Neglected Tropical Diseases

The NTD Initiative

Onchocerciasis

Symptoms

• Adult worms contained in subcutaneous nodules initially evoke a non-inflammatory response with few clinical symptoms.³
  
  
• Actual symptoms are mainly caused by the inflammatory response of infected persons to the microfilarial stage of the onchocerciasis parasite. Severely infected individuals usually have one or both of the following conditions: dermatitis and eye lesions (keratitis and chorioretinitis).³
  
• Skin involvement (See photo above) typically ranges from intense itching, swelling, and inflammation to skin atrophy and depigmentation. The pruritus (itching) from onchocerciasis is very severe, intractable, and non-responsive to antipruritus medication. Scratching, excoriation to the point of bleeding, and even suicide can occur in heavily infected persons.
  
• Ocular involvement in its most severe form leads to blindness. The microfilariae migrate to the surface of the cornea.^1;2 Participation of all tissues of the eye has been described.
  
• Punctate keratitis (condition in which the eye's cornea, the front part of the eye, becomes inflamed) occurs in the infected area but clears up as the inflammation subsides.
  
• However, if the infection is chronic, sclerosing keratitis can occur, making the affected area opaque. Over time the entire cornea may become opaque, thus leading to blindness. There is some evidence to suggest that the effect on the cornea is caused by an immune response to the bacteria (endosymbiont Wolbachia) present in the worms.
  
• Additionally, inflammation of the retinal pigment can also lead to chorioretinitis, chorioretinal atrophy, and posterior ocular diseas

Learn more about onchocerciasis:

• Epidemiology
• Life Cycle
• Diagnosis
• Treatment and Control
• Back to Onchocerciasis Overview

References

1. Hoerauf A., Buttner DW, Adjei O, et al: Onchocerciasis. BMJ 326:207, 2003.
2. Dadzie KY, Remme J, Rolland A, et al: Ocular Onchocerciasis and intensity of the infection in the community. II. West African rainforest foci of the vector Simulium yahense. Trop Med Parasitol 40:348, 1989.
3. Dadzie KY, Remme J, Backer RH, et al: Ocular Onchocerciasis and intensity of the infection in the community. III. West African rainforest foci of the vector Simulium sanctipauli. Trop Med Parasitol 41:376, 1990.