Alveolar echinococcosisB67.5

Echinococcosis caused by E. multilocularis, a parasite only found in the northern hemisphere. In Europe, E. multilocularis is endemic in an area that includes southern Germany (Baden-Württemberg, Bavaria), northern Switzerland, western Austria and eastern France.

The adult E. multilocularis is a 0.2-0.4 cm long tapeworm (Cestoda), which typically has 5 (2-6) limbs (proglottids) and has a sac-shaped uterus containing about 200 eggs. Intermediate and false hosts become infected by oral ingestion of the eggs. Almost always only the liver is affected by the larvae. In contrast to E. granulosus, however, no closed cyst is formed; instead, infiltrative growth of the larvae occurs, comparable to the growth of a malignant tumour. The germinal epithelium forms sprouts that penetrate the liver tissue. In the natural intermediate host, numerous protoscolices (head structures) are formed; in humans (false host) this occurs only in exceptional cases.

Occurrence: E. multilocularis is only distributed in the northern hemisphere (southern Germany, northern Switzerland, western Austria and eastern France). Most of the cases reported in Germany come from rural areas of the southern federal states, but some cases have also been reported from other federal states. As a consequence of the increasing colonisation of cities and inhabited areas by foxes, but also by infections in dogs or cats, eggs of the small fox tapeworm can also enter the urban environment of humans, also endemic in northern China and Siberia, northern Japan (Hokkaido), western Austria and eastern France.) The majority of cases reported in Germany come from rural regions of the southern federal states, but some cases have also been reported from other federal states. As a consequence of the increasing colonisation of cities and inhabited areas by foxes, but also by infections in dogs or cats, eggs of the small fox tapeworm can also enter the urban environment of humans.

E. multilocularis is distributed only in the northern hemisphere (southern Germany, northern Switzerland, reservoir main end host for E. multilocularis is the fox. Infections in dogs are possible, cats seem to be of minor importance as hosts.

The larval stage (metazestode) infects rodents as intermediate hosts (e.g. field mice, voles, muskrats) or humans as a false host. The infection of the final hosts occurs through the consumption of infected rodents. However, human infection through contact with infected rodents is not possible.

Route of infection: Humans ingest the worm eggs through contaminated hands either after direct contact with infected end hosts (fox, dog, cat), to whose fur the eggs may adhere, or by handling contaminated soil. The possibility of transmission through contaminated food (wild berries, mushrooms) or contaminated water has not been clarified.

Incubation period: The incubation period is not known, but is assumed to be 10-15 years.

Infectiousness: An infectiousness from person to person does not exist. Operation material is not infectious.

The average age of the disease is between 50 and 60 years. Diseases in children and adolescents are very rare and have mainly been observed in immunodeficiency.

Variable clinical course is typical. After the peroral uptake of eggs, an infection of the liver occurs, usually unnoticed for many years. The larva proliferates in the liver tissue and forms an alveolar tumour. Mostly unspecific upper abdominal pain. Affected organ area can decay necrotically. Pseudocysts are formed (no formation of cyst capsules - in contrast to the dog tapeworm! The compression of important organs leads to a number of complications: cholestasis, portal hypertension, liver cirrhosis. Infiltrative growth or lymphogenic or haematogenic spread can lead to an infestation of other organs (peritoneum, lungs, brain).

Serological methods for the detection of antibodies (ELISA, IHA, Western Blot) are available (see also Echinococcus Spp). When using Echinococcus raw antigen, Echinococcosis can be detected in ELISA procedures with a sensitivity of approx. 95%. It is difficult to differentiate between cystic and alveolar echinococcosis using serological methods. However, with high antibody titers, a specificity of 80-90% can be achieved using recombinant antigens.

Imaging procedures (especially ultrasound); furthermore CT and MRT; serology, detection of parasites from surgical material.

Liver cell carcinoma; cystic echinococcosis. Otherwise depending on organ symptoms (DD: cholestasis, portal hypertension, liver cirrhosis)

Treatment in designated centres is recommended. Many patients are no longer radically operable at the time of diagnosis. Drug therapy with benzimidazoles (mebendazole, albendazole) is therefore the therapy of choice and is used for life in these inoperable cases. In the case of curatively resorbable findings, therapy with benzimidazoles is administered for 2 years.

Overall, the course of the disease shows a steady progression. Untreated, the disease leads to death.

1. Deplazes P et al (2004) Wilderness in the city: the urbanization of Echinococcus multilocularis. Trends Parasitol 20: 77-84
2. Hosch W et al (2003) Cystic Echinococcosis: The key role of imaging techniques in diagnosis and therapy. Progress Röntgenstr 176: 679-687
3. Kern P (2003) Echinococcus granulosis infection: clinical presentation, medical treatment and outcome. Langenbeck's Arch Surg 388: 413-420
4. Kern P et al (2004) Risk Factors for Alveolar Echinococcosis in Humans. Emerg Inf Dis 10: 2088-2093
5. RKI: Zoonoses. Annual report 2005 Epid Bull 2005; 28: 237-238