Fasciola gigantica

Fasciola gigantica
	Cobbold's drawings of dorsal (left) and ventral views of Fasciola gigantica
Scientific classification
Kingdom:	Animalia
Phylum:	Platyhelminthes
Class:	Rhabditophora
Order:	Plagiorchiida
Family:	Fasciolidae
Genus:	Fasciola
Species:	F. gigantica
Binomial name
	Fasciola gigantica; Cobbold, 1855[1]

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. The infection is commonly called fasciolosis.

The prevalence of F. gigantica often overlaps with that of Fasciola hepatica, and the two species are so closely related in terms of genetics, behaviour, and morphological and anatomical structures that distinguishing them is notoriously difficult.[2] Therefore, sophisticated molecular techniques are required to correctly identify and diagnose the infection.[3]

Distribution

Fasciola gigantica causes outbreaks in tropical areas of South Asia, Southeast Asia, and Africa. The geographical distribution of F. gigantica overlaps with F. 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 hosts are distinct. Infection is most prevalent in regions with intensive sheep and cattle production. In Egypt, F. gigantica has existed in domestic animals since the times of the pharaohs.[4]

Lifecycle

The lifecycle of F. gigantica is: Eggs (transported with feces) → egg hatch → 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 spp. 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 lifecycle of F. gigantica; however, throughout the years, an increasing number of other molluscan intermediate hosts of F. gigantica have been reported.[4] The lymnaeid intermediate hosts of F. gigantica are distinguishable from those of F. hepatica, both morphologically and as to habitat requirement. The species of Fasciola can become adapted to new intermediate hosts under certain conditions at least based on laboratory trials. The most important intermediate host for F. gigantica is Radix auricularia. However, other species are also known to harbour the fluke, including Lymnaea rufescens and Lymnaea acuminata in the Indian subcontinent; Radix rubiginosa and Radix natalensis in Malaysia and Africa, respectively; and the synonymous Lymnaea cailliaudi in East Africa. Other snails also serve as natural or experimental intermediates, such as Austropeplea ollula, Austropeplea viridis, Radix peregra, Radix luteola, Pseudosuccinea columella, and Galba truncatula.[5][6] The Australian Lymnaea tomentosa (host of F. hepatica) was shown to be receptive to miracidia of F. gigantica from East Africa, Malaysia, and Indonesia.[4]

Definitive hosts

F. gigantica is a causative agent (together with F. hepatica) of fascioliasis in ruminants and in humans worldwide.[4]

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

Infection and pathogenicity

Infection with Fasciola spp. occurs when metacercariae are accidentally ingested on raw vegetation. 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. Eggs are passed through the bile ducts into the intestine, where they are then passed in the feces.[4]

Diagnosis

Despite the importance to differentiate between the infection by either fasciolid species, due to their distinct epidemiological, pathological, and control characteristics, unfortunately, coprological (excretion-related) or immunological diagnoses are difficult. Especially in humans, specific detection by clinical, pathological, coprological, or immunological methods are unreliable. Molecular assays are the only promising tools, such as PCR-RFLP assay,[3][7] and the very rapid loop-mediated isothermal amplification (LAMP).[8]

Treatment

Triclabendazole is the drug of choice in fasciolosis, as it is highly effective against both mature and immature flukes. Artemether has been demonstrated in vitro to be equally effective.[9] Though slightly less potent, artesunate is also useful in human fasciolosis.[10]

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References

This article incorporates CC-BY-3.0 text from references.[4][11]

Cobbold, T. S. (1855). Description of a new trematode worm (Fasciola gigantica). The Edinburgh New Philosophical Journal, Exhibiting a View of the Progressive Discoveries and Improvements in the Sciences and the Arts. New Series, II, 262–267.
Itagaki T, Ichinomiya M, Fukuda K, Fusyuku S, Carmona C (2011). "Hybridization experiments indicate incomplete reproductive isolating mechanism between Fasciola hepatica and Fasciola gigantica". Parasitology. 138 (10): 1278–1284. doi:10.1017/S0031182011000965. PMID 21767436.
Rokni MB, Mirhendi H, Mizani A, Mohebali M, Sharbatkhori M, Kia EB, Abdoli H, Izadi S (2010). "Identification and differentiation of Fasciola hepatica and Fasciola gigantica using a simple PCR-restriction enzyme method". Experimental Parasitology. 124 (2): 209–213. doi:10.1016/j.exppara.2009.09.015. PMID 19769969.
Soliman, MF (1 June 2008). "Epidemiological review of human and animal fascioliasis in Egypt". Journal of Infection in Developing Countries. 2 (3): 182–9. doi:10.3855/jidc.260. PMID 19738348.
Correa AC, Escobar JS, Durand P, Renaud F, David P, Jarne P, Pointier JP, Hurtrez-Boussès S (2010). "Bridging gaps in the molecular phylogeny of the Lymnaeidae (Gastropoda: Pulmonata), vectors of Fascioliasis". BMC Evolutionary Biology. 10: 381. doi:10.1186/1471-2148-10-381. PMC 3013105. PMID 21143890.
Dar YD, Rondelaud D, Dreyfuss G (2005). "Update of fasciolosis-transmitting snails in Egypt (review and comment)". Journal of the Egyptian Society of Parasitology. 35 (2): 477–490. PMID 16083061.
El-Rahimy HH, Mahgoub AM, El-Gebaly NS, Mousa WM, Antably AS (2012). "Molecular, biochemical, and morphometric characterization of Fasciola species potentially causing zoonotic disease in Egypt". Parasitology Research. 111 (3): 1103–111. doi:10.1007/s00436-012-2938-2. PMID 22638917.
Ai L, Li C, Elsheikha HM, Hong SJ, Chen JX, Chen SH, Li X, Cai XQ, Chen MX, Zhu XQ (2010). "Rapid identification and differentiation of Fasciola hepatica and Fasciola gigantica by a loop-mediated isothermal amplification (LAMP) assay". Veterinary Parasitology. 174 (3–4): 228–233. doi:10.1016/j.vetpar.2010.09.005. PMID 20933335.
Shalaby HA, El Namaky AH, Kamel RO (2009). "In vitro effect of artemether and triclabendazole on adult Fasciola gigantica". Veterinary Parasitology. 160 (1–2): 76–82. doi:10.1016/j.vetpar.2008.10.027. PMID 19036519.
Hien TT, Truong NT, Minh NH, Dat HD, Dung NT, Hue NT, Dung TK, Tuan PQ, Campbell JI, Farrar JJ, Day JN (2008). "A randomized controlled pilot study of artesunate versus triclabendazole for human fascioliasis in central Vietnam". American Journal of Tropical Medicine and Hygiene. 78 (3): 388–392. PMID 18337331.
Onocha P. & Otunla E. (2008). "Biological activities of extracts of Pycnanthus angolensis (Welw.) Warb". African Journal of Traditional, Complementary and Alternative medicines, Abstracts of the world congress on medicinal and aromatic plants, Cape Town, November 2008. abstract Archived 2012-03-12 at the Wayback Machine