Loiasis is a form of filariasis (see this term), caused by the parasitic worm Loa loa, endemic to the forest and savannah regions of Central and Western Africa. Loiasis may either be asymptomatic or manifest as a large, transient area of localized, non-erythematous subcutaneous edema (Calabar swellings), adult worm migration through the sub-conjunctiva (''African eye worm'') and pruritus. Generalized itching, hives, muscle pains, arthralgias, fatigue, and adult worms visibly migrating under the surface of the skin may be observed. Severe complications such as encephalopathy have been reported in highly infected individuals receiving ivermectin during mass drug administration programs for the control of onchocerciasis and lymphatic filariasis (see these terms).