Echinococcosis is caused by the tissue-invasive larval stage of the tapeworm Echinococcus. Three main species can infect humans: E. granulosus, E. vogeli, and E. multilocularis. E. granulosus causes cystic hydatid disease, forming fluid-filled cysts in organs. Its life cycle involves canine definitive hosts and ungulate intermediate hosts. Humans are accidental dead-end hosts. The cysts grow slowly and can cause pressure effects or spread following rupture. Diagnosis involves imaging and serology tests. Treatment involves surgery and anti-parasitic drugs.

1. ECHINOCOCCOSIS

2. Classification
• Class: Cestoda
• Genus: Echinococcus
• Species:
Species Diseases
E. granulosus Hydatid disease
Echinococcus vogeli Hydatid disease
E. multilocularis Alveolar hydatid disease

3. Overview
• These are tissue invasive parasites (larval
Cestodes) that invade the major tissues and
organs of the human body and cause a major
disease called Ecchinococcosis (cystic hydatid )
disease.
• Accidental hosts: Humans (Dead end hosts)

4. Reservoirs
Hosts Examples
Definitive
hosts
Canids (canines); dogs, wolves and
(fenines) cats.
Intermediate
hosts
Herbivores like sheep, deer, goats,
horses, cattle, wallabies, kangaroos
and pigs that graze on grass infected
with the eggs of the parasite.
Accidental Humans (Dead end hosts)

5. Farm-dog to sheep cycle Wild ‘reservoir’ cycle
In Australia……
(Where it Echinococcus granulosus is most prevalent)

6. Disease:
Cystic Ecchinococcosis
E. granulosus

7. Morphology
• Size (adult): Ranges in length from 2mm to
9mm
• Segments: Has 3 proglottids (segments) –
immature, mature & a gravid link that is
longer and wide.
• Shape: The scolex (head) has 4 suckers and a
rostellium with hooks (25 – 50 )hooks with a
double crown at the tip of the scolex.

8. Ecchinococcus Granulosus

10. Hydatid brood capsule with
protoscolices

11. Scolex showing hooks

12. E. granulosus immature proglottid.
(Source: CDC)

13. Immature progloid

14. onchosphere

15. Egg of E. granulossus

16. Epidemiology
• World widely spread in the sheep, cattle, pigs
and dog rearing countries in Africa, Central
Asia, southern South America, The
Mediterranean, the middle East and Australia.
In Africa it is found among the Turkana in
Kenya, Ethiopia, Sudan, Northern Uganda and
South Africa.

17. Mode of spread

18. Epidemic Areas
Central Europe South America
Mediterranean countries Middle East
Australia & New Zealand South Africa

19. Life Cycle

20. Lifecycle cont.
• The disease cycle begins when the adult tapeworm gains entry and
attaches itself to the gut of the definitive host usually a carnivore
and can be a canine (dog ) or the feline (cat) lineage.
• Infection begins when the dog eats wastes that contain hydatid
cysts. The swallowed cysts burst and the tapeworm heads travel to
the gut and attach themselves to the intestine wall. The worms are
mature after about 6 weeks and an adult worm is only 6mm in
length. Each mature worm grows and sheds the last segment of its
body about every 2 weeks. The last segment contains immature
eggs. The eggs are passed from the animal’s body in fecal material
into the soil, that is eaten by an intermediate host. The eggs are
resistant to weather conditions and can remain visible for months.

21. cont
• The intermediate host usually grazing animals
in areas where canids also exist eat the grass
infected with the tapeworm eggs. The eggs
hatch in the animals gut into embryos called
oncosphere larvae that contain hooks that
travel through the blood stream and attack
vital organs like the liver, lungs, brain, bones,
kidney, spleen and form unilocular hydatid
cysts in the host’s tissues.

22. Cont,
• The hydatid cysts are bladder like structures
where brood (breeding) capsules are formed and
are sometimes attached to a mother cyst. These
cysts contain around 30 to 40 tapeworms. These
cysts can grow and enlarge to the size of a
softball or basket ball and may contain several
smaller “balloons.” inside the main cyst via
asexual reproduction they give rise to
protoscolex(precursors to the head of a
tapeworm) and daughter cysts. In humans
protoscoleces are rarely produced in those who
are infected.

