Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 35-19: Invasive Cestode Infections + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ History of exposure to dogs or wild canines in an endemic area Large cystic lesions, most commonly of the liver or lung Positive serologic tests +++ General Considerations ++ The principal species that infect humans Echinococcus granulosus, which causes cystic hydatid disease Echinococcus multilocularis, which causes alveolar hydatid disease Infection occurs when humans are intermediate hosts for canine tapeworms Transmitted by ingesting food contaminated with canine feces containing parasite eggs Eggs hatch in intestines to form oncospheres, which Penetrate the mucosa Enter the circulation Encyst in specific organs as hydatid cysts E granulosus forms cysts most commonly in the liver (65%) and in the lungs (25%) However, cysts may develop in any organ, including Brain Bones Skeletal muscles Kidneys Spleen Cysts are most commonly single and can persist and grow slowly for many years +++ Demographics ++ E granulosus Transmitted by domestic dogs in areas with livestock (sheep, goats, camels, and horses) as intermediate hosts Endemic in Africa, the Middle East, southern Europe, South America, central Asia, Australia, New Zealand, and the southwestern United States E multilocularis Causes human disease much less commonly Transmitted by wild canines Endemic in northern forest areas of the northern hemisphere, including central Europe, Siberia, northern Japan, northwestern Canada, and western Alaska An increase in the fox population in Europe has been associated with an increase in human cases Other species that cause limited disease in humans are endemic in South America and China + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Infections are commonly asymptomatic Infections may be noted incidentally on imaging studies or present with symptoms caused by an enlarging or superinfected mass Findings may include Abdominal or chest pain Biliary obstruction Cholangitis Portal hypertension Cirrhosis Bronchial obstruction leading to segmental lung collapse Abscesses Cyst leakage or rupture may be accompanied by a severe allergic reaction, including fever and hypotension Seeding of cysts after rupture may extend the infection to new areas E multilocularis generally causes a more aggressive disease than E granulosus, with initial infection of the liver, but then local and distant spread commonly suggests a malignancy Obstructive findings in the liver and elsewhere develop with chronic infection +++ Differential Diagnosis ++ Amebic or pyogenic liver abscess Malignant or benign tumor of liver or other involved organ Fascioliasis (sheep liver fluke) Clonorchiasis (Chinese liver fluke) Choledocholithiasis Congenital liver cyst or liver cyst associated with polycystic kidney disease Cavitary pulmonary tuberculosis Cysticercosis + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Serologic tests Include ELISA and immunoblot Offer sensitivity and specificity over 80% for E granulosus liver infections, but lower sensitivity for involvement of other organs Serology is somewhat more reliable for E multilocularis infections May also distinguish the two major echinococcal infections +++ Imaging Studies ++ Diagnosis usually based on imaging studies Ultrasonography CT MRI In E granulosus infection, a large cyst containing multiple daughter cysts that fill the cyst interior is highly suggestive of diagnosis In E multilocularis infection, imaging shows an irregular mass often with areas of calcification + Treatment Download Section PDF Listen +++ +++ Medications ++ Albendazole Often used in conjunction with surgery When used alone, 10–15 mg/kg/day orally has shown efficacy, with courses of 3 months or longer; alternating cycles of treatment and rest may be needed Mebendazole (40–50 mg/kg/day orally) is an alternative Praziquantel may also be effective In some cases, medical therapy is begun, with surgery performed if disease persists after some months of therapy +++ Surgery ++ Treatment of cystic hydatid disease Involves cautious surgical resection of cysts, with care not to rupture cysts during removal Injection of a cysticidal agent is used to limit spread in the case of rupture Treatment of alveolar cyst disease Generally relies on wide surgical resection of lesions Therapy with albendazole before or during surgery may be beneficial and may also provide improvement or even cure in inoperable cases +++ Therapeutic Procedures ++ Percutaneous aspiration, injection, and reaspiration (PAIR) Can be used when cysts are inoperable Patients receive antihelminthic therapy Cyst is partially aspirated Scolicidal agent (95% ethanol, hypertonic saline, or 0.5% cetrimide) injected after diagnostic confirmation Risk of anaphylaxis is small; has been reported in about 2% of procedures, but death due to anaphylaxis has been rare Do not use PAIR if cysts communicate with biliary tract + Outcome Download Section PDF Listen +++ +++ Follow-Up ++ Liver chemistry tests and complete blood counts should be monitored weekly when using albendazole +++ Prognosis ++ About 15% of untreated patients eventually die because of the disease or its complications 90% of patients with nonresectable masses die within 10 years 25% recurrence rates after surgery +++ Prevention ++ In endemic areas, prevention is by prophylactic treatment of pet dogs with 5 mg/kg of praziquantel at monthly intervals to remove adult tapeworms and by health education to prevent feeding of offal to dogs +++ When to Refer ++ All patients +++ When to Admit ++ Patients with symptomatic cysts Patients who will have percutaneous aspiration of cysts or surgery + References Download Section PDF Listen +++ + +Bhutani N et al. Hepatic echinococcosis: a review. Ann Med Surg (Lond). 2018 Nov 2;36:99–105. [PubMed: 30450204] + +Kikuchi T et al. Human proliferative sparganosis update. Parasitol Int. 2019 Dec 10:102036. [PubMed: 31841658] + +Meinel TR et al. Vertebral alveolar echinococcosis—a case report, systematic analysis, and review of the literature. Lancet Infect Dis. 2018 Mar;18(3):e87–98. [PubMed: 28807628] + +Wen H et al. Echinococcosis: advances in the 21st century. Clin Microbiol Rev. 2019 Feb 13;32(2):e00075–18. [PubMed: 30760475]