Fasciola hepatica DR.SHIVANI GUPTA, PGGCG-11, CHANDIGARH

Classification Kingdom: Animalia Phylum: Platyhelminthis Class: Trematoda Order: Echinostomida Family: Fasciolidae Genus: Fasciola Species: F. hepatica Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic flatworm of the class Trematoda, phylum Platyhelminthes that infects liver of various mammals, including humans. The disease caused by the fluke is called fascioliasis (also known as fasciolosis). F. hepatica is distributed worldwide and causes great economic losses in sheep and cattle.

wall of the primary host. Morphology -Dark red in colour. -Approx. 3cm long and 1.5cm wide. -Body is flat and leaf like. -Body has an oral sucker that surrounds the mouth and a ventral sucker, both serve to attach the fluke to the tissue of the primary host -Body is surrounded by a thick protective cuticle. -Cuticle bears many spines to attach to the wall of the primary host. -There is a genital pore for reproduction between the two suckers.

Digestive System -The anterior portion or pharynx has strong muscular walls, which, in conjunction with protractor and retractor muscles, bring about a kind of pumping action whereby nutritive fluids are taken in. -The canal, which leads from the posterior end of the pharynx, divides almost immediately into two branches, which diverge at first rapidly and then run almost parallel, as far as the hinder end of the body. -Each of these gives off from its outer aspect some 16 or 17 lateral branches, which divide and subdivide till their ramifications fill nearly the whole area of the body.

Nervous System The brain is a bilobed cerebral ganglion dorsal to the esophagus. Three pairs of longitudinal nerve cords (dorsal, lateral, and ventral) exit the brain and are connected with each other by numerous transverse commissures.

Male Reproductive System -The male system begins with two large, irregularly branched testes located in the posterior third of the worm . -One is the anterior testis and the other the posterior testis. -A slender vas efferens arises near the center of each testis. -The two vasa efferentia unite near the middle of the body to form the short vas deferens. -The vas deferens quickly widens to become the muscular seminal vesicle. -The tube extends anteriorly and eventually joins the uterus and the two open together to the exterior via the common gonopore.

Female Reproductive System -The single germarium (ovary) lies on the midline immediately anterior to the seminal receptacle. -The ootype is a glandular chamber near the center of the worm. -The germarium connects with the ootype via the oviduct. -The two large vitellaria produce vitellocytes (= yolk cells). They lie lateral to the intestinal ceca, between the ceca and the edge of the body. Each is drained by a large vitelline duct (= vitellarium duct). -The two ducts join each other to form a short common duct that delivers vitellocytes to the ootype. -The large brown uterus exits the ootype and extends anteriorly to its union with the seminal vesicle at the common gonopore.

Life Cycle -The adult flukes (Fasciola hepatica: up to 30 mm by 13 mm; F. gigantica: up to 75 mm) reside in the large biliary ducts of the mammalian host. Immature eggs are discharged in the biliary ducts and in the stool. -After development in water, each egg releases a miracidium which invades a suitable snail intermediate host. -In the snail the parasites undergo several developmental stages (sporocysts, rediae, and cercariae). -The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other surfaces. -Mammals acquire the infection by eating vegetation containing metacercariae. -After ingestion, the metacercariae excyst in the duodenum and migrate through the intestinal wall, the peritoneal cavity and the liver parenchyma into the biliary ducts, where they develop into adults. -Fasciola hepatica infect various animal species, mostly herbivores. -Humans can become infected by ingesting metacercariae-containing freshwater plants, especially watercress. -In humans, maturation from metacercariae into adult flukes takes approximately 3 to 4 months.

Life Cycle

Life Cycle

Fasciola- Larval stages Egg Miracidia Cercariae Metacercariae