CestodesTapeworms

- are segmented worms

- The adults reside in the gastrointestinal tract, but the larvae can be found in almost any organ

- Human tapeworm infections can be divided into two major clinical groups:

In one group, humans are the definitive hosts, the adult tapeworms live in the gastrointestinal tract (Taenia saginata, Diphyllobothrium, Hymenolepis, and Dipylidium caninum). In the other, humans are intermediate hosts, and larval-stage parasites are present in the tissues.

Echinococcosis Hydatid desease Echinococcosis of humans is caused by the larval stage of Echinococcus granulosus

- ECHINOCOCCUS GRANULOSUS GRANULOSUS- ECHINOCOCCUS GRANULOSUS BOREALIS- ECHINOCOCCUS GRANULOSUS CANADIENSIS- ECHINOCOCCUS GRANULOSUS EQUINUS 

E. granulosus produces unilocular cystic lesions

E. granulosus is prevalent in areas where livestock is raised in association with dogs.

E. granulosus is found in: Australia, Argentina, Chile, Africa, eastern Europe, the Middle East, New Zealand, and the Mediterranean region, particularly Lebanon and Greece.

E. granulosus is found in: Australia, Argentina, Chile, Africa, eastern Europe, the Middle East, New Zealand, and the Mediterranean region, particularly Lebanon and Greece.

Echinococcal species have 2 hosts:• intermediate and • definitive hosts

1. Definitive hosts are dogs,

that pass eggs in their feces

2. Intermediate hosts are:• sheep, cattle, humans, goats,

camels, and horses

Etiology

Adult E. granulosus is a

small (2,7-5 mm long) cestode,

which lives for 5 to 20 months

in the jejunum of dogs, чакал, вълк,

He has scolex with hookless,

only 3-4 proglottids –

immature, mature, and gravid (400 — 800 eggs)

After humans

ingest the eggs,

embryos escape

from the eggs,

penetrate the

intestinal

mucosa, enter

the portal

circulation,

and are carried

to organs.The life cycle iscompleted whena dog ingestslamb

containingcysts 

Larvae develop into

fluid-filled unilocular

hydatid cysts that

consist of an external

membrane and an inner

germinal layer.

Daughter cysts

develop from the inner

aspect of the germinal

layer, as do germinating

cystic structures called

Brood capsules.

New

larvae,

called

scolices,

develop in large

numbers within

the brood

capsule.

Clinical Manifestations

1. Slowly enlarging EC generally remain asymptomatic, until their expanding size or their space-ccupying effect in an involved organ elicits symptoms.  

Since a period of 5 - 20 years EC may be discovered incidentally

on a routine x-ray or US study.

2. Rupture can occur: spontaneously or at surgery .

Cysts may involve any organ.

The liver

and

The lungs

are

the

Most common

sites.

55

25

632,5

0

10

20

30

40

50

60

1st Qtr

ЧЕРНОДРОБНАБЕЛОДРОБНА МОЗЪЧНАСЛЕЗКОВАБЪБРЕЧНА

Cysts may involve any Organ: - bone

- medullary cavity

- the CNS

- the heart

- spleen

Prognosis

Complications:• Mechanical icterus• Cholangitis• Absces• Peritonitis• Empiema• Rupture• Anafilactic chock• Dissemination• Secondary multiplic ech

Recidives (> 30 %)

Letalites 1 до 15 %.

Diagnosis

Radiographic and related imaging

studies are important in detecting

and evaluating echinococcal cysts.

X-ray will define pulmonary cysts:

- usually as rounded, uniform

density

- but may miss other cysts in other

organs unless there is cyst wall

calcification (as occurs in the liver).

Pathognomonic finding is:

-daughter cyst within the larger cyst.

-eggshell or mural calcification

Thise findings on CT,

is indicative of E.G.

invasion and helps to

distinguish from

carcinomas, bacterial

or amebic liver

abscesses, or

hemangiomas.

A specific diagnosis can be made

by:

the examination of aspirated

fluids for scoliceal hooklets, but

diagnostic aspiration is not

conventionally recommended

because of the risk of fluid leakage

resulting in either dissemination or

anaphylactic reactions.

Serodiagnostic assays

Serodiagnostic methods are:• HAT, positive titres 1: 200• ELISA, positive titres 1: 200• IFA positive titres 1: 20• immunoblotting test

Serodiagnostic assays can be a negative

(up to 30 % of patients may have negative

resultes), but does not exclude the diagnosis

of echinococcosis.

TREATMENT

Therapy for echinococcosis is based on considerations of the size, location, and manifestations of cysts and the overall health of the patient.

• Surgery, when feasible, is the principal definitive method of treatment; E. granulosus cysts are excised.

• Risks at surgery from leakage of fluid include anaphylaxis and dissemination of infectious scolices. The latter complication has been minimized by the instillation of scolicidal solutions such as hypertonic saline or ethanol, which may cause hypernatremia, intoxication, or sclerosing cholangitis.

Chemotherapy• As medical therapy, albendazole, given at a

dose of:• 10-15 mg/kg/day for 30 days, with 15 days

intervals or• 400 mg twice a day for 12 weeks,

is most efficacious, although multiple courses may be necessary

• Response to treatment is best assessed by repeated evaluation of cysts by CT or MRI, with particular attention to cyst size and consistency.

Prevention

In endemic areas, echinococcosis can be prevented by:

-         administering praziquantel to infected dogs every 3 months

-         by denying dogs access to butchering sites and to the offal of infected animals.

-         Limitation of the number of stray dogs is helpful in reducing the prevalence of infection among humans.