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| Keywords: Echinococcus Life Cycle.png The adult Echinococcus granulosus 3 to 6 mm long 1 resides in the small bowel of the definitive hosts dogs or other carnivores Gravid proglottids release eggs 2 that are passed in the feces After ingestion by a suitable intermediate host under natural conditions sheep goat swine cattle horses camel the egg hatches in the small bowel and releases an oncosphere 3 that penetrates the intestinal wall and migrates through the circulatory system into various organs especially the liver and lungs In these organs the oncosphere develops into a cyst 4 that enlarges gradually producing protoscolices and daughter cysts that fill the cyst interior The definitive host becomes infected by ingesting the cyst-containing organs of the infected intermediate host After ingestion the protoscolices 5 evaginate attach to the intestinal mucosa 6 and develop into adult stages 1 in 32 to 80 days The same life cycle occurs with E multilocularis 1 2 to 3 7 mm with the following differences the definitive hosts are foxes and to a lesser extent dogs cats coyotes and wolves; the intermediate host are small rodents; and larval growth in the liver remains indefinitely in the proliferative stage resulting in invasion of the surrounding tissues With E vogeli up to 5 6 mm long the definitive hosts are bush dogs and dogs; the intermediate hosts are rodents; and the larval stage in the liver lungs and other organs develops both externally and internally resulting in multiple vesicles E oligarthrus up to 2 9 mm long has a life cycle that involves wild felids as definitive hosts and rodents as intermediate hosts Humans become infected by ingesting eggs with resulting release of oncospheres in the intestine and the development of cysts in various organs Image adapted from original available at the United States Centres for Disease Control Parasitology Identification Laboratory http //www dpd cdc gov/dpdx/HTML/ImageLibrary/Echinococcosis_il htm PD-USGov Echinococcus life cycle biology | ||||
