Transcript Onchocerca volvulus

By Patrick Foote
 Is a nematode.
 Causes Ochocerciasis or “river blindness”
 Nematode does not cause blindness, but its
endosymbiont Wolbacia pipientis (bacteria)
 Second leading cause of blindness.
 Estimated 18 million suffer from Ochocerciasis, and
270,000 cases of blindness.
Taxonomy
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Kingdom
Phylum
Class
Order
Superfamily
Family
Genus
Species
Animalia
Nematode
Rhabditea
Spiruida
Filaroidea
Onchocercidae
Onchocerca
Volvulus
Hosts
 Definitive: Humans (only ones)
 Intermediate: Black fly (Simulium yahense)
Geographic
 Central and South America.
 Mainly Africa
Morphology
 Males are 19 to 42 cm long and 130 to 210 um wide.
 Females are 33.5 to 50 cm long and 270 to 400 um
wide.
 Infective larvae of O. volvulus are 500 micrometers by
25 micrometers
Life Cycle
Monsters Inside Me
 http://animal.discovery.com/videos/monsters-inside-
me-worms-in-my-eye.html
Pathogenesis
 Adult worm is least pathogenic.
 In Africa, found in pelvis region.
 In Americas, it is found above the waist.
 Sometimes causes enlargement of body parts and “
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hanging groin” which loses elasticity in skin.
Inflammation, can spread to nearby tissues (eye)
Itchy skin
Abnormal pigmentation.
Bacterial infection
Diagnosis
 Blood free skin snip (biopsy)
 Diagnosis is based on symptoms.
 History of exposure to black flies.
Treatment
 Treatment and control is done by Ivermectin.
 Ivermectin is effective in killing larvae, but does not
affect adult worm.
Control
 Vector control (black fly)
 Treatment of infected patients
 Avoidance of black fly.
 OCP “Ochocerciasis Control Program” launched in
1974. First tried larvacide on fast flowing rivers to
control them. No real effect.
 1988 treatment with Ivermectin for infected people,
eliminating it as public concern.
Questions:
 What is the definitive host of O. volvulus?
 How do you diagnose O. volvulus?
 What can this parasite cause?
 Where is the parasite found?
References:
 http://www.cdfound.to.it/html/onco2.htm
 http://www.brighthub.com/health/conditions-
treatments/articles/20195.aspx
 http://pathmicro.med.sc.edu/parasitology/nematodes
.htm
 http://animal.discovery.com/videos/monsters-insideme-worms-in-my-eye.html