Echinococcus granulosus- causative agent of hydatid disease

1. Dr Muneeb Muhammed Ali
Dr Muneeb Muhammed Ali
Tutor
Nethaji College
Email:muneebmu7@gmail.com

2.  Echinococcus causes hydatid disease.
 There are four species of Echinococcus
known to infect humans.
1. E. granulosus: Causes cystic hydatid
disease
2. E. multilocularis: Causes alveolar
hydatid disease
3. E. vogeli and E. oligarthrus : Cause
polycystic hydatid disease.
Dr Muneeb Muhammed Ali

3. Echinococcus granulosus, also called dog tape
worm or hydatid worm
E. granulosus causes cystic echinococcosis or
hydatid disease in livestock and humans
beings which acts as intermediate hosts and
parasitize the small intestines of adult canids i.e.
definitive hosts.
It is a zoonotic disease.
Dr Muneeb Muhammed Ali

4. • The disease is prevalent in most parts of the world,
though it is most extensive in the sheep and cattle
raising areas of Australia, Africa, and SouthAmerica.
• It is also common in Europe, China, the Middle East
and India.
• It is seen more often in temperate than in tropical
regions.
Dr Muneeb Muhammed Ali

5. • The adult worm lives in the jejunum and
duodenum of dogs and other canine
carnivora (wolf and fox).
• The larval stage (hydatid cyst) is found in liver
and other visceral organs of humans and
herbivorous animals (sheep, goat, cattle and
horse)
Dr Muneeb Muhammed Ali

6. Adult worm :
The adult tapeworm ranges in length from 3 mm to
6 mm.
It comprises of a scolex (head) , neck and strobilla
or proglottids consisting of 3 or 4 segments.
The 1st segment is immature , 2nd is mature and the
last one or two is gravid.
The terminal segment is by far the biggest (2-3mm x
0.6mm)
The scolex bears four suckers and also has a
rostellum with two rows of hooks.
The neck is short and thick.
Dr Muneeb Muhammed Ali

7. Echinococcus is triploblastic, anus is
absent and it has no digestive system.
Its body is covered by tegument and the worm
is divided into a scolex, a short neck, and
three to six proglottids.
The adult worm lives for 6–30 months
Egg :
ovoid in shape and resembles other taenia.
Measures 32-36 μm x 25-32 μm and contains
a hexacanth embryo with 3 pairs of hooks.
Dr Muneeb Muhammed Ali

8. Dr Muneeb Muhammed Ali

9. Dr Muneeb Muhammed Ali

10. • Found within the hydatid cyst developing inside
various organs of the intermediate host.
• Represents the structure of the scolex of adult
worm and remains invaginated within a
vesicular body.
• After entering the definitive host, the scolex
with suckers and rostellar hooklets, becomes
evaginated and develops into adult worm.
Dr Muneeb Muhammed Ali

11. Host: E. granulosus life cycle passes
through two hosts:
1.Definitive host: Dogs and other canine
animals
2.Intermediate host: Sheep and other
herbivores. Man acts as an accidental
intermediate host (dead end).
Mode of transmission: Men (and other
intermediate hosts) acquire the infection by
ingestion of food contaminated with dog’s
feces containing E. granulosus eggs. Rarely
flies serve as a mechanical vector of the
eggs.
Dr Muneeb Muhammed Ali

12. Dr Muneeb Muhammed Ali

13. Eggs transform to larva (hydatid cyst):
 In duodenum of man or sheep and cattle , the
oncosphere is released by the rupture of ova.
 Onchosphere hatches and penetrates into the
intestinal wall, enters the portal circulation and
carries to the liver (60–70% of cases) or lungs or
rarely to other organs.
Host immune response may destroy many
oncospheres, but few may escape destruction and
develop into hydatid cyst.
The oncospheres are encysted by the fibrous tissue
(produced by fibroblasts) and transform into fluid filled
bladder like cyst called as hydatid cysts
Dr Muneeb Muhammed Ali

14. This stage is infective to dog and
other definitive hosts
Man is a dead end (as dogs don’t feed
on human viscera)
Development in Dog
Dog and other canine animals acquire infection
by consumption of the contaminated viscera of
intermediate hosts (sheep and cattles)
containing mature hydatid cysts.
The hydatid cyst (larva) transforms into
adult worm in dog’s intestine.
The adult worm becomes sexually mature, self
Dr Muneeb Muhammed Ali

15. Pathogenicity is related to the deposition of the
hydatid cysts (larval form of the parasite) in
various organs.
Hydatid cyst : Fully developed hydatid cyst of E.
granu losus is unilocular, subspherical in shape
and size varies from few milimeters to more than
30 cm (usual size 5–8 cm).
It appears as fluid filled bladder like cyst.
Dr Muneeb Muhammed Ali

16. Cyst wall consists of three layers:
a. Pericyst (outer layer, host derived): Consists of
fibrous tissue and blood vessels produced by the
host cellular reaction
b. Ectocyst (middle layer, parasite derived): It is a
tough elastic, glycan rich acellular hyaline layer of
variable thickness (1 mm). It resembles the white of a
hardboiled egg
c. Endocyst ( inner layer, parasite derived): Germinal
layer, 22–25 μm thickness. It consists of number of
nuclei embedded in protoplasmic mass. Its function is
Dr Muneeb Muhammed Ali

