2. • Hydatidosis: A disease caused by the cyst of the dog tapeworm,
Echinococcus granulosus.
• It is also known as echinococcosis or hydatid disease.
• Echinococcosis is primarily an enzootic disease of dogs that commonly
occurs after eating infected viscera of sheep and other herbivores.
• The dog is the principal definitive host worldwide but other carnivores such
as lion, hyenas and jackals are final hosts.
• Herbivores such as sheep, cattle and pigs are intermediate hosts and
humans are accidental dead end hosts.
3. • Three species of Echinococcus have been generally accepted as parasites
of man namely:
o Echinococcus granulosus; Causing Hydatid Disease
o Echinococcus multilocularis; Causing Alveolar Hydatid Disease
o Echinococcus vogeli; Causing Hydatid Disease.
ƒThe cysts of this species resemble Echinococcus granulosus and are often
thought of as a variant of Echinococcus granulosus.
• This disease is rare but where it exists, it is a persistent public health
problem.
• Typical cases are common where the community lives in semi-arid
environment and have usually close contact with their dogs.
4. Life Cycle of Echinococcus Granulosus
Eggs are passed in the dog’s faeces and ingested by sheep, goats, cattle, camels and
donkeys.
• The eggs hatch in the animal’s intestine, and the larvae penetrate the intestinal wall
and pass into the portal circulation to be carried to the liver and lungs where they form
cysts with many daughter cysts.
• When a dog eats the diseased animal, it is infected by these cysts, which then
proceed to develop into mature worms.
5. • Humans can be exposed to these eggs in two main ways, both of which involve
‘hand-tomouth’ transfer or contamination:
o By directly ingesting contaminated food, including grass, herbs, greens, or
berries gathered from fields.
o By petting or handling household cats and dogs infected with the Echinococcus
tapeworm.
ƒThese pets may shed the tapeworm eggs in their stool, and their fur may be
contaminated.
• People at high risk for Echinococcosis include trappers, hunters, veterinarians,
farmer or others who contact wild animals, or their stool, or household cats and dogs
who have the opportunity to eat wild rodents infected with hydatid disease.
6. Clinical Features of Echinococcosis
• Echinococcosis or hydatid disease is a disease which present with two forms due to
two different causative organisms the Echinococcus granulosus and Echinococcus
multilocularis.
• The clinical presentation of hydatid disease depends on the size and site of the lesion
and the accessibility of the organ involved for clinical examination.
• Pain or discomfort in the abdominal regions, weakness, and weight loss may occur as
a result of the growing cysts.
• If the organ involved is the liver symptoms may mimic those of liver cancer and
cirrhosis of the liver.
7. Echinococcus Granulosus
• Hydatids cysts develop slowly over a period of months to years.
• Slowly enlarging echinococcal cysts generally remain asymptomatic until their expanding size or
their space occupying effect in an involved organ elicits symptoms.
• The enlarging mass lesions produce pain and potentially physical obstruction/pressure on
surrounding organs.
• Hydatid disease of lung or liver is generally asymptomatic but can cause anaphylaxis if rupture of
cyst occurs and dissemination of the ‘daughter’ cysts elsewhere in the body.
• The cysts usually occur in the liver, but almost any tissue in the body can be affected, the lung
being the next commonest site.
• When it occurs in the liver, it enlarges and could be confused with amoebic liver abscess.
• However, the general condition of the patient remains good and there is a high eosinophilia.
8. Echinococcus Multilocularis
• This is rare in Africa.
• The 'cyst' grows invasively by external budding, forming a diffuse growth through the infected organ,
replacing that organs tissue.
• Causes solid, tumor-like masses and is commonly confused with hepatic cirrhosis or carcinoma.
• These are much more aggressive lesions than hydatid cysts because the organism reproduces
asexually by lateral budding and extension into surrounding tissues, rather than into the cyst itself.
• Composed of numerous cavities containing a gelatinous matrix within which protoscolices and
numerous brood capsules are produced, and which in its behaviour, most closely resembles a malignant
neoplasm.
• In contrast to E. granulosus this growth is also very rapid, infective protoscolices being present after
only 2 to 3 months, as compared to the 1 to 2 years.
• Fatality rates in infected humans approach 50%.
9. Management of Echinococcosis
Diagnosis
• When echinococcosis is suspected patient should be referred as soon as
possible.
• At hospital level chest x-ray or abdominal ultrasound investigation can be
done.
• Serological tests if available can also be done to assist in making the
diagnosis.
• It is therefore advisable to refer all suspected cases to hospital for
investigation and advanced management
10. Treatment
• Surgery is the recommended treatment for human disease caused by E granulosus
and E multiloculans.
• However, pre- and post-operative 1-month courses of Albendazole (400 mg twice
daily x 28 days for adults and 15mg/kg per day for children) and 2 weeks of
Praziquantel should be considered in order to sterilize the cyst, decrease the chance of
anaphylaxis, and decrease the tension in the cyst wall (thus reducing the risk of
spillage during surgery) and to reduce the recurrence rate post-operatively.
• Intra-operatively, the use of hypertonic saline or 0.5% silver nitrate solutions before
opening the cavities tends to kill the daughter cysts and therefore prevent further
spread or anaphylactic reaction.
11. • Another method is PAIR (Percutaneous Aspiration, Infusion of scolicidal
agents and Reaspiration of cyst content) albendazole or praziquantel should
be initiated before any procedure and prolonged 28 days if dissemination of
hydatid cyst is to be avoided.
• Medical therapy with albendazole alone in the dose of 400 mg twice daily or
mebendazole has met with varied success.
• This medication may soon be the preferred alternative to surgical
intervention in patients for whom surgery is not an option.
• All these procedures are done at hospital level, do not aspirate cyst at
health centre or dispensary.
12. Prevention of Hydatid Disease
• To control this parasitic infection, it is really important to break the infection cycle by education and public
awareness of the disease and how it is transmitted.
• The following are strategies to prevent echinococcosis, most of which involve disruption of the parasite's life
cycle.
o Basic hygiene practices such as thoroughly cooking food and vigorous hand washing before meals and
after handling pets can prevent the eggs entering the human digestive tract.
o Do not eat wild fruits or vegetables picked directly from the ground without careful washing or cooking.
o Do not feed sheep viscera to dogs or allow them to have access to sheep carcasses
o Don't touch a wild canine, dead or alive, without wearing gloves and washing hands afterward.
o Don't allow cats and dogs to wander or to capture and eat rodents.
o For E. granulosus, control measures include supervision of livestock slaughtering, safe disposal of
infected viscera, dog control and health education.
