Which parasite is a protozoan parasite often implicated in intestinal infections in animals?

• A. Coccidia
• B. Heartworm
• C. Tapeworm
• D. Flea

Answer: (A)

Protozoan parasites that invade the intestinal lining are a common cause of intestinal infections in animals, and the classic example is coccidia. These single‑celled organisms, including genera such as Eimeria and Isospora, infect the intestinal epithelium and reproduce inside cells, leading to diarrhea, dehydration, and poor weight gain—especially in young animals. They are transmitted when animals ingest oocysts shed in feces, so controlling environmental contamination is key to prevention. In contrast, heartworm is a heart- and lung–affecting nematode, tapeworms are flatworms living in the gut but not protozoa, and fleas are external ectoparasites. Because the question specifies a protozoan parasite often implicated in intestinal infections, coccidia is the best fit.