Which of these parasites is a tapeworm?

• A. Paranoplocephala mamillana
• B. Strongyloides westeri
• C. Parascaris equorum
• D. Oxyuris equi

Answer: (A)

Tapeworms (cestodes) are flat, ribbon-like parasites composed of a scolex for attachment and a chain of segmented proglottids; they lack a true digestive tract and absorb nutrients directly through their surface. Paranoplocephala mamillana fits this description as a cestode that infects the intestines of horses. Its life cycle involves an intermediate host (typically a mite), and the adult tapeworms reside in the equine gut, presenting as segmented bodies in feces or during examination. The other options are nematodes—roundworms with a tubular body and a complete digestive tract—so they do not have the same flat, segmental body plan. Strongyloides westeri, Parascaris equorum, and Oxyuris equi cause different diseases in horses and lack the characteristic tapeworm anatomy. Therefore, Paranoplocephala mamillana is the tapeworm.