Onchocerciasis :The world's second leading infectious cause of blindness'

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Onchocerciasis The world's second leading
infectious cause of blindness.
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Microfilaria is large and has no sheath
Onchocerca volvulus microfilariae from skin snips
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A long head space
Onchocerca volvulus microfilariae from skin snips
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A flexed tail
Onchocerca volvulus microfilariae from skin snips
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Onchocerciasis is present in 36 countries of
Africa, the Arabian peninsula and the Americans.
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As a public health problem the disease is most
closely associated with Africa, where it
constitutes a serious obstacle to socio-economic
development.
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Adult Onchocercus in section of tumour
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Onchocerciasis is often called "river blindness"
because of its most extreme manifestation and
because the blackfly vector-simulium- abounds in
fertile riverside areas, which frequently remain
uninhabited for fear of infection.
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Onchocerciasis. Microfilariae in the cornea.
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Onchocerciasis. Advanced cases, with corneal
scarring and pigment migration.
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Prevalence
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Out of some 120 million people world-wide who are
at risk of onchocerciasis, 96 are in Africa.
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Of the 36 countries where the disease is endemic,
30 are in sub-Sahara Africa (plus Yemen) and six
are in the Americas.
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A total of 18 million people are infected with
the disease and have dermal microfilariae, of
whom 99 are in Africa.
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Of those infected with the disease, over 6.5
million suffer from severe itching or dermatitis
and 270 000 are blind.
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Characteristics
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Onchocerciasis is caused by Onchocerca volvulus,
a parasitic worm that lives for up to 14 years in
the human body.
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Each adult female worm, thin but more than 1/2
metre in length, produces millions of
microfilariae (microscopic larvae) that migrate
throughout the body and give rise to a variety of
symptoms
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serious visual mpairment,including blindness
rashes, lesions, intense itching and
depigmentation of the skin lymphadenitis, which
results in hanging groins and elephantiasis of
the genitals and general debilitation.
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Onchocerciasis manifestations begin to occur in
persons one to three years after the injection of
infective larvae.
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Microfilariae produced in one person are carried
to another by the blackfly, which in West Africa
belongs to the Simulium damnosum species complex.
The blackfly lays its eggs in the water of
fast-flowing rivers.
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Adults emerge after 8-12 days and live for up to
four weeks, during which they can cover hundreds
of kilometres in flight.After mating, the female
blackfly seeks a bloodmeal and may ingest
microfilariae if the meal is taken from a person
infected with onchocerciasis.
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A few of these microfilariae may transform into
infective larvae within the blackfly, which are
then injected into the person from whom the next
meal is taken and subsequently develop into adult
parasites, thus completing the life cycle of the
parasite.
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The Onchocerciasis Control Programme (OCP)
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Onchocerciasis Elimination Program in the
Americas (OEPA) To coordinate onchocerciasis
control efforts in the 6 endemic countries of the
Americas and to reach the goal of eliminating
first the pathology and then the disease,
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the Onchocerciasis Elimination Programme for the
Americas (OEPA) was created in 1992 with the
support of PAHO, the Inter-American Development
Bank, a consortium of NGDOs, and all of the
affected countries.
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OCP was the first major programme developed to
control onchocerciasis. It was launched in 1974
in an area that originally encompassed seven
countries in West Africa.
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Onchocerciasis. Microfilaria in cutaneous tissues.
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Onchocerciasis. Nodule containing adult worm over
abdominal wall.
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Onchocerciasis. Thickened leathery skin over
lower back and buttocks of 50-year-old man.
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Onchocerciasis. Thickened leathery skin with
patchy depigmentation on the thighs of an African
man.
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Onchocerciasis. Section through a subcutanous
nodule showing a granulomatous lesion containing
numerous adult forms of Onchocerca volvulus.
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Onchocerciasis. Higher power of section through
female O. volvulus showing numerous immature
microfilariae within the uterus.
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Onchocerciasis. Microfilaria obtained after
immersing skin snip from infected individual in
saline solution.
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Onchocerciasis. Nodule containing adult worm
being surgically removed.
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Thank You