Echinococcosis is a parasitic disease caused by infection with tiny tapeworms of the genus Echinocococcus. The infection behaves as a slow-growing malignant tumor. Initially, it is located in the liver and then may spread to any other organ through metastases. Without appropriate therapeutic management, the infection is lethal.
The infection behaves as a slow-growing malignant tumor. Initially, it is located in the liver and then may spread to any other organ through metastases. Without appropriate therapeutic management, the infection is lethal. A number of herbivorous and omnivorous animals act as intermediate hosts of echinococcus. This means they get infected by ingesting the parasite eggs in the contaminated ground and develop parasitic larval stages in their viscera.
Human infection with E. granulosus leads to the development of one or more hydatids located mainly in the liver and lungs, and less frequently in the bones, kidneys, spleen, muscles, central nervous system and eyes. The asymptomatic incubation period of the disease can last many years until hydatid cysts grow to an extent that triggers clinical signs. Non-specific signs include anorexia, weight loss and weakness. Other signs depend on the location of the hydatid(s) and the pressure exerted on the surrounding tissues. Abdominal pain, nausea and vomiting are commonly seen when hydatids occur in the liver. If the lung is affected, clinical signs include chronic cough, chest pain and shortness of breath.
Alveolar echinococcosis is characterized by an asymptomatic incubation period of 5–15 years and the slow development of a primary tumour-like lesion which is usually located in the liver. Clinical signs include weight loss, abdominal pain, general malaise and signs of hepatic failure. Alveolar echinococcosis occurs only in the northern hemisphere, in geographically limited foci (endemic areas) of west-central Europe, Turkey, most areas of the former Soviet Union, Iran, Iraq, western and central China, and northern Japan (Hokkaido Island). The survival rate at 5 years in untreated patients averages 40%. Therapeutic approaches that have been developed since the early 1980s have markedly improved the prognosis of the disease. The actuarial survival rate at 5 years was 88% in a series of 80 patients observed from 1983-1993. The typical age at onset is 55 years. In endemic areas in Europe, the male-to-female ratio is approximately equal.
The basic medical treatment is chemotherapy with benzimidazoles (eg, mebendazole, albendazole) at high doses. For simple cases of cystic echinococcosis, the most common form of treatment is open surgical removal of the cysts combined with chemotherapy using albendazole and/or mebendazole before and after surgery. For alveolar echinococcosis, surgical removal of cysts combined with chemotherapy for up to two years after surgery is the only sure way to completely cure the disease.