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Hydatid echinococcosis - Overview
Last reviewed: 04.07.2025
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Echinococcosis is a chronic biohelminthiasis caused by the parasitism of cestodes of the genus Echinococcus in humans.
ICD-10 codes
- B67. Echinococcosis.
- B67.8. Echinococcosis of liver, unspecified.
- B67.9. Echinococcosis of other organs and unspecified.
Hydatid echinococcosis (unilocular echinococcosis, cystic echinococcosis, Latin echinococcosis, English echinococcus disease) is a chronic zoonotic biohelminthiasis with a fecal-oral mechanism of transmission of the pathogen, characterized by the formation of parasitic cysts in the liver, less often in the lungs and other organs.
ICD-10 codes
- B67.0. Liver invasion caused by Echinococcus granulosus.
- B67.1 Echinococcus granulosus pulmonary invasion .
- B67.2 Bone invasion due to Echinococcus granulosus.
- B67.3. Invasion of other sites and multiple echinococcosis caused by Echinococcus granulosus.
- B67.4 Infestation due to Echinococcus granulosus, unspecified.
Epidemiology of hydatid echinococcosis
The source of E. granulosus for humans is most often domestic dogs, less often wild animals (wolves, jackals, etc.). The main transmission factor is hands contaminated with echinococcus oncospheres, which are found in abundance on the fur of infected dogs. Humans can also become infected when picking berries and herbs, drinking water from sources contaminated with helminth eggs. Hydatid echinococcosis is more common in certain professional groups: slaughterhouse workers, shepherds, tanners, hunters, their family members, especially children. There are different strains of echinococci adapted to different intermediate and final hosts. Some strains in humans, in particular the "horse strain" common in Western Europe and Great Britain, have a certain resistance, while the "sheep strain" is highly pathogenic for humans.
Hydatid echinococcosis is found on all continents. It is most often registered in countries with pasture cattle breeding, especially where dogs are traditionally used to protect sheep and cattle. In the southern hemisphere, the intensity of the lesion is especially high. In the CIS countries, echinococcosis is common in regions with developed livestock farming, mainly sheep farming: in the Caucasus, Kazakhstan and other countries of Central Asia, in Ukraine, and in Moldova.
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What causes hydatid echinococcosis?
Hydatid echinococcosis Echinococcus granulosus belongs to the type Plathelminthes, class Cestoda. family Taeniidae. Mature E. granulosus is a white tapeworm 3-5 mm long. It consists of a head with four suckers and a double crown of hooks, a neck and 2-6 segments. The last segment is filled with a uterus containing eggs (oncospheres), which have invasive ability and do not need to mature in the environment. Mature helminth parasitizes in the small intestine of the final host - carnivores (dogs, wolves, lynxes, cats, etc.). Mature segments enter the environment with feces. Eggs are highly resistant in the external environment, in winter they remain viable for up to 6 months.
Pathogenesis of hydatid echinococcosis
Due to the hematogenous route of spread, echinococcus oncospheres can be introduced into any organ, but most often echinococcal cysts are localized in the liver (30-75%) and lungs (15-20%), much less often in the central nervous system (2-3%), spleen, pancreas, heart, tubular bones and kidneys (up to 1%). The transformation of the oncosphere into a larva cyst in an infected person lasts about 5 months; during this time, it reaches a diameter of 5-20 mm. The pathological effect of echinococcus is due to mechanical and sensitizing factors. In most patients, a single organ is affected by one solitary cyst, but multiple echinococcosis can also develop.
Symptoms of hydatid echinococcosis
The following stages of hydatid echinococcosis are distinguished: preclinical, uncomplicated and the stage of complications.
In the most common lesion - echinococcosis of the liver - the first symptoms of hydatid echinococcosis usually appear several years or even decades after infection. Often, echinococcosis is diagnosed by chance (during routine fluorography, ultrasound) or during targeted examination of the population in foci. Hydatid echinococcosis is more often detected in middle-aged people. Symptoms of hydatid echinococcosis of the liver in uncomplicated cases: decreased performance, general weakness, dyspeptic disorders, headaches, sometimes allergic manifestations - skin rashes, itching, eosinophilia in the blood. The liver is enlarged, dense upon palpation (with the localization of the bladder deep in the parenchyma) or soft, elastic (with a superficial location of the cyst), with calcification - woody-dense.
How is hydatid echinococcosis diagnosed?
Symptoms (a tumor-like, slowly growing formation in the liver, lungs or other organs) and epidemiological data suggest echinococcosis.
Seroimmunological methods (ELISA, RIGA, RLA) give positive results in 90% of cases and more in case of liver damage, in case of pulmonary echinococcosis the efficiency is lower (60%). Antibody titers in the early period of invasion, in case of unopened or drug-untreated cysts may be low or reactions give negative results. Intradermal test with echinococcal antigen (known as Casoni reaction) is not used at present due to frequent development of allergic complications. Parasitological diagnostics is possible in case of breakthrough of echinococcal cysts into lumen of hollow organs - then scolexes or separate hooks of the parasite can be found in sputum, duodenal contents, feces.
How to examine?
How is hydatid echinococcosis treated?
The regimen and diet are determined by the nature of the complications.
Chemotherapy is performed in cases of cyst rupture, when there is a risk of seeding if the integrity of the cyst is compromised during surgery, as well as in cases of multiple small cysts (no more than 3-5 cm) of the liver, lungs and other organs, in which surgical intervention is technically difficult. Anti-relapse treatment of hydatid echinococcosis is recommended after surgery, when another localization of a small parasite cannot be ruled out.
How is hydatid echinococcosis prevented?
Hydatid echinococcosis can be prevented by maintaining personal hygiene. Particular vigilance is required when keeping dogs in the house and caring for animals. Planned deworming of dogs is carried out. In places unfavorable for echinococcosis, planned medical examination of risk groups is necessary.
What is the prognosis for hydatid echinococcosis?
After radical removal of echinococcal cysts, the prognosis is favorable; if surgical treatment is impossible, it is unfavorable.