A patient with fatigue, eosinophilia, and periorbital edema has symptoms that mimic infectious mononucleosis. Which parasite should be considered in the differential?

• A. Ascaris lumbricoides
• B. Taenia solium
• C. Trichinella spiralis
• D. Trypanosoma cruzi

Answer: (C)

The main idea here is that eosinophilia together with periorbital edema points to a tissue-dwelling helminth infection, not a viral illness. Trichinella spiralis classically causes periorbital edema, fatigue, fever, and muscle pains after eating undercooked pork or game meat. As larvae migrate and encyst in skeletal muscle, they trigger an inflammatory response that leads to muscle swelling and eosinophilia. This combination—eye-area edema plus eosinophils—is a classic clue for trichinellosis, making Trichinella spiralis the best fit for the differential.

Other parasites listed don’t align as well with this specific pattern. Taenia solium is a tapeworm with different presentations, often involving intestinal symptoms or cysticercosis. Ascaris lumbricoides can cause eosinophilia but typically presents with gastrointestinal or pulmonary symptoms rather than periorbital edema. Trypanosoma cruzi can cause acute signs like eyelid edema in Romana’s sign, but the overall picture and the strong association of periorbital edema with trichinellosis make Trichinella spiralis the most likely match.