Clinical Presentation in Humans

Initial Presentation
Symptoms occur between one to three years after initial infection. Early indications of onchocerciasis include fever, joint pain and skin welts (hives). Nearly 10% of infected individuals are asymptomatic.

Cutaneous Presentation
The skin is the principal site of infection.  Intense irritation and itching of skin occurs as the body responds to O. volvulus antigens.  This inflammation eventually leads to the thickening and cracking of skin. Loss of elasticity occurs due to the thickening of skinand eventually atrophy of skin and wrinkling occurs.  More severe reactions occur as infections persist.

Subcutaneous nodules (onchocercomas) are a significant indicator of infection and appear in 30% of all cases. Nodules develop over a 18-month span and vary in size and number. Nodule location depends on the location of the black fly bite. In Africa the nodules are mainly found on the lower trunk and pelvic region while in the Americas the head and neck are the most affected regions.

Many more types of cutaneous lesions occur regionally. Some examples of these are:

    Sowda is a severe cutaneous reaction in which skin gets dark, thick, itchy and covered with scaly papules. It was originally seen in Yemen but can now be found in Central America, West Africa, and the Sudan.

Man demonstrating the difference in color and appearance of his hands due to sowda. One hand is significantly darker and thicker.

Photo courtesty of WHO/TDR/Crump

Erisípela de la costa
Macular rash with edema of the face, typically on one side of the face. Acute lesion that is found in Latin America


Mal morado
Reddish-blue discoloration on trunk and arms. Another acute cutaneous lesion found in Latin America. [I]

Women with erisipela-swollen cheek and rash .
Photo courtesy of MediUAQ.


Standardized system of symptom classification
The following classifications of onchocerciasis symptoms were created to ensure uniformity for data collection and studies.


Acute Papular onchodermatitis (APOD)
    Solid or speckled papular rash with the possibility of vesicles.

Child who has the early stage skin infection.
Photo courtesy of WHO/TDR/Crump

Chronic papular onchodermatitis (CPOD)
    Scattered, hyperpigmented, flat-topped papular rash with larger diameter papules than APOD.

Women with advanced dermatitis.

Photo courtesy of WHO/APOD/TDR/Crump

Lichenified Onchodermatitis (LOD)
     Raised, hyperpigmented plaques that appear with lymphadenopathy.

Legs with rash and spots of depigmentation.
Photo courtesy of WHO/TDR/Smyth

    Wrinkling and dryness of skin. particularly noticeable in younger individuals.

Wrinkled and dry skin.
Photo courtesy of WHO/TDR/Baldry

     Partial loss of pigment around hair follicles.  Leopard skin is the complete loss of pigment around the hair follicle and is usually found on the shins.  Elderly individuals are especially susceptible to leopard skin.     

Severe depigmentation of shins characteristic of leopard skin.

Photo courtesy of WHO/TDR/Ngoumou

    Inflammation of the lymph nodes that results in swelling.  In African cases of onchocerciasis the affected sites are the femoral and inguinal nodes (groin area) while in the Americas the lymph nodes of the head and neck are affected.

Female with lymphadenitis and the beginnings of hangin groin.

Photo Courtesy of WHO/TDR/Murdoch

  Hanging groin
Skin in groin area is atrophied and inelastic, resulting in sagginess.  Possible enlarged lymph nodes. [II]

Male with hanging groin and some dermatitis.

Photo courtesy of WHO/TDR



  Ocular Presentation

 Ocular lesions
Eye involvement occurs during chronic onchocerciasis because of the migration and death of microfilariae in the eye tissues.  5% of all onchocerciasis cases result in ocular lesions. Conjuctivitis often is the first reaction to the microfilariae. Dead microfilariae also cause corneal infections that can result in scelerosing keratitis and vascularization. Sclerosing keratitis is the main cause of blindness in onchocerciasis cases.  Other effects of microfilariae migration include glaucoma, iritis, iridocyclitis, optic neuritis, and papillitis. 500,000 people are blind or have impaired vision and 270,000 have irreversible blindness because of onchocerciasis. [I,v]

An eye blinded by microfilariae.

Photo courtesy of WHO/TDR