23. E. granulossus cyst
• Slow development of cyst
• Cysts have thick-walled chambers
• Separated by connective tissue
• Cyst is fluid filled
• Cyst is free of host material

24. Unilocular hydratid cyst

25. LIFE CYCLE
• Definitive host eats the infected organs and becomes
infected
• After ingestion, the protoscolices evaginate, attach to the
intestinal mucosa and develop into adult stages (scolex and
adult tapeworm)
• In 32-80 days, the cycle starts over when a canid eats
infected meat and passes out eggs.
• The four stages involved in adult maturation are
proglottisation, maturation, growth and segmentation.
Proglottisation and maturation form the reproductive units.
Growth and segmentation lengthen the body.
• Humans can be exposed to these eggs by “hand to mouth”
transfer or contamination. By ingesting food, water or soil
contaminated with stool from infected dog. This might
include grass, herbs, greens or berries gathered from fields
and by getting or handling dogs infected with the disease.

26. Life Cycle (cont’d)

27. Clinical manifestations
• Cysts may develop in any area of the body but the lungs and liver are
most frequently impacted, followed by organs of the central nervous
system.
• A liver cyst may produce no symptoms for 10 -20 years until its large
enough to be felt by physical examination. Symptoms include:
• Pain or discomfort in the upper abdominal region or chest due to the
presence of the tapeworm.
• Nausea and vomiting or coughing may occur as a result of the growing
cysts.
• Unexplained weight loss.
• Rupture of cyst can lead to allergic reactions, anaphylatic shock and a
hypersensitive reaction due to a flood of foreign material in the body that
can result in death.
• Pressure of the cyst on surrounding tissue or bones may lead to blindness,
collapse of infected bones or even sudden death if the cyst is in the heart.

28. Pathophysiology
• Hydatid disease or echinococcosis can be either
primary (spread by ingestion) or secondary (larval
tissue proliferates after spread from the primary
site - usually from trauma). In primary
echinococcosis larval cysts develop in a single
organ in most cases (about 80% of cases). About
70% of cases involve the liver. The cysts have a
wall made from both host tissue (pericyst) and
larval origin (endocyst) The cysts are fluid-filled
and grow very slowly (about 1 cm in diameter
every year).

29. Cont.
• The expanding hydatid cyst causes pressure
necrosis of surrounding tissues, although as
growth is slow a good deal of accommodation
may take place before any vital structures are
compromised. This depends on the location of
the cyst.

30. Cont.
• Slow leakage of hydatid fluid from the cyst
sensitizes the patient and elicits eosinophilia.
• Rupture of an abdominal hydatid cyst either
through trauma or in the course of surgery,
carries with it both the risk of anaphylatic
shock and the possibility of spread of the
germinal epithelium which are capable of
producing a new cyst.

31. • Rupture of a pulmonary cyst into a bronchus
may be marked by severe allergic symptoms
and coughing with the production of blood
flecked fluid which may contain recognizable
hydatid tissue. At times this results in
spontaneous cure, but secondary infection
may lead to chronic lung abscess.

32. Cystic hydratid disease

33. DIAGNOSIS
• C T scan for abdominal thoracic cysts.
• X- ray tests.
• Radiographic examination
• Serological tests
• Detection of Antigens in faces by Elisa is currently the
best technique.
• New techniques like PCR is also used to identify the
parasite from DNA isolated from eggs or feaces.

34. PREVENTION
• Health education in areas where the disease is known to
occur about basic hygienic practices.
• De-worming dogs on a routine basis to prevent spread of
the disease.
• Make it a practice to feed dogs with only commercially
prepared dog foods from reputable manufacturers
• Do not feed raw or infected offal waste meats that include
organs and entrails to a dog.
• Wash hands before eating, drinking and smoking and after
gardening or handling animals or their pens.
• Children should avoid direct contact with dogs and
indirectly through soil, water and contaminated vegetables
and teach them to wash hands.

35. TREATMENT
• Surgery taking special care to leave the cyst
intact so that new cysts do not form.
• Mebendazole over along period of time at low
dosages.
• Albendazole
• Praziquantel.

36. Medication
Praziquantel
Arecoline
Surgery

37. Differences in Cysts
Echinococcus granulosus
• Slow development of cyst
• Cysts have thick-walled
chambers
• Separated by connective
tissue
• Cyst is fluid filled
• Cyst is free of host material
Echinococcus multilocularis
• Rapid development of cyst
• Cyst has thin-walled
chambers
• Not separated by
connective tissue
• Cyst is gelatinous filled
• Cyst is contaminated by
host material