Those Dog-Gone Cysts

A Case Study about Echinococcus granulosus by Sarah Wycoff

Patient History

53-year-old Middle-Eastern female

Presented to the hospital Prompt Care Clinic with a severe cough and chest pains

Surgeon at another hospital had removed a cyst from her lungs and liver

Questions to Consider

What caused the cysts that were removed?

How is this parasite transmitted to humans?

How does the lab help in the diagnosis of this parasite?

What is the treatment for this parasite?

Echinococcus Species

3 known species of Echinococcus are medically important Echinococcus granulosus Echinococcus multiocularis Echinococcus vogeli

Echinococcus granulosus

A zoonotic infestation by a tapeworm causing hydatid disease

Very rare disease in the continental US (less than 1 case per 1 million inhabitants)

Endemic areas include Mediterranean counties, the Middle East, Iceland, Australia, New Zealand

Life Cycle

Dogs are the definitive hosts Adult worm develops in the small intestine Eggs are voided in the feces of the dogs

Sheep are intermediate hosts

Humans are accidental intermediate hosts Larval form develops mainly in the liver and lungs

The cycle is completed when a dog eats a cyst-infested liver or lungs.

Life Cycle

Infected Dogs

F. Rochette, 1999, Dog Parasites and Their Control, Janssen Animal Health, B.V.B.A.

Small intestine of a dog infected with Echinococcus granulosus

 Adult tapeworms are small (2 mm) but they can be very numerous

Adult Tapeworm

Body is separated into 3 sections

Scolex with nonretractable rostellum armed with double crown of 28-50 hooks

Infective stage: Egg

Found in dog feces Resembles Taenia

eggs

Metacestode (cyst)

UnilocularSub spherical in shapeFluid-filledPulmonary cyst are commonly found in the lower lobe on the right side

http://www.biosci.ohio-state.edu/~parasite/echinococcus.html

Human Host

Each egg contains an embryo (oncosphere)

Eggs hatch in the human stomach and release the oncosphere

The oncosphere penetrate the intestinal lining and enter the blood stream

Travel to any organ, usually lung and liver, and a cyst develops

Cyst stage in Humans

A single protoscolex.“Hooks” can be seen that will form the hooks associated with the adult

worm's rostellum

The cyst consists of a thick outer layer (*), several thinner internal layers, and many protoscolices.

The protoscolices are often called "hydatid sand."

http://www.biosci.ohio-state.edu/~parasite/echinococcus.html

Symptoms

Vary by size and site of cyst

Usually no symptoms until cyst becomes enlarged

Liver: jaundice, portal hypertension, pain

Lung: coughing, shortness of breath, chest pain

Brain: seizures, paralysis

Rupture of cyst: anaphylactic shock, spread of scolices, death

Diagnosis

Radiographic images of lungs and liverExamination of sputum or bronchial washes Protoscolices Membranes Hooklets

Serologic test Increase sensitivity if liver and lungs are

infected

Morbidity

Free rupture of echinococcal cyst (with or without anaphylaxis)Infection of the cystDysfunction of the affected organs Biliary obstruction Cirrhosis Bronchial obstruction Renal outflow obstruction

Treatment

Surgery Risks of operative morbidity, recurrence of

cyst, anaphylaxis or dissemination of the infection

Drugs Albendazole, mebendazole or praziquantal

Summary

Patient has hydatid disease caused by Echinococcus granulosusPatient continuing with oral treatments of albendazole Patient is seen every 3 months by her physicianPeriodic CT scans are performed on her chest and liver

References

Dandan, Imad MD. “Hydatid Cyst” November 22, 2002. http://www.emedicine.com/med/topic1046.htm

Brunetti, Enrico MD. “Cystic Echinococcosis” March 5, 2004

http://www.emedicine.com/med/topic629.htm

http://www.biosci.ohiostate.edu/~parasite/echinococcus.html

Credits

This case study was prepared by

Sarah Wycoff, MT(ASCP) while she was a

Medical Technology student in the

2004 Medical Technology Class at

William Beaumont Hospital inRoyal Oak, MI.