Image and content excerpted from the VisualDx clinical decision support system.
VisualDx images show variation in age, skin color, and disease stage. VisualDx has 11 images of Onchocerciasis.
Full text and additional images for Onchocerciasis are available in the following VisualDx packages:
125.3 – Onchocerciasis
B73.00 – Onchocerciasis with eye involvement, unspecified
SynopsisOnchocerciasis, a chronic parasitic disease, is also known as river blindness and sowda. It is caused by Onchocerca volvulus, a tissue nematode transmitted by the black fly (Simulium) in Africa, Latin America, and the Middle East.
Exposure occurs along riverbanks and streams where the black fly vector can be found. The time from infection to evolution of the first skin symptoms is anywhere from 8–20 months after the infective bite. The adult worms reside in subcutaneous nodules where they produce microfilariae for 10 years or more. However, patients can present with intermittent pruritus without apparent rash as their only dermatologic manifestation. The severity of skin manifestations may be related to parasite burden as well as host immunity.
Inflammation from the death of the microfilariae leads to intraocular scarring and blindness as well as skin atrophy, loss of elasticity, and hypopigmentation. Nodules located in the head/neck region are thought to be associated with an increased risk of blindness, presumably because of proximity to the eyes.
Travel-related infection is rare and is usually associated with long-term travel in rural areas (especially missionaries or researchers). Up to 50% of patients with onchocerciasis in endemic areas develop ophthalmic complications.
Many initial infections occur in childhood and remain silent for many years.