Infectious Disease Compendium

Echinococcus

Microbi,ology

Tapeworms. E. canadensis, E. granulosus, E. multilocularis, E. vogeli. Echinococcus oligarthrus, Echinococcus shiquicus, Echinococcus equinus, Echinococcus ortleppi.

Epidemiologic Risks

Eating dog or other carnivore poop. Really. Dog poop carries the tapeworm and is on the food when you eat it. E. granulosis E. multilocularis: Sheep, goats, camels, and horses. World wide distribution.

E. canadensis is found in Alaska and N. Canada (PubMed); moose and elk most important intermediate hosts; dogs and wolves the definitive hosts.

Syndromes

Hydatid cyst disease, with liver involvement > lung > greater than other organs.

Most problems are due to mass action of the cysts; sudden rupture can lead to death from anaphylaxis. Percutaneous sampling of a cyst is probably much safer than a spontaneous rupture during a rugby game.

As a systematic review put it "Lethal anaphylaxis occurred in 0.03% of PT procedures, corresponding to 0.04% of treated cysts, while reversible allergic reactions complicated 1.7% of PTs, corresponding to 1.8% of treated echinococcal cysts. Analysis of the literature shows that lethal anaphylaxis related to percutaneous treatment of CE is an extremely rare event and is observed no more frequently than drug-related anaphylactic side effects."

Treatment

Asymptomatic cysts should be observed. If symptomatic, removal by someone who know what they are doing. Medical therapy (without drainage) includes albendazole (preferred) or mebendazole for prolonged periods; there are a variety of regimens. Probably not curative (about 50%).

Notes

Directions for removal of hydatid cysts, visualize the cyst, remove some fluid, and inject a cysticidal agent, hypertonic (30%) saline, iodophor, or 95% ethanol wait 30 minutes then remove all the fluid. This has been done under CT (preferred) as well as in the operating room.

It has been found in 8000 year old human remains.