If we look at the life cycle, the adult tapeworm (only about two inches long) passes eggs onto the ground within feces. One of many rodents consumes the egg(s). The egg hatches in the intestine and migrates to an organ (most commonly the liver or lung) and a hydatid cyst is formed. As a second stage larva, it can asexually reproduce to become as many as 400 second stage larva in the cyst. If this rodent is then consumed by a coyote, fox, dog or cat, the larva will hatch and attach to the intestinal wall. An adult tapeworm will then produce eggs and the cycle continues.

If a human accidentally consumes the egg, it also migrates and forms a cyst in an organ (again, usually the lung or liver). The cysts can grow to be the size of a baseball or softball. This cyst can go unnoticed in the body for years. Bayer Animal Health detail document #D05063 states that mortality in humans is high and that 93% of patients are dead in 10 years,

Usually when a dog or cat has tapeworms, the clients tell the veterinarian about it because they see the "white rice" like parasites in the feces or hanging from the animal’s back end. What is being seen is the proglotid segments that contain the eggs of the tapeworm, however, with Echinococcus the proglotids are microscopic and can not be seen with the naked eye. The parasite is therefore much more dangerous because the owner will not know the pet is infected.

Attention has also been called to a round worm called Baylisascaris procyonis. Human cases have been on the rise in our country and it can be fatal to children, especially those under two years of age.