Which parasite is known as the large American liver fluke?

• A. Stephanurus
• B. Fascioloides
• C. Alaria
• D. Metastrongylus

Answer: (B)

Fascioloides magna is the large American liver fluke. It’s a trematode that resides in the bile ducts of deer and other ruminants in North America, and it earns the descriptor “large” to distinguish it from other liver flukes like Fasciola hepatica. Its life cycle involves a snail as the intermediate host, with eggs shed in bile and feces to continue the cycle. This makes it a true liver fluke, unlike the other options listed: Stephanurus dentatus is a kidney worm (a nematode) of pigs; Alaria spp. are intestinal trematodes with a different host range and life cycle; Metastrongylus is a lungworm of pigs. Therefore, the parasite known as the large American liver fluke is Fascioloides magna.