**Core Concept**
Calabar swellings are a type of skin manifestation characterized by localized, episodic edema and are associated with a specific filarial infection. This phenomenon is a result of the immune response to the migrating adult worm.

**Why the Correct Answer is Right**
Loa loa, also known as the African eye worm, is a species of filarial parasite that causes loiasis. The adult worm migrates through the subcutaneous tissues, leading to the development of Calabar swellings. These swellings are caused by the immune response to the worm, which results in the activation of eosinophils and the release of histamine, leading to increased vascular permeability and edema.

The adult Loa loa worm is known to migrate through the body, often causing these characteristic Calabar swellings, which are typically seen in the limbs or face. The worm's migration is thought to be triggered by changes in temperature and humidity.

**Why Each Wrong Option is Incorrect**
**Option A:** Onchocerca volvulus is responsible for causing onchocerciasis, also known as river blindness, which primarily affects the eyes and skin, but does not cause Calabar swellings.

**Option C:** Brugia malayi is a causative agent of lymphatic filariasis, which affects the lymphatic system and causes elephantiasis, but is not associated with Calabar swellings.

**Option D:** Wuchereria bancrofti is also a causative agent of lymphatic filariasis, similar to Brugia malayi, and is not associated with Calabar swellings.

**Clinical Pearl / High-Yield Fact**
It's worth noting that Calabar swellings are typically seen in individuals infected with Loa loa and are often accompanied by other symptoms such as itching, rash, and eye lesions. This unique presentation can help clinicians diagnose loiasis.

**✓ Correct Answer: B. Loa loa**