|Description:||This photomicrograph revealed some of the ultrastructural morphology exhibited by an adult cestode, Echinococcus granulosus, which had been found in a dog. E. granulosus causes what is known as “cystic echinococcosis”. As dogs and other canids are the only definitive hosts for Echinococcus, adults are not expected to be found in the human host. Adults range from 3mm - 6mm in length and usually consist of a scolex, and three proglottids. The third (terminal) proglottid is gravid, and is longer than wide, as can be seen in this instance. The scolex contains four suckers and a rostellum with 25 - 50 hooks.|
Being that dogs and other canids are the definitive hosts for Echinococcus spp., humans are only infected by the larvae after ingestion of eggs from food, water or fomites contaminated with dog feces. Upon ingestion of the eggs by the human host, the oncospheres migrate from the intestinal lumen to other body sites where they develop into hydatid cysts. These cysts can be found in any part of the body, but are most common in the liver, lung and central nervous system.