Alveolar Hydatid Disease

(al-VEE-oh-ler HIGH-dad-id)

What is Alveolar Hydatid disease (AHD)?

AHD (al-VEE-oh-ler HIGH-dad-id) disease results from being infected with the larval stage of Echinococcus multilocularis, a microscopic tapeworm (1-4 millimeters) found in foxes, coyotes, dogs, and cats. Although human cases are rare, infection in humans causes parasitic tumors to form in the liver, and, less commonly, the lungs, brain, and other organs. If left untreated, infection with AHD can be fatal.

Where has AHD been found?

AHD is found worldwide, mostly in northern latitudes. Cases have been reported in central Europe, Russia, China, Central Asia, Japan, and North America. In North America E. multilocularis is found primarily in the north central region from eastern Montana to central Ohio, as well as Alaska and Canada. Human cases have been reported in Alaska, the province of Manitoba, and Minnesota. Prevalence among wild foxes and coyotes is high, and may reach over 50% in some areas; however, even in these areas, transmission to humans has been low.
How does infection occur in foxes, coyotes, dogs, and other cats?

Wild foxes, coyotes, and cats get infected when they eat Echinococcus multilocularis larvae in infected rodents, field mice, or voles. Cats are less susceptible than dogs, but because they probably catch and eat rodents more often, may also become infected. Once the animal becomes infected, the tapeworm matures in its intestine, lays eggs, and the infected animal passes eggs in the stool. These tapeworm eggs, which are directly infectious to other animals, are too tiny to see, and will stick to anything with which they come in contact. Coyotes, foxes, dogs, and cats are not harmed by the tapeworm and do not have symptoms of AHD.
Can animals be tested for E. multilocularis tapeworms?

Routine fecal examinations are not sufficient to diagnose E. multilocularis infection. Infection with the E. multilocularis tapeworm and other tapeworms may occur at the same time. Eggs of Taenia species tapeworms and Echinococcus tapeworms are similar in shape and size and are very difficult to tell apart. If you live in an area where this parasite occurs or you are concerned about your dog or cat being infected with E. multilocularis or other tapeworms, see your veterinarian who can answer your questions and assess the risk of possible infection.
How can I be infected with AHD?

By accidentally swallowing the eggs of the E. multilocularis tapeworm. Humans can be exposed to these eggs in two main ways, both of which involve "hand-to-mouth" transfer or contamination:

* By directly ingesting food items contaminated with stool from foxes or coyotes. This might include grass, herbs, greens, or berries gathered from fields.* By petting or handling household cats and dogs infected with the E. multilocularis tapeworm. These pets may shed the tapeworm eggs in their stool, and their fur may be contaminated. Some dogs "scent roll" in foreign material (such as wild animal feces) and may become contaminated this way.