Parasitology - Onchocerca volvulus

2. Adults
Live in the nodules for approximately 15 years
Female is larger than male
Female worms are capable of producing
microfilariae in the subcutaneous nodules for
approximately 9 years

3. Microfilariae
Unsheathed
Life span: may reach 2 years
Ingested by a blackfly
Occasionally found in peripheral blood, urine,
and sputum
Typically found in skin and lymphatics of
connect tissues

4. Onchocerca volvolus

5. Onchocerca volvolus

6. Causes Onchocerciasis
“River Blindness” – fertile riverside areas
Blindness in many African Countries
West and Central Africa
Onchocerca volvolus
Yemen and six countries in Latin America
Blindness in many African Countries
Half a million blind people

7. Manifestation
Pruritus – severe itching pf the skin
Dermatitis – inflammation of the skin
Onchocercomata – adult form fibrous capsules
in the subcutaneous nodules
Onchocerca volvolus
Lymphadenopathies – disease in the lymph
nodes
Ocular Lesions – could cause blindness

8. Diagnosis
Skin snips - microfilariae
Corneal-scleral punch (Scalpel and needle)
Sample
Onchocerca volvolus
Incubate for 30mins-2hours in saline or
culture medium
Examined for microfilariae that would
have migrated from the tissue to the
liquid phase of the specimen

9. Other methods
Those with Ocular Lesions
Slit Lamp Examination (Microfilaria)
Substanciapropria of the cornea
Anterior chamber
Onchocerca volvolus
Tissue Samples in Nodulectomies (Adult Worms)
Africa : Trunk and Limbs (Simulium Bite Limbs)
America : Head particulary over the scalp (Bite
Head Region and Neck)