le, T. H.; De, N. V.; Agatsuma, T.; Blair, D.; Vercruysse, J.; Dorny, P.; Nguyen, T. G. T.; McManus, D. P. (2006). "Molecular Confirmation that Fasciola gigantica Can Undertake Aberrant Migrations in Human Hosts". Journal of Clinical Microbiology 45 (2): 648–650. DOI:10.1128/JCM.01151-06. PMC 1829072. PMID 17135435. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1829072.  edit And references within,
• Meemon, K.; Grams, R.; Vichasri-Grams, S.; Hofmann, A.; Korge, G. N.; Viyanant, V.; Upatham, E. S.; Habe, S. et al. (2004). "Molecular cloning and analysis of stage and tissue-specific expression of cathepsin B encoding genes from Fasciola gigantica". Molecular and Biochemical Parasitology 136 (1): 1–10. DOI:10.1016/j.molbiopara.2004.02.010. PMID 15138062.  edit
• Spithill T. M., Smooker P. M. & Copeman D. B. (1999). "Fasciola gigantica: epidemiology, control, immunology and molecular biology". In Dalton J. P.. Fasciolosis. Oxin, UK.: CABI Publishing. pp. 465-525.