This article describes a case of enteritis in a 3.5-yr-old child with persistent diarrhea and the isolation of three gastrointestinal pathogens, including a rare human pathogen Hymenolepis diminuta (rat tapeworm). This is the first reported case in the northeastern United States in 20 yr and demonstrates that persons living in homes infested with rodents and arthropods are at risk of acquiring this infection.