17. Dr Muneeb Muhammed Ali

18. It is clear, colorless to pale yellow
It has a pH of 6.7 and specific gravity of 1.005 to
1.010
Chemical composition : sodium chloride, sodium
sulfate, sodium phosphate and succinates
It is antigenic, toxic and anaphylactic
Brood capsules : arise from the inner side of the
endocyst and contains number of protoscolices
(future head)
Hydatid sand: Some of the brood capsules and
protoscolices break off and gets deposited at the
bottom as granular deposit to form
Dr Muneeb Muhammed Ali

19. Acephalocyst: Cysts without
brood capsules and
protoscolices
Endogenous daughter cysts: Formed
by the breakage of the brood capsule
into the hydatid fluid; surrounded by
ectocyst and endocyst
Dr Muneeb Muhammed Ali

20. Infection usually occurs in childhood but gets
manifested in adult life.
Site: Most common site of location of the cyst is
liver (60–70%, right lobe) or lung (20–30%) but
may be found in any organs like spleen and
kidney (3–5%), brain and heart (1–1.5%) and
rarely bones
They grow upto 5–10 cm in size within the
first year and can survive for years or even
decades
Asymptomatic: Many cases are asymptomatic
and infection is detected only incidentally by
imaging studies
Dr Muneeb Muhammed Ali

21. Symptoms occur due to:
a. Pressure effect of the enlarging cyst: Leads to
palpable abdominal mass, hepatomegaly,
abdominal tenderness, portal hypertension and
ascites
b. Obstruction: Daughter cyst may erode into the
biliary tree or a bronchus and enter into the
lumen to cause cholestasis and dyspnea
c. Secondary bacterial infection can cause
pyogenic abscess formation in the hydatid
cysts
d. Anaphylactic reactions: Cyst leakage or rupture
may be associated with a severe allergic reaction
to hydatid fluid antigens; leading to hypotension,
syncope and fever
a. Younger children are more associated with
extrahepatic cysts in lungs, brain and orbital sitesDr Muneeb Muhammed Ali

22. Dr Muneeb Muhammed Ali

23. Dr Muneeb Muhammed Ali

24. It is an immediate hypersensitivity reaction to
hydatid fluid antigens. Developed by Casoni in
1911
Antigen used: Sterile hydatid fluid
Procedure: 0.2 mL of the antigen is injected in one arm;
sterile saline is injected to the other arm as control
Interpretation: Sensitive patients develop large wheal
measuring 5 cm or more with formation of pseudopodia
within 30 minutes with no reaction in the control arm
Disadvantage:
It has low sensitivity (60-80%) and gives false positive
results in cross reactive cestode infections
It is obsolete now days and replaced largely by the
serological tests.
Dr Muneeb Muhammed Ali

25. Screening tests: Various antibody detection methods
are evaluated using crude E. granulosus cyst fluid
antigen. They show variable results (60–90%
sensitivity) .These tests are:
a. Indirect hemagglutination (IHA)
b. Latex agglutination test (LAT)
c. Indirect fluorescent antibody tests (IFA)
d. ELISA
Confirmatory tests:
a. Immunodiffusion and electro immunodiffusion
b.Western blot:
Dr Muneeb Muhammed Ali

26. ELISA , CIEP and LAT are available to detect specific
antigens in serum and urine.
Imaging methods : Imaging methods play an
important role as they are noninvasive methods,
which can detect the cysts incidentally in
asymptomatic individuals and in seronegative cases.
a.Xrays: to detect hepatomegaly
b.Ultrasound (USG): detects both single and
multiple cystic lesions
c. Computed tomography (CT scan): It can
detect 90–100% of cases. It detects more accurately
the number,
Dr Muneeb Muhammed Ali

27. Aspirated hydatid fluid is examined for brood
capsules by direct microscopy or staining with
acid fast stain.
Purulent material can be examined after treating
with hydrochloric acid
Histological examination : Surgically removed
cysts can be subjected to histopathological stains
like Giemsa, hematoxylin and eosin (H & E) and
Periodic acid Schiff (PAS) stain to demonstrate the
three layers
Dr Muneeb Muhammed Ali

28. Molecular Methods : PCR
Other tests
Eosinophilia is present in 20–25% cases
Hypergammaglobulinemia.
Dr Muneeb Muhammed Ali

29. Surgical Removal of Hydatid Cyst : 90%
effective but can be risky depending on
location, size, and advancement of cyst
It may need chemotherapy to prevent recurrance
Chemotherapy: Albendazole is preferred
treatment because it penetrates into hyatid
cysts. Dosage: 10mg/kg body
weight or 400mg 2x daily for 4 weeks
Mebendazole Dosage: 40mg/kg body weight
3x daily for 3-6 months
Dogs are effectively treated with Praziquental
Dr Muneeb Muhammed Ali

30. In order to prevent transmission to dogs from
intermediate hosts, dogs can be given
anthelminthic vaccinations
Clean slaughter and high surveillance of potential
intermediate host during slaughter
Proper disposal of carcass and offal after slaughter
to prevent dogs access to offal from livestock
Boiling livers and lungs which contain hydatid cysts
for 30 minutes has been proposed as a simple,
efficient and saving way to kill
Dr Muneeb Muhammed Ali

31. Dr Muneeb Muhammed Ali