Pulmonary Echinococcus Megan Brundrett December 15, 2009

Pathology 1

Pathology 2

Echinococcus Cestodes – divide their life cycle in 2 or more hosts Intermediate host – immature parasite as a tissue cyst Definitive host – mature parasite as a tapeworm Echinococcus granulosus Echinococcus multilocularis

E. granulosus Hydatid disease Definitive hosts are dogs or other canines Intermediate hosts – sheep, goats, camels, horses, humans Australia, New Zealand, Argentina, Chile, Ireland, Scotland, middle Europe, Kenya

E. multilocularis Alveolar disease Definitive host – foxes, and other canines Intermediate host – rodents, humans Arctic areas of United States, Canada, and Russia

Life Cycle (1) Adult tapeworms in bowels of definitive host (2) Eggs passed in feces, ingested by intermediate host (3) Onchosphere penetrates intestinal wall, carried via blood vessels to lodge in organs (4) Hydatid cysts develop (5) Protoscolices (larvae) ingested by definitive host (6) Attach to small intestine of definitive host and grow to adult worm.

Hydatid disease E. granulosus 75% hepatic involvement, 25% pulmonary Other organs – brain, bone, heart, kidney Cause symptoms with mass effect, rupture, secondary infection

Alveolar disease E. multilocularis < 5% of symptomatic Echinococcal infections Lacks a limiting membrane like hydatid disease and causes more infiltration to surrounding tissues. Clinical presentation – jaundice, RUQ pain, malaise If untreated >90% die within 10 years Now prognosis improved b/c of albendazole therapy. Very difficult to surgically resect.

Pulmonary Echinococcal Diease 60% right lung 50-60% in lower lobes Lungs may be a more common site in children 30% have multiple cysts in the lungs 20% of pts with lung involvement have liver involvement

Clinical Manifestations Unruptured cyst: Chest pain, hemoptysis, chronic cough Ruptured cyst: Cough, fever, expectorating salty material (hydatid membrane and larvae). Acute hypersensitivity with rupture: Fever, urticaria, sometimes anaphylaxis Superinfection by bacteria, fungal presenting with fever, sepsis Pulmonary HTN, Pulmonary embolism

Diagnosis CXR: Round or oval mass with smooth borders. No calcifications. If pericyst (fibrous capsule that host makes) incorporates bronchioles, than air penetrates between the pericyst and exocyst creating a meniscus sign or crescent shape. CT scan: Thin enhancing ring if cyst is intact. Fluid filled in center. Homogenous.

CXR

Differential Diagnosis Primary lung cancer Metastatic cancer Tuberculosis Bronchogenic Cyst Round pneumonia Aspergillosis

Laboratory Data Less than 15% have peripheral eosinophilia, only if leakage of antigenic material Immunodiagnostic testing for serum antibodies: + 50% for pulmonary, > 90% for hepatic - False positive if have another parasitic infection - More likely to have false negative if intact cyst Percutaneous aspiration: Not often use in pulmonary echinococcus, but used with hepatic cysts for diagnosis and treatment. Fluid contains hooklets, protoscolices, etc.

Management Surgical resection: Treatment of choice Minimize spilling of contents to prevent spread, and allergic reaction Intact cyst Cystic fluid aspiration, and scolicidal solution (hypertonic saline) for deactivation Recurrance rate after removal 1-3%

Management 2 Chemotherapy: Used with poor surgical candidate, unresectable lesion, multiple cysts, after cyst rupture, or if intraoperative spillage Prior to surgery reduces tension of cyst Albendazole 400 mg PO BID Length of treatment 3-6 months No established monitoring guidelines for response of therapy Disappearance of cysts in 30%, decrease in size in 30-50%, no change in 20% 25% relapse rate, more common with multiple cysts, children and elderly adults

Prevention Avoiding close contacts with dogs Careful washing of hands, and produce Prohibition of home slaughter of sheep and to prevent dogs from eating the infected viscera Treating infected dogs with Praziquantal Eliminating stray dogs Vaccination: Appears to be 95% effective in animal studies, not used on humans currently

References “Clinical manifestations and diagnosis of cystic and alveolar echinococcosis.” UptoDate. 2009.<www.uptodate.com> Goldman, Lee et al. Cecil Textbook of Medicine. Philadephia: Saunders, 2004. Morar,R and Feldman,C. Eur Respir J 2003; 21: 1069-1077. “Treatment and prevention of echinococcus.” UptoDate. 2009.<www.uptodate.com>