Answer: This is a classic example of a Dipylidium caninum proglottid. Note the pores on either side of the proglottid (hence the name "double-pored dog tapeworm). Within the proglottid, you can observe numerous immature egg packets. These are highlighted below, with the inset showing the appearance of an immature egg packet that was expressed from a proglottid in a separate case. Note that the eggs contain refractile hooklets, like those seen in some other cestode eggs such as Taenia spp. and Hymenolepis spp. If you see hooklets in an egg, that's a sure sign that you are dealing with a cestode egg.
The history is also classic for infection with this cestode. Children and institutionalized adults are the most typically infected hosts, since infection is acquired through ingestion of an infected dog or cat flea.
Treatment with praziquantel is simple and effective in most cases. The Medical Letter provides an excellent discussion of treatment options.