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Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Cestodes

Echino Coccosis : Clinical Aspects

The enlarging E. granulosis cysts produce tissue damage by mechanical means. The clinical presentation depends on their number, site, and rate of growth.



The enlarging E. granulosis cysts produce tissue damage by mechanical means. The clinical presentation depends on their number, site, and rate of growth. Typically, there is a latent period of 5 to 20 years between acquisition of infection and subsequent diagnosis. Intervals as long as 75 years have been reported occasionally.

In sylvatic infections, two thirds of the cysts are found in the lung, the remainder in the liver. Most patients are asymptomatic when the lesion is discovered on routine chest x-ray or physical examination. Occasionally, the patient may present with hemoptysis, pain in the right upper quadrant of the abdomen, or a tender hepatic mass. Significant morbidity is uncommon, and death extremely rare. In the pastoral form of disease, 60% of the cysts are found in the liver, 25% in the lung. One fifth of all patients show involve-ment of multiple sites. The hydatid cysts, which grow more rapidly (0.25 to 1 cm/year) than the sylvatic lesions, may reach enormous size. Twenty percent eventually rupture, in-ducing fever, pruritus, urticaria, and, at times, anaphylactic shock and death. Release of thousands of scolices may lead to dissemination of the infection. Rupture of pulmonary lesions also induces cough, chest pain, and hemoptysis. Liver cysts may break through the diaphragm or rupture into the bile duct or peritoneal cavity. The majority, however, present as a tender, palpable hepatic mass. Intrabiliary extrusion of calcified cysts may mimic the signs of acute cholecystitis; complete obstruction results in jaundice. Bone cysts produce pathologic fractures, whereas lesions in the CNS are often manifest as blindness or epilepsy. Cardiac lesions have been associated with conduction disturbances, ventricular rupture, and embolic metastases. It has been suggested that circulating antigen – antibody complexes may be deposited in the kidney, initiating membranous glomerulonephritis.


In E. granulosis – infected patients, chest x-rays reveal pulmonary lesions as slightly ir-regular, round masses of uniform density devoid of calcification. In contrast, more than one half of hepatic lesions display a smooth, calcific rim. CT, ultrasonography, and MRI may reveal either a simple fluid-filled cyst or daughter cysts with hydatid sand. Endo-scopic retrograde cholangiography has been valuable for determining cyst location and possible communication with the biliary tree. Because of the potential for an anaphylac-toid reaction and dissemination of infection, diagnostic aspiration has been considered contraindicated. Nevertheless, in the hands of some investigators, ultrasonically guided percutaneous drainage, followed by the introduction of ethanol to kill protoscoleces and germinal layer, has proven to be safe and useful, both diagnostically and therapeuti-cally . In patients with ruptured pulmonary cysts, scolices may be demon-strated in the sputum.

In most cases, confirmation of the diagnosis requires serologic testing. Unfortunately, current procedures are not totally satisfactory. Indirect hemagglutination and latex agglu-tination tests are positive in 90% of patients with hepatic lesions and 60% of those with pulmonary hydatid cysts. When using hydatid cyst fluid or soluble scolex antigen, the presence of a precipitin line in the immunoelectrophoresis test appears to be more spe-cific. An adaption of this test to an enzyme-linked immunoelectrodiffusion technique ap-pears to provide a rapid, sensitive diagnostic test. Other serologic tests are in the process of evaluation. Polymerase chain reaction assay has been shown capable of detecting picogram quantities of Echinococcus genomic DNA in fine-needle biopsy material from patients with suspected echinococcosis.


For years, the only definitive therapy available was surgical extirpation. Patients with pulmonary hydatid cysts of the sylvatic type and small calcified hepatic lesions underwent surgery only when they became symptomatic or the cysts increased dramatically in size over time. For other lesions, Percutaneous Aspiration, Infusion of scolicidal and Reaspiration (PAIR) can be utilized in lieu of surgery. Presently, it is recommended that highdose albendazole be administered prior to, and for several weeks (or years in the case of E. multilocularis infection) after surgery and/or aspiration. Infected dogs should be wormed, and infected carcasses and offal burned or buried. Hands should be carefully washed after contact with potentially infected dogs.

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