Echinococcosis is a disease caused by larvae of the tapeworm genus Echinococcus. In Europe, the fox tapeworm, Echinococcus (E.) multilocularis, the causative agent of alveolar echinococcosis, and the dog tapeworm, E. granulosus, the causative agent of cystic echinococcosis, are found.
The fox tapeworm is mainly found in Austria, Germany, Switzerland, France and northern Italy. In Bavaria and North Tyrol it is found in every third to fourth fox on average, in Vorarlberg in almost every second fox. The United Kingdom, Norway, Finland, Malta and Ireland are officially free of the fox tapeworm. The dog tapeworm is found all over the world, with an increase in Eastern Europe, the Mediterranean area and the Balkan states. In Austria the dog tapeworm is considered to be extinct.
E. multilocularis: Intermediate host: small rodents; final host: fox
E. granulosus: Intermediate host: sheep, pig, cattle; final host: dog
Mode of transmission
Fox tapeworm: The 2-3 mm small segmented worms live in the small intestine of foxes, rarely of cats and dogs. Every one to two weeks they cut off the last tapeworm segment, which contains about 500 eggs, and release it into the environment with the faeces. If these tapeworm segments are taken up by suitable intermediate hosts (e.g. small rodents) during feeding, larvae develop from the eggs. Larvae reach the bloodstream via the intestinal mucosa and get into the organs, in particular the liver, where infectious tapeworm heads, so-called scolices, develop. Humans are an accidental host for these parasites. If a person ingests eggs, the larvae can develop and infiltrate the liver tissue like a malignant tumour, known as alveolar cysts. The clinical picture is known as alveolar echinococcosis.
Dog tapeworm: The 3-6 mm large adult worms live in the small intestine of dogs. Every one to two weeks they cut off the last tapeworm segment containing up to 1,500 eggs, which is released into the environment with the faeces. These tapeworm segments are taken up by intermediate hosts (sheep, goats, cattle, pigs) when grazing. Larvae develop from the eggs, which enter the bloodstream via the intestinal mucosa and continue on to the liver and other organs (e.g. lungs, heart, spleen), where they grow into vesicles, so-called fins, or cysts. Within these cysts, thousands of "heads" are formed from which new tapeworms can develop as soon as cyst-containing tissue is eaten by a dog. In humans, as in the intermediate hosts, the clinical picture is called cystic echinococcosis. Humans become infected via dirt and smear infection by ingesting Echinococcus eggs from fox or dog excrement.
Alveolar Echinococcosis: 5-15 years
Cystic Echinococcosis: months to years
Alveolar Echinococcosis: The most common symptoms are pain in the upper abdomen and jaundice, occasionally fatigue, weight loss or an enlarged liver caused by cancerous growth of the parasitic tissue.
Cystic echinococcosis: Frequent pain in the right upper abdomen due to encapsulated cysts in the liver up to 30 cm in size. The rarer infestation of the lungs is characterized by breathing difficulties and coughing.
Imaging procedures such as ultrasound, lung X-ray or computer tomography can show the differently structured, often calcified tissue changes. The suspected diagnosis is confirmed by specific antibody detection in the patient's blood, which also enables the differenciation between the species of E. granulosus and E. multilocularis. A negative serological result does not rule out the presence of a disease. The diagnosis can be made histologically from surgical material.
The aim of the treatment is the complete surgical removal of the Echinococcus cysts, which, however, is usually not or hardly possible at an advanced stage. Therefore, the treatment includes a combination of surgical intervention and administration of an antihelminthic chemotherapy.
Cystic echinococcosis: For therapy, the PAIR technique is also available: ultrasound-guided puncture (P), aspiration (A), instillation (I) of wormhead killing substances and reaspiration (R) of the cyst contents, together with antihelminthic therapy.
Echinococcus eggs have a relatively high resistance to cold and can therefore remain infectious for many months. However, dryness and high temperatures kill them within a short time. To avoid infection with E. multilocularis, hands should be washed thoroughly after contact with foxes or fox fur. To avoid infection with E. granulosus, dogs should be dewormed regularly and not fed with slaughterhouse waste from infected sheep.