Answer to Case 521

Answer:Dicrocoelium dendricitumeggsThis is relatively rare find in human stool specimens. The eggs are small (35-45 µm long by 20-30 µm wide), thick-walled, and often brown due to bile staining. They are shed in a fully embryonated state, with the embryo often easily seen within the egg (these look like a skull to me!)D. dendricitumis such a fascinating parasite. Its life cycle typically involves as ruminant, a snail and an ant. The whole life cycle is nicely illustrated by the CDC DPDx groupHERE. Here is the accompanying text: Ruminants are the usual definitive hosts forDicrocoelium dendricitum, although other herbivorous animals, carnivores, and humans can serve as definitive hosts. Embryonated eggs are shed in feces. The eggs are ingested by a snail. Many species of snail may serve as the first intermediate host, includingZebrinaspp. andCionellaspp. When the miracidia hatch, they migrate through the gut wall and settle into the adjacent vascular connective tissue, where they become mother sporocysts. The sporocysts migrate to the digestive gland where they give rise to several daughter sporocysts. Inside each daughter sporocyst, cercariae are produced. The cercariae migrate to the respiration chamber where they are shed in slime ball from the snail. After a slime ball is ingested by an ant, the cercariae become free in the intestine and migrate to the hemocoel where they become metacercariae. Many ants may serve as the second intermediate host, especially members of...
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs