Raed Z. Ahmed, Medical Parasitology Lab.,2012. Fasciola hepatica Fasciola hepatica lives in the liver of man. Fasciola spp. have many stages: Oval eggs.

Raed Z. Ahmed, Medical Parasitology Lab.,2012


Fasciola hepaticaFasciola hepatica• Fasciola hepatica lives in the liver of man.

• Fasciola spp. have many stages:

• Oval eggs have miracidium, cercaria, metcercaria, larvae and adult stage.

• Intermediate host: Snail.

• Definitive host: Sheep.

• Infective stage (human): Metacercaria.

• Human infected by ingestion metacercaria from infected sheep.

• Diagnosis:

– Stool analysis to find Fasciola egg.


Fasciola hepatica EggFasciola hepatica Egg


Fasciola hepatica MiracidiumFasciola hepatica Miracidium


Fasciola hepatica cercariaeFasciola hepatica cercariae


Fasciola hepatica rediae larvaeFasciola hepatica rediae larvae


Fasciola hepatica AdultFasciola hepatica Adult




Schistosoma sppSchistosoma spp..• Also known as bilharzia, cause schistosomiasis or bilhariziasis.

• Schistosoma spp. have 4 stages:

– Eggs, miracidia, cercaria, and adult stage.

• Eggs are passed through urine or feces to fresh water, where larvae stage can infect a new host by penetrating the skin.

• Schistosoma eggs are non- operculated but spined and have miracidum. Eggs hatch and release miracidia in water.

• Miracidia move in water looking for a special snail, and penetrate a snail tissue and developed to sporocyst.

• Cercaria releasaed by snail into water and free swimming, cercaria has a bifid tail and penetrate intact skin

• Cercaria lose tail during penetration and become schitosomulae, that circulate in the blood and migrate to portal blood of liver and mature into adult.


Schistosoma spp. Schistosoma spp. (cont….)

• There are three medically important species:

– Schistosoma mansoni, lives in the mesenteric venules of large intestine, and cause intestinal bilharziasis.

– Schistosoma japonicum, lives in the mesenteric venules of small intestine.

– Schistosoma haematobium, lives in the venous plexus of the urinary bladder and cause schistosomal hematuria or urinary bilhariziasis.

• S. mansoni and S. japonicum are produce their eggs in stool, but S. haematobium produce eggs in urine.


Schistosoma spp. Schistosoma spp. (cont….)

• Intermediate host: snail.• Definitive host: human.• Cercaria is the infective stage but eggs are the diagnostic

stage.• Diagnosis:

Depends on finding the characteristic ova in feces or urine. Three species can be distinguished by the appearance of

their eggs under microscope:• S. mansoni eggs have prominent lateral spine.• S. japonicum eggs have a very small round lateral spine.• S. Haematobium eggs have a terminal spine.


Snail for Snail for Schistosoma sppSchistosoma spp..


SnailSnail


Oncomelania spp.Biomphalaria spp.

Bulinus spp.

Schistosoma spp. Schistosoma spp. EggsEggs


S. japonicumS. haematobiumS. mansoni

Lateral spine

Terminal spine Rounded spine

Schistosoma Schistosoma miracidiummiracidium


Schistosoma cercariaSchistosoma cercaria


Bifid tail

Oval head

Schistosoma Schistosoma adult maleadult male


Adult male short, thick and have gyanchophoric canal

Schistosoma Schistosoma adult femaleadult female


Adult female longer and thinner than adult male.

Raed Z. Ahmed, Medical Parasitology Lab.,2012. Fasciola hepatica Fasciola hepatica lives in the liver of man. Fasciola spp. have many stages: Oval eggs.

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