Phylum: Platyhelminthesclass:Trematoda

ByAssist. lecturer Maytham A. Alwan

Phylum:PlatyhelminthesClass: Trematoda

• General characteristics:1.The class Trematoda falls into two main subclasses, the

Monogenea, which have a direct life cycle, and the Digenea, which require an intermediate host.

2. The adult digenetic trematodes, commonly called `flukes', occur primarily in the bile ducts, alimentary tract and vascular system.

3. Most flukes are flattened dorsoventrally, have a blind alimentary tract, suckers for attachment.

TrematodaGeneral characteristics

4.Depending on the predilection site, the eggs pass out of the final host, usually in faeces or urine, and the larval stages develop in a molluscan intermediate host. For a few species, a second intermediate host is involved, but the mollusc is essential for all members of the group.

TrematodaGeneral characteristics

5. The trematodes are usually hermaphrodite and both cross- and self-fertilization may occur. The male reproductive system consists of a pair of testes each leading into a vas deferens: these join to enter the cirrus sac containing a seminal vesicle and the cirrus.

TrematodaGeneral characteristics

The female system has a single ovary leading into an oviduct which is expanded distally to form the ootype. There the ovum acquires a yolk from the secretion of the vitelline glands and ultimately a shell. As the egg passes along the uterus, the shell becomes hardened and toughened and is finally extruded through the genital opening adjacent to the ventral sucker. The mature egg is usually yellow because of the tanned protein shell and most species have an operculum.04/22/23 5

Trematoda 6. Food, generally blood or tissue debris is ingested and

passed into the ceca where it is digested and absorbed.7. lifecycle: The adult flukes are always oviparous and lay

eggs with an operculum. In the egg the embryo develops into a pyriform (pear-shaped), ciliated larva called a miracidium sporocyst

(in snails ) metacercaria cercariae Rediae(on water plants)

Trematoda:platyhelminthes

Kingdom: animaliaPhylum: platyhelminthesClass: trematodaFamily: fasciolidaeGenus: fasciolaSpecies: Fasciola hepatica, F. gigenticaDisease: FascioliasisHabitate : bile duct of liverCommon name: sheep liver flukeInfective stage : metacercaria on vegetation or grass(water plants)

Fasciola hepatica

Definitive host:Sheep, CattleHumans (Accidental)Other Mammals

Intermediate hostFresh Water Snail(Lymnaea truncatula)

Morphology

• Adult fluke– Flat leaf like body– 20-30mm long– 8-15mm wide

section of F. hepatica adult worm in bile duct

Fasciola hepatica adult 20 – 30 mm L. X 8 – 13 mm B, ( grey – brown )

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Fasciola hepatica adult

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Fasciola hepatica adult

LifecycleLife Cycle:As shown below, Fasciola parasites develop into adult flukes in the bile ducts of infected mammals, which pass immature Fasciola eggs in their feces. The next part of the life cycle occurs in freshwater. After several weeks, the eggs hatch, producing a parasite form known as the miracidium, which then infects a snail host. Under optimal conditions, the development process in the snail may be completed in 5 to 7 weeks; cercariae are then shed in the water around the snail. The cercariae lose their tails when they encyst as metacercariae (infective larvae) on water plants. In contrast to cercariae, metacercariae have a hard outer cyst wall and can survive for prolonged periods in wet environments.

life cycle of Fasciola hepatica

EggEgg

eggs of fasciola hepatica, large, operculated, ovoid in shape contains a large un segmented ovum in amass of yolk cells, 130 – 150 X 63 – 90 µm, light brown to yellow ( bile stained ) from stool smear, duodenal aspirates.

RediaesporocystsMiracidium

CercariaMetacercaria

stages from Fasciola hepatica life cycle