Microfilaria: Onchocerca volvulus
Vector: Simulium (blackflies)
Clinical findings:
(1) skin changes (see below)
(2) lymphadenitis: "hanging groin" from inguinal and femoral lymphadenopathy
(3) ocular findings: keratitis, chorioretinitis, anterior uveitis, visual impairment, bilateral blindness
(4) eosinophilia
(5) disability from visual impairment or dermatitis
Skin changes:
(1) subcutaneous nodules (onchocercomas) on head, chest, back, hips and/or limbs
(2) chronic dermatitis with lichenification and papules, including sowda (chronic hyperreactive papular dermatitis)
(3) chronic pruritis
(4) skin atrophy and loss of skin elasticity, with wrinkling
(5) hyper and/or hypopigmentation (mal morado, leopard skin)
Diagnostic tests:
(1) multiple (up to 6 or 7) skin snips to demonstrate microfilaria in dermis and subcutaneous tissue, with PCR the most sensitive method
(2) slit lamp examination in cornea or anterior chamber of the eye (best done after the patient places his or her head between the knees for 10-15 minutes before the examination)
(3) biopsy of subcutaneous nodules to demonstrate adult worms, or ultrasound (central homogeneous area with dense particles and a lateral acoustic shadow)
(4) patch test with diethylcarbamazine (DEC)
