Loiasis

 Migration of adult worm

Migration of adult worm

Loiasis, also known as African eye worm, is caused by the parasitic worm Loa loa and affects over 10 million people, mostly in West and Central Africa. Loiasis 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 the appearance of the adult worm in the eye, the infection is most commonly associated with recurrent episodes of itchy swellings (local angioedema) known as Calabar swellings.

Loa loa is not being addressed by any elimination programs and represents a major public health issue. Its story is closely intertwined with that of another disease: river blindness.  The fight against river blindness relies on mass administration of over 100 million annual doses of ivermectin, a de-worming drug with an exceptional safety record, except in people suffering from loiasis.  The worm Loa loa produces an incredible progeny and in extreme cases over 500 million embryos can circulate in the bloodstream of an infected patient. Ivermectin rapidly kills all the embryos and the necrotic embryos can lead to a life-threatening inflammatory response.  The presence of Loa loa infection has limited programs to control or eliminate river blindness (a.k.a. onchocerciasis) and lymphatic filariasis (learn more on Wikipedia, on the CDC website, or in this 2013 Lancet article).

DDTD has developed a rapid diagnostic test designed for the high resolution mapping of L. loa. We hope that the maps will help accelerate the elimination of river blindness and lymphatic filariasis, and eventually form the basis of elimination programs direct against loiasis itself.  It is our belief that in the 21st century, no one should live with worms and millions of embryos in their body. 

  Overlap of loiasis (black-and-white pie charts) and onchocerciasis (color map). Loiasis was mapped with the Rapid Assessment Procedure for Loa (RAPLOA) where villagers are asked for a history of worms in the eyes in their village. The Rapid Epidemiological Mapping of Onchocerciasis (REMO) is done by monitoring the prevalence of nodules caused by subcutaneous “nests” of adult  O. volvulus  worms. Credit: We thank Dr. Zouré of the WHO for generating this map upon our request (November 2014).

Overlap of loiasis (black-and-white pie charts) and onchocerciasis (color map). Loiasis was mapped with the Rapid Assessment Procedure for Loa (RAPLOA) where villagers are asked for a history of worms in the eyes in their village. The Rapid Epidemiological Mapping of Onchocerciasis (REMO) is done by monitoring the prevalence of nodules caused by subcutaneous “nests” of adult O. volvulus worms. Credit: We thank Dr. Zouré of the WHO for generating this map upon our request (November 2014).