Echinococcosis, often called hydatid disease, is a serious human cestode infection that is found in most areas of the world. A larval stage of Echinococcus granulosus tapeworms causes cystic hydatid disease in places where dogs eat entrails of herd animals, most notably in Africa, Asia, the Middle East, Europe, South America, and parts of North America. E. multilocularis causes human alveolar hydatid disease and is identified mostly in Asia and Europe. Far from being relegated to the annals of history or remote recollections of our training years, echinococcosis still is an active problem on every continent except Antarctica.
Who Cares About Echinococcosis?
Parasitologists care. During recent months, Advances in Parasitology has published 10 articles totaling 932 pages reviewing current knowledge about echinococcosis. In addition to the paper by Kern and colleagues highlighted here, other papers deal with the history, biology, ecology, epidemiology, immunology, and control of echinococcosis.
Patients and families care. Measuring the loss of productive years of life due to an illness as Disability Associated Life Years (DALYs), echinococcosis accounts for more than 1.5 million DALYs each year. This is similar to the extent of the effect of onchocerciasis, dengue, and Chagas disease.
Policy makers and economists care. Accounting for direct and indirect costs of human hydatid disease, as well as livestock-associated costs of disease, it is estimated that echinococcosis costs approximately $2.2 billion each year.
What’s New? What Should Infectious Disease Clinicians Know About Echinococcosis?
Epidemiology. Since some of us started training, two newer “neotropical” forms of echinococcosis have been recognized and characterized. Identified in the 1970s and now occurring in some parts of Latin America, E. vogeli causes a form of neotropical echinococcosis with multiple cysts. Recognized even more recently, E. oligarthrus is emerging as a cause of unicystic neotropical echinococcosis in rural parts of Central and South America; however, only four human cases have been reported to date.
Clinical Presentation. E. granulosus parasites often are acquired in childhood but require many years of cystic growth to become symptomatic. The lung is a common site of infection in children, but two-thirds of adult infections occur in the liver. Bone, renal, splenic, and brain lesions are seen less commonly. Cardiac cysts have been reported in the ventricular wall. E. multilocularis rarely presents during childhood and almost always is found in the liver. Rather than being confined to cysts, these alveolar lesions bud and invade the liver in ways that mimic malignant tumors. Liver cysts can present as notable abdominal masses or with obstructive jaundice. Meanwhile, pulmonary lesions can produce pain, cough, and hemoptysis. As known in the past, cyst rupture from accidental or surgical trauma can lead to anaphylaxis or hypersensitivity pneumonitis.
Diagnosis. The World Health Organization has disseminated and validated a classification system for the diagnosis of various forms of cystic echinococcosis based on ultrasound findings. This grading system relates to the complexity of cysts and to the activity of the infecting larvae. Alveolar lesions are graded similarly by a World Health Organization system based on the location and extension of liver lesions, the involvement of neighboring nodes and organs, and the presence of distant metastatic lesions. Computed tomography and magnetic resonance imaging can provide helpful details about alveolar lesions that are not discernable on ultrasound. Sensitive serologic tests can help rule out disease, and specific serologic tests can help confirm disease. Parasites sometimes can be retrieved from cystic lesions.
Management. The treatment of patients with cystic disease is guided by stage and location. Albendazole alone can result in cure of some small cysts, but several months of treatment may be required. Larger lesions can be treated with percutaneous aspiration, instillation of scolicidal agents, and re-aspiration; nonetheless, albendazole usually is given before and after this procedural treatment. Complex cysts should be removed surgically, again with coverage with albendazole. Alveolar disease often requires radical surgery involving removal of parts of the liver or actual transplantation along with two years of post-operative albendazole. Albendazole now is available in most areas of the world and is absorbed best when taken with a fatty meal.
For future reading:
Cabada M, et al. Echinococcosis. Chapter 330. In: Kleigman RM, St. Geme JW, eds. Nelson Textbook of Pediatrics, 21st ed. In press; 2017.
Echinococcosis continues to cause significant disease in much of the world, and a new form is emerging in Latin America. Combinations of medical, procedural, and surgical treatment usually are effective, but long-term albendazole may be required.
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