| Fasciola gigantica | |
|---|---|
 | |
| Cobbold's drawings of dorsal (left) and ventral views ofFasciola gigantica | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Platyhelminthes |
| Class: | Trematoda |
| Order: | Plagiorchiida |
| Family: | Fasciolidae |
| Genus: | Fasciola |
| Species: | F. gigantica |
| Binomial name | |
| Fasciola gigantica | |
Fasciola gigantica is a parasiticflatworm of theclassTrematoda, which causes tropicalfascioliasis. It is regarded as one of the most important singleplatyhelminthinfections ofruminants inAsia andAfrica. The infection is commonly called fasciolosis.
The prevalence ofF. gigantica often overlaps with that ofFasciola hepatica, and the two species are so closely related in terms ofgenetics, behaviour, andmorphological andanatomical structures that distinguishing them is notoriously difficult.[2] Therefore, sophisticated molecular techniques are required to correctly identify and diagnose the infection.[3]
Fasciola gigantica causes outbreaks in tropical areas ofSouth Asia,Southeast Asia, and Africa. The geographical distribution ofF. gigantica overlaps withF. 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 thepharaohs.[4]
The lifecycle ofF. 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.
As with other trematodes,Fasciola spp. develop in amolluscanintermediate host. Species of thefreshwater snails from the familyLymnaeidae are well known for their role as intermediate hosts in the lifecycle ofF. gigantica; however, throughout the years, an increasing number of other molluscan intermediate hosts ofF. gigantica have been reported.[4] The lymnaeid intermediate hosts ofF. gigantica are distinguishable from those ofF. hepatica, both morphologically and as to habitat requirement. The species ofFasciola can become adapted to new intermediate hosts under certain conditions at least based on laboratory trials. The most importantintermediate host forF. gigantica isRadix auricularia. However, other species are also known to harbour the fluke, includingLymnaea rufescens andLymnaea acuminata in theIndian subcontinent;Radix rubiginosa andRadix natalensis inMalaysia and Africa, respectively; and the synonymousLymnaea cailliaudi in East Africa. Other snails also serve as natural or experimental intermediates, such asAustropeplea ollula,Austropeplea viridis,Radix peregra,Radix luteola,Pseudosuccinea columella, andGalba truncatula.[5][6] The AustralianLymnaea tomentosa (host ofF. hepatica) was shown to be receptive to miracidia ofF. gigantica from East Africa, Malaysia, and Indonesia.[4]
F. gigantica is a causative agent (together withF. hepatica) of fascioliasis inruminants and in humans worldwide.[4]
Theparasite commonly infects cattle and buffalo, and can also be seen regionally in goats and sheep, and in nonruminants (donkeys).
Infection withFasciola spp. occurs whenmetacercariae are accidentally ingested on raw vegetation. The metacercariae exist in thesmall intestine, and move through the intestinal wall andperitoneal cavity to theliver, where adults mature in thebiliary ducts of the liver. Eggs are passed through the bile ducts into the intestine, where they are then passed in the feces.[4]
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) orimmunological 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 asPCR-RFLP assay,[3][7] and the very rapidloop-mediated isothermal amplification (LAMP).[8]
Triclabendazole is the drug of choice in fasciolosis, as it is highly effective against both mature and immature flukes.Artemether has been demonstratedin vitro to be equally effective.[9] Though slightly less potent,artesunate is also useful in human fasciolosis.[10]
This article incorporates CC-BY-3.0 text from references.[4][11]
