Onchocerciasis (river blindness)

Eyes | Ophthalmology | Onchocerciasis (river blindness) (Disease)


Onchocerciasis is an eye and skin disease caused by the filarial parasitic worm Onchocerca volvulus. Adult worms remain in subcutaneous nodules, limiting access to the hosts immune system. Microfilariae, in contrast, are able to induce intense inflammatory responses, especially upon their death. Dying microfilariae have been recently discovered to release Wolbachia surface protein that activates TLR2 and TLR4, triggering innate immune responses and producing the inflammation and its associated morbidity.

Ocular involvement provides the common name associated with onchocerciasis, river blindness, and may involve any part of the eye from conjunctiva and cornea to uvea and posterior segment, including the retina and optic nerve. The microfilariae migrate to the surface of the cornea. Punctate keratitis occurs in the infected area. This clears up as the inflammation subsides.

Causes and Risk factors

Onchocerciasis is transmitted to humans through the bite of the blackfly. These flies breed in fast-flowing streams and rivers, increasing the risk of infection to individuals living nearby, hence the common name of river blindness. Within the human body, the adult female worm (macrofilaria) produces thousands of baby or larval worms (microfilariae), which migrate in the skin and the eye and are the cause of morbidity.

Diagnosis and Treatment

Ivermectin is the drug of choice in the treatment of onchocerciasis. Surgery to remove the infected skin nodules is also performed.