Helminths ( Trematoda ) - PowerPoint Presentation

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Helminths

(Trematoda)

Assis.Prof.Dr

. Suhad Faisal

Hatem

Helminths

(Trematoda)

Helminth

:

commonly known as

parasitic worms

, are large

multicellular

organisms, which when mature can generally be seen with the naked eye including

 two-phyla

:

1. Phylum:

Platyhelminths

(flat worms)

2. Phylum:

Nemahelminths

or

Nematoda

(true round worms).

Platyhelminths

includes

:

1-Class:

Trematoda

)

Flukes

(

2-Class:

Cestoda

)

Tape worms

(

3

-

Turbellaria

Trematoda

class

also classified to groups according to the presence of the adult fluke in the host's body into:

1. Liver (or hepatic) flukes, ex:

Fasciola

hepatica

.

Clonorchis

sienensis

2. Intestinal flukes ex:

Fasciolopsis

buski

,

Heterophyes

heterophyes

3. Blood flukes, ex:

Schistosomes

4. Lung flukes, ex:

Paragonimus

westermani

Morphology and anatomy of

Fasciola hepatica Fasciola

hepatica

is one of the largest

flukes

of the world, reaching a length of 30 mm and a width of 13 mm,

Fasciola

gigantica

, on the other hand, is even bigger and can reach up to 75 mm

).

It is leaf-shaped, pointed at the back (

posteriorly

) and wide in the front (

anteriorly

). The

oral sucker

is small but powerful and is located at the end of a cone-shape projection at the anterior end

.

The

acetabulum

is a larger sucker than the oral sucker and is located at the anterior end

.

Adults of liver flukes are localized in the

liver

of various

mammals

, including

humans.These

flat worms

can occur in

bile ducts

,

gallbladder

, and

liver

parenchyma

. They feed on

blood

. Adult flukes produce eggs which are passed into the

intestine

. It depends on intermediate host (a snail) to complete its life cycle. The intermediate host is the

Lymnaea

genus of snail which lives in marshy areas and standing water

.

Fasciolosis

:

is a

parasitic worm

infection caused by the common liver fluke

Fasciola

hepatica

as well as by

Fasciola

gigantica

.

Pathogensis

Acute

fascioliasis

The acute clinical syndrome of

Fasciola

hepatica

infection occurs during migration of the fluke larvae to the liver parenchyma, with resultant inflammation and localized destruction of liver cells. Once in the bile ducts, liver flukes of all species produce inflammation due to mechanical irritation and toxic

secretions.

In its severe form it occurs in sheep but rarely in man and requires large numbers of parasites, usually over 10,000, to be ingested. Large numbers of migrating larvae invade the liver and cause a traumatic hepatitis that is frequently fatal. Sometimes the liver capsule may rupture into the peritoneal cavity, causing death from peritonitis

.

More usually the invasive phase lasts many weeks, with the most common symptoms being intermittent fever,

hepatomegaly

, and abdominal pain, malaise, wasting,

urticaria

and

eosinophilia

are usual.

Chronic

fascioliasis

This phase may develop months or years after initial infection, when the infection is asymptomatic.

Adult flukes in the bile ducts cause inflammation and hyperplasia of the epithelium. The resulting

cholangitis

and

cholecystitis

, combined with the large body of the flukes, are sufficient to cause mechanical obstruction of the

biliary

duct.This

lead to

biliary

colic

,

epigastric

pain, fatty food intolerance, nausea, jaundice,

pruritus

, right upper-quadrant abdominal tenderness.

Hepatic enlargement may be associated with an enlarged

spleen

or

ascites

Chronic inflammation is connected to increased cancer rates

.

Diagnosis

1- By finding yellow-brown eggs in the

stool.The

eggs pass through the body and out via the

faeces

.

2-An

enzyme-linked

immunosorbent

assay (ELISA) test

is the diagnostic test of choice. ELISA is available commercially and can detect anti-hepatica

antibodies

in serum and milk;

Proteases

secreted by

F. hepatica

have been used experimentally in immunizing antigen.

3- Radiological methods can detect lesions in both acute and chronic infection, while

laparotomy

will detect lesions and also occasionally eggs and live worms.

4-

biopsy

of liver, and gallbladder punctuate can also be used.

Treatment

1-Triclabendazole 2-protein-rich diet are recommended. Iron and vitamins may be required.

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