Dipylidium caninum in a 4-month old male.

Dipylidium caninum, known as the double-pored dog tapeworm, is a parasite that commonly infects dogs and cats worldwide. Humans may be an accidental host if the infective stage, the cysticercoid larva, is ingested. Although rare, it is more commonly seen in infants and children. This case study involves an infant misdiagnosed with pinworm infection twice before a laboratory evaluation was able to confirm Dipylidium caninum. Accurate diagnosis is important, as treatment for pinworm infection will not eliminate Dipylidium caninum.