Fasciola hepatica is a parasite that infests humans and many species of animals. It is taxonomically classified as belonging to phylum Platyhelminthes (flatworms), under class Trematodea (flukes), and sub class Digenea. F. hepatica is the most common of the genus Fasciola and is prevalent worldwide (Espino & Dumenigo, 539). The trematode is known to cause the disease called Fasciolosis or Fasioliasis in vegetarian animals especially those belonging to the animal husbandry industry such as sheep, goats and cattle.
Humans can also be infected albeit less frequently as ruminant animals and are mostly considered accidental hosts (Yagzan Aksoy et al. , 40). Fasciolosis/fascioliasis is an economically significant disease since the parasite causes the liver of the infected livestock to be declared unsuitable for human consumption while at the same time reduces the quality of milk and meat produced resulting in losses. The disease is already considered the second most important disease to affect the economy (Espino & Dumenigo, 539).
Human infection is only possible if ingestion of the parasite occurs in large numbers. Generally, the infectious route is through ingestion of contaminated aquatic plants such as watercress. Characteristically, Fasciola hepatica is a leaf-shaped trematode that measures about 20-40 mm in length and 15mm in width with its entire surface covered by spine like scales. They usually reside within the bile ducts, causing various designations such as ‘liver rot’ and ‘wormy liver’ (Anonymous, 4; Espino & Dumenigo, 540).
Its anterior end has a conical projection that terminates anteriorly in an oral sucker while; ventrally located, at the base of the cone is a ventral sucker. The posterior end is broad and pointed (Espino & Dumenigo, 540). Fasciola hepatica follows a complex life cycle that involves several hosts. For the cycle to begin/continue, eggs must first be deposited in fresh water through the feces of an infected carrier. After a period of incubation (usually 9-21 days), miracidia will emerge and must then find an intermediate host, usually a snail belonging to the Lymnacidae family.
In this host, the miracidia will transform into a sporocyst that will give rise to primary and secondary rediae. The latter of which will then give rise to the stage known as cercariae that will leave the host snail and swim until it comes into contact with and adhere to the surface of aquatic plants where it will shed off its tail and transform into the infective cyst known as metacercariae and await the next step of the cycle: ingestion (Espino & Dumenigo, 540).