Onchocerciasis

Introduction

Onchocerciasis is a chronic parasitic disease caused by filarial nematode Onchocerca volvulus 

-it is transmitted by female blackflies near free-flowing rivers and streams 

-Most cases are in tropical Africa and Central America 

-Larvae deposited by the blackfly mature into adult worms in subcutaneous tissue and form skin nodules. Females produce microfilariae which migrate to the eyes and cause serious eye disorders. 

Symptoms & Signs 

Onchocerciasis is characterized by dermal, ocular and lymphatic manifestations

Dermal: Subcutaneous nodules over bony prominences (onchocercomata), intensely pruritic papular rash, skin atrophy, scaly dermatitis feeling like ‘lizard skin’ or ‘leopard skin’, loose pelvic skin described as ‘hanging groin’ 

Ocular: most serious manifestations of onchocerciasis; photophobia,   conjunctivitis, keratitis, uveitis, retinochoroiditis, iridocyclitis, optic atrophy, glaucoma, and blindness (river blindness) 

Lymphatic: Inguinal and femoral lymphadenopathy

Diagnosis 

Identification of microfilariae: in skin snips, in nodule biopsy or in the urine, but not in blood 

Eye: Slit-lamp examination revealing microfilariae in the eye 

Mazzotti test: Exacerbation of skin rash and pruritus after administration of diethylcarbamazine 

Other tests: PCR

Treatment 

-Ivermectin (drug of choice) kills microfilariae, not adult worms 

-Suramin kills adult worms 

Other agents: Moxidectin, doxycycline 

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