Hydatid disease (also known as hydatidosis or echinococcosis) is
caused by a tapeworm which infects dogs, dingoes and foxes. At its
intermediate stage, it forms cysts in the internal organs, especially
livers and lungs, of a number of animals, including humans. In
humans, the disease is so serious that it requires surgery for
treatment. Hydatid disease also causes losses in livestock with the
downgrading of edible meat by-products because of the presence of
the hydatid cysts.
Control of hydatid disease involves the elimination of the hydatid
tapeworm from dogs. By carrying out the recommended control
measures, the infection of dogs with the tapeworm can be
prevented, and the spread of the disease to other animals, including
With better control of hydatid disease in domestic livestock and
dogs, it is the hydatid cycle that occurs in wildlife which is becoming
relatively more important as a threat to human health.
Signs and symptoms.
In the human manifestation of the disease, E. granulosus, E.
multilocularis, E. oligarthrus and E. vogeliare localized in the liver
(in 75% of cases), the lungs (in 5-15% of cases) and other organs in
the body such as the spleen, brain, heart and kidneys (in 10-20% of
cases). In the patients who are infected with E. granulosus and
therefore have cystic echinococcosis, the disease develops as a slow-
growing mass in the body. These slow-growing masses, often called
cysts, are also found in patients that are infected with alveolar and
polycystic echinococcosis. The cysts found in those with cystic
echinococcosis are usually filled with a clear fluid called hydatid
fluid, are spherical and typically consist of one compartment and are
usually only found in one area of the body. While the cysts found in
those with alveolar and polycystic echinococcosis are similar to
those found in those with cystic echinococcosis, the alveolar and
polycystic echinococcosis cysts usually have multiple compartments
and have infiltrative as opposed to expansive growth.
Symptoms are primarily of cholestatic jaundice (about a third) and
epigastric pain (about a third), fatigue, weight loss, hepatosplenomegaly and
Distant metastases are possible, and involvement of other organs (for example, in
the lung, brain, and bone) occurs in as many as 13% of the patients.
Disease in the lung causes cough, hemoptysis, dyspnea and pyrexia.
Disease in the brain causes raised intracranial pressure and can cause epilepsy.
Disease in the vertebrae can lead to compression of the spinal cord, causing
paraplegia. In the long bones it may cause fractures and deformity.
Prevention of hydatid disease in endemic areas
Dog owners should practice good hygiene when handling their animals.
It is important to wash the hands after handling dogs.
Avoid contact with dog faeces.
Prevent dogs from soiling the immediate environment.
Prevent dogs from roaming or having access to raw sheep meat or viscera.
All sheep carcasses should be disposed of correctly and immediately.
All dogs, especially those in rural endemic areas should be treated at six-weekly
intervals with a wormer containing praziquantel.
Vegetables, salads and fruit should be thoroughly washed before consumption.
Cerebral hydatid disease:
Cerebral hydatid disease is very rare, representing only 2% of all cerebral
space occupying lesions even in the countries where the disease is endemic.
left parieto-occipital hydatid disease.
Orbital hydatid cyst.
Hydatid cysts rarely appear in the orbital cavity without
the involvement of the other organs. Most of them are
situated in the superolateral and superomedial angles of
the orbit. Inferiorly located cysts are very uncommon.
Hydatid disease of the lung.
The lung is the second most common site of involvement with
echinococcosis granulosus in adults after the liver (10-30% of
cases), and the most common site in children. The coexistence
of liver and lung disease is present in only 6% of patients
X-Ray chest PA, show calcified cyst at the lower or upper lung
Chest CT scan features include:
multiple or solitary cystic lesion (most common)
diameter of 1-20 cm
unilateral or bilateral
predominantly found in the lower lobes
Hydatid Disease of the liver.
Hydatid disease involves the liver in approximately 75% of cases
The right lobe is the most frequently involved portion of the liver.
Once in the human liver, cysts grow to 1 cm during the first
6 months and 2–3 cm annually thereafter, depending on
host tissue resistance.
X-Ray show hydatid disease of the right liver lobe.
Primary hydatid cyst of kidney.
Kidney involvement in echinococcosis is extremely rare, constituting
only 2-3% of all cases. Primary involvement of the kidney without
the involvement of the liver and lungs is even more rare.
Hydatid disease of adrenal gland.
Primary hydatid disease in the adrenal gland.
Hydatid cyst of the adrenal gland is rare; this entity is found in only 7% of all adrenal
cysts. It occurs in cases of disseminated infection by Echinococcus granulosus
beyond the hepatic and pulmonary filters. The infection is usually asymptomatic.
When symptoms are present, most are related to local visceral compression.
Pancreatic hydatid cyst with pancreatitis.
Primary hydatid cysts of the pancreas.
Pancreatic involvement by hydatid disease is uncommon. Establishing a precise diagnosis
may be difficult because the presenting symptoms and findings of investigations
may be similar to other more commonly encountered cystic lesions of the pancreas
Hydatid disease of the pancreatic body and tail.
Peritoneal hydatidosis can be primary or more frequently
secondary to hydatid cysts in the liver or rarely in the spleen.
Primary peritoneal hydatidosis is rare. The mechanism of
peritoneal infestation in such cases is not clear. Dissemination
via lymphatics or systemic circulation has been implicated as a
Secondary peritoneal hydatidosis almost always from hepatic
hydatid disease, and related to seeding from spontaneous
rupture of hepatic cyst into the peritoneum or spillage of cyst
fluid during surgery. In both instances, depending on the
patients immune response, this sudden release of hydatid
antigens into the peritoneal cavity can result in anaphlaxis. If
this does not occur, and viable organisms are present, then
multiple cysts can develop.
Peritoneal and hepatic hydatid disease with major duct obstruction.
Retro-vesical and seminal vesicle hydatid cyst.
Primary isolated echinococcal cyst of the seminal vesicle.
Bone hydatid disease.
Bone hydatid disease lacks a typical clinical appearance and image
characteristics on x ray or CT are similar to those of tuberculosis, metastases
and giant cell tumour or bone cysts. However, MRI does show distinctive
diagnostic features of bone hydatid disease, especially in the spine.