Cystic echinococcosis; echinococcus granulosus infection E67.5

E. granulosus, the small dog tapeworm, is a 0.4-0.7 cm long tapeworm (Cestoda) with a hook-studded scolex, typically consisting of 3 (2-6) limbs (proglottids). These contain a uterus with lateral sacs which, when mature, can hold up to 1,500 eggs. The egg-filled mature end members detach from the worm and are excreted with the faeces. After oral uptake of the eggs by the intermediate host, larvae are formed, which usually reach the liver by haematogenesis, but also the lungs and very rarely other organs, where they remain. A cyst (hydatide), which is delimited by a connective tissue capsule, forms and can reach a diameter of several decimetres. The cyst wall consists of several layers - an outer layer of connective tissue formed by the host, a laminated membrane (cuticle) and a germ layer. The germinal layer develops into buds (brood capsules) in which protoscolices (head units) develop.

E. granulosus is distributed worldwide. In Europe it is mainly found in the Mediterranean countries and the Balkans, where sheep farming is of great importance. In Germany, infections hardly occur any more. The vast majority of the diseases probably occur in migrants who have become infected in their countries of origin. Infections from imported dogs are also possible. Diseases from tourists who have become infected while travelling in endemic areas are a rarity.

The main host of E. granulosus is the dog, rarely the cat. After eating raw larval offal, adult tapeworms develop in dogs. Ruminants (especially sheep and cattle) serve as intermediate hosts. They take up the eggs while grazing on contaminated pastures. In Poland, the pig has been identified as the intermediate host for E. granulosus. Humans can be infected as a false host with the larval stage.

Possible transmission routes of the parasite via the eggs excreted with the faeces of the main host are direct contact (fur of the main host), smear infections, handling of contaminated soil or ingestion of contaminated food. The risk of infection is particularly high in high-demic areas where close contact with the main host (dog) exists under poor hygienic conditions. The larvae hatch in the intestine and reach the liver via the portal vein and from there other organs such as the lungs.

The incubation period is variable and can range from several months to many (10-20 years) years.

A contagiousness from person to person does not exist. Operation material is not infectious.

All age groups are affected by cystic echinococcosis, including infants, children and adolescents.

Variable clinical course. It depends on the location of the cysts, their size and inflammatory host response. The clinical picture is characterized by slowly growing cysts (especially in the liver and lungs), which may remain asymptomatic for several years and only become symptomatic by space-occupying, secondary bacterial infection of the cysts, cystobiliary or -bronchial fistulas or anaphylactic reactions after rupture of the cysts. In most patients only one organ is affected.

The most frequent cysts are those of the liver (70%) and lungs (20%). Larger liver cysts can be palpated as resistance in the right upper abdomen. Abdominal pain is often the first symptom. The compression of bile ducts and the transfer of cyst contents via cystobiliary fistulas into the bile ducts lead to obstruction of the bile ducts, possibly accompanied by cholangitis. Discharge of hydatid fluid from a cyst can lead from mild allergic reactions to anaphylactic shock.

Secondary echinococcosis can be caused, for example, by the discharge of hydatid fluid into the pleural or peritoneal cavity. The clinical symptoms of rare cyst localizations (including cerebral, spinal, cardiac and osseous) are organ-related and diverse.

Remissions without therapy are frequently observed and show the benignity of this disease as long as none of the above mentioned risk constellations are present.

IHA, ELISA, IFT and Western Blot for the detection of antibodies (see below Echinococcus Spp.). The serological differentiation of E. granulosus and E. multilocularis is possible with specific bands in the Western Blot and in a specific ELISA test. A negative result of the serology does not exclude a disease.

The diagnosis can be made histologically from surgical material and microscopically from puncture material (protoscolices, hooks). Diagnostic punctures can only be performed under consideration of special precautions (see also Therapy).

In the early stages of the disease it is very difficult to diagnose. Diagnosis mainly by means of imaging techniques (sonography, CT, MRT). Ultrasound-based stage classification is an extremely helpful tool for diagnosis, therapy decisions and assessment of the course of the disease. Serology (see below Echinococcal Serology)

Dysontogenetic cysts, benign and malignant tumours, abscesses, tuberculosis, alveolar echinococcosis.

Treatment in designated centres is recommended. There are several therapeutic options, depending on the clinical picture and stage of the cyst:

Internal therapy:

• Watch-and-wait strategy for inactive cysts that do not cause functional problems.
• Treatment with albendazole alone (with accompanying check-ups).

Operative therapy:

• In the most frequent manifestation, the liver cysts by endocystectomy and omentoplasty or with resecting procedures. Perioperatively, treatment is with albendazole.
• Puncture-Aspiration-Injection-Reaspiration (PAIR), whereby the injection of the sterilising substance (95% alcohol) is only carried out after the reliable exclusion of cystobiliary fistulas (see above). Periinterventional treatment is carried out with albendazole.

According to § 7 para. 3 IfSG, the RKI is not notified by name of the direct or indirect detection of Echinococcus sp. The reports must be submitted to the RKI no later than 2 weeks after they have been received.