Echinococcus

(Hydatid Disease-Tapeworms of Concern)  Echinococcosis is a disease of people and animals caused by one of three tiny tapeworms.  Each of the three species differs in regard to animal hosts (the animal that can pass the eggs in a stool), the general geographic areas they are most prevalent in, and signs of the disease they cause. The three species are Echinococcus multilocularis, E. granulosus, and E. vogeli.  The disease may be serious to fatal in people but can be prevented. E. multilocularis is very short (about 1/8 inch), making it very difficult to see in the stools.  It may be contracted from cat or dog feces. The eggs of the parasite resemble the eggs of the more common tapeworm, making diagnosis by routine testing difficult.  This tapeworm is apparently becoming more prevalent in the mid-central states and in Canada.  It takes two different animals for the worm to complete its life cycle.

The adult worm stage of E. multilocularis lives in the intestines of foxes, coyotes, dogs, and cats.  These animals pass the tapeworm or its segment in their stool, and the eggs are spread throughout the soil.  The eggs can live for months outside on the ground.  A rodent, sheep, or person becomes infected by accidentally swallowing the eggs.  The eggs hatch in the intestine and migrate via the bloodstream or lymph into the liver, lungs, or brain.  There they develop into large cysts that resemble cancerous growths.  The cysts remain in the rodent until they are eaten by a dog, coyote, fox, or cat, and then the cycle starts over again.  People can become very ill with large cysts, and in some cases death may result.

E. granulosus is similar except it is more widespread throughout the world, and the domestic dog is, for example, the main host.  Contaminated feces are eaten by sheep as they graze, and the cystic stage develops over a 3-year period in the sheep.  If an infected sheep is killed and eaten by domestic or wild dogs, the life cycle becomes complete.  If a person accidentally swallows the eggs, large cysts may form in the body. E. vogeli is similar to the above but is more prevalent in Central and South America.

Important Points in Treatment

1. Echinococcosis can be prevented.  Periodic deworming of pets that are allowed to roam is recommended because the tapeworm is difficult to see in the stool due to its small size.

2. Echinococcosis should be suspected if a pet passes any type of tapeworm.

3. Children's sandboxes should be covered to prevent stray animals from defecating in them.  Good hygiene should be practiced (wash hands) after working in the garden or playing in the sand.

4. Hunters and others who work with wildlife should wash their hands well before eating or putting objects in their mouth.

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