**Core Concept**
Eosinophilic meningoencephalitis is a rare inflammatory condition affecting the brain and meninges, characterized by an excessive eosinophilic response, often associated with parasitic infections.

**Why the Correct Answer is Right**
The correct answer is D. Angiostrongylus cantonensis, also known as the rat lungworm, is a parasitic nematode that causes eosinophilic meningoencephalitis upon ingestion of contaminated food or water. The parasite migrates through the central nervous system, triggering a severe eosinophilic reaction, leading to inflammation and damage to the brain and meninges.

**Why Each Wrong Option is Incorrect**
* **Option A:** Gnathostoma spinigerum is a parasitic nematode that causes gnathostomiasis, primarily manifesting as skin and soft tissue infections, rather than eosinophilic meningoencephalitis.
* **Option B:** Naegleria fowleri is an amoeba that causes primary amebic meningoencephalitis, a different and more acute form of meningoencephalitis.
* **Option C:** Toxocara canis is a parasitic nematode that causes toxocariasis, primarily affecting the eyes, lungs, and liver, rather than the central nervous system.

**Clinical Pearl / High-Yield Fact**
Eosinophilic meningoencephalitis caused by Angiostrongylus cantonensis can be difficult to diagnose, and treatment is often challenging, requiring antiparasitic medication and supportive care.

**Correct Answer:** D. Angiostrongylus cantonensis