Loa loa is a parasitic worm that causes the disease known as loiasis, primarily found in parts of West and Central Africa. It is transmitted to humans through the bite of infected mango flies, which are also known as Chrysops flies. The adult worms can live in the human body for several years, often migrating through the subcutaneous tissues and occasionally entering the eye. Symptoms of loiasis can include swelling, pain, and itching at the site of the worm's migration. In some cases, the worm may be visible in the eye, leading to potential vision problems. Treatment typically involves medication to kill the adult worms and alleviate symptoms.