## **Core Concept**
Eosinophilic meningoencephalitis is a condition characterized by the presence of eosinophils in the cerebrospinal fluid (CSF) and inflammation of the brain and meninges. This condition is often associated with parasitic infections, among other causes. The presence of eosinophils in the CSF is a key diagnostic feature.

## **Why the Correct Answer is Right**
The correct answer, **Angiostrongylus cantonensis**, is a parasitic nematode that causes eosinophilic meningoencephalitis. This parasite is commonly found in rats and can be transmitted to humans through the consumption of contaminated food or water. Once in the human host, the larvae migrate to the central nervous system (CNS), leading to an inflammatory response that includes the recruitment of eosinophils. The presence of eosinophils in the CSF is a hallmark of this condition.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although certain protozoa and fungi can cause meningoencephalitis, they are not typically associated with eosinophilic meningoencephalitis.
- **Option B:** This option is incorrect as it does not specify a known cause of eosinophilic meningoencephalitis.
- **Option D:** This option is incorrect because, while other parasites can cause CNS infections, they are not specifically known for causing eosinophilic meningoencephalitis.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that eosinophilic meningoencephalitis should be suspected in patients with a history of travel, consumption of raw or undercooked seafood or meat, and presentation with symptoms of meningoencephalitis along with eosinophilia in the CSF. Early diagnosis and treatment are crucial to prevent long-term neurological damage.

## **Correct Answer:** . **Angiostrongylus cantonensis**