Loiasis, also known as African eye worm, is caused by the parasitic worm Loa loa. It is transmitted through the repeated bites of deerflies (also known as mango flies or mangrove flies) of the genus Chrysops. The flies that transmit the parasite breed in the high-canopied rain forest of West and Central Africa. In addition to eye worm, the infection is most commonly associated with recurrent episodes of itchy swellings (local angioedema) known as Calabar swellings. Recognition of Loa loa infections has become more important in Africa because the presence of Loa loa infection has limited programs to control or eliminate onchocerciasis and lymphatic filariasis.

Image: L: Microfilaria of L. loa in a thin blood smear, stained with Giemsa. R: Picture of Chrysops silacea feeding on a volunteer. Credit: DPDx