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A chronic disease caused by the filarial nematode Loa loa, with symptoms and signs first occurring approximately 3-4 years after a bite by an infected tabanid fly. When the infective larvae mature, the adult worms move about in an irregular course through the connective tissue of the body (as rapidly as 1 cm/minute), frequently becoming visible beneath the skin and mucous membranes; for example, in the back, scalp, chest, inner surface of the lip, and especially on the conjunctiva. The worms provoke hyperemia and exudation of fluid, often a host response to the worm products, a Calabar or fugitive swelling that causes no serious damage and subsides as the parasites move on; the patient is annoyed by the "creeping" in the tissues and intense itching, as well as occasional pain, especially when the swelling is in the region of tendons and joints. Many patients have marked eosinophilia (10-40%).
Calabar swellingA transient allergic response to microfilariasis by Loa loa, as well as Dipetalonema perstans, which was first described in Africa.
Cryosops silacea and C dimidiata, haematophagous flies of the rain forest.