This study will evaluate and treat patients with filarial infections to explore in depth the immunology of the disease, including susceptibility to infection, disease development, and response to treatment. Filarial infections are caused by parasitic worms. The immature worm (larva) is transmitted to a person through a mosquito bite and grows in the human body to 2 to 4 inches in length. Although many of these infections do not produce symptoms, especially in the early stages of infection, others can have serious consequences, including swelling of the limbs or genitalia, allergic-lung problems, skin rash, eye inflammation that can lead to blindness, and heart disease. This protocol does not involve any experimental diagnostic procedures or treatments, and will use only procedures employed in the standard practice of medicine.