February 1 - Echinococcus granulosis

When people think of tapeworms, they often think of very long ones, like Taenia saginata. Echinococcus granulosis is a tiny tapeworm – tiny, but nasty. The main vertebrate hosts of E. granulosis are canids, where the 5 millimeter-long adult tapeworms live in the small intestine. Eggs are expelled in the dog’s feces, where they are eaten by herbivores such as sheep or deer or rodents. Inside the herbivore, the larvae travel through the intermediate host’s blood and take residence in various organs where they form hydatid cysts, which can grow very large in some cases – as big as a grapefruit or even larger. It is thought that these cysts make the herbivore more vulnerable to predation by – canids, of course. Humans can serve as intermediate hosts if they are exposed to contaminated dog (or coyote or wolf or other canid) feces and will suffer from hydatid disease when the larval tapeforms form cysts in our organs. This can be a serious condition, not only because the large cysts can put pressure on organs, but also because should the cysts rupture within the body, a person can suffer from severe shock. The disease can be common in areas with many sheep.