FAQS
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Definition
of the disease
Onchocerciasis
-- the world's second leading infectious cause of blindness
-- is present in 36 countries of Africa, the Arabian
peninsula and the Americas. As a public health problem
the disease is most closely associated with Africa,
where it constitutes a serious obstacle to socio-economic
development. Onchocerciasis is often called "river
blindness" because of its most extreme manifestation
and because the blackfly vector abounds in fertile riverside
areas, which frequently remain uninhabited for fear
of infection.
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Transmission
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. 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. 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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Symptoms
Onchocerciasis
is caused by Onchocerca volvulus, a parasitic
worm that lives for up to 14 years in the human body.
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: serious visual impairment,
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. Onchocerciasis manifestations
begin to occur in persons one to three years after the
injection of infective larvae.
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Prevalence
Out
of some 120 million people world-wide who are at risk
of onchocerciasis, 96% are in Africa.
Of the 36 countries where the disease is endemic,
30 are in sub-Sahara Africa (plus Yemen) and six are
in the Americas.
A total of 18 million people are infected with the
disease and have dermal microfilariae, of whom 99% are
in Africa.
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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Treatment
The
development of ivermectin in the 1980's provided for
the first time a safe, effective drug capable of reducing
the numbers of skin microfilariae in infected people
and resulting in clinical improvement and decreased
transmission of infection by killing the larval worms
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The
Onchocerciasis Control Programme (OCP)
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. In 1986 the programme
was extended to include four additional countries, bringing
the current total of participating countries to 11.
The total operational area covers 1.23 million sq. km
and a combined population of about 30 million people.
The
programme has been jointly sponsored by WHO, the World
Bank, the United Nations Development Programme and the
Food and Agriculture Organization and is supported by
a coalition of more than 20 donor countries and agencies.
WHO acts as the Executive Agency for the programme,
while the World Bank is responsible for mobilizing resources
and administering the OCP Trust Fund. The Programme
is scheduled to come to an end by the year 2002. The
estimated total cost for the programme will be US$550
million, or less than US$1 per year for each protected
person.
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Global
control
OCP's
principal method for controlling onchocerciasis has
been to break the cycle of transmission by eliminating
the black fly. Simulium larvae are destroyed by application
of selected insecticides through aerial spraying of
breeding sites in fast-flowing rivers. Once the cycle
of river blindness has been interrupted for 14 years
the reservoir of adult worms dies out in the human population,
thus eliminating the source of the disease.
The parasite reservoir has now virtually died out in
the original 7-country operations area (map) and will
be largely eliminated in the remaining four countries
by the year 2002. To complement vector control activities,
OCP now distributes the drug ivermectin where needed
in the operations area through a community directed
approach. Ivermectin kills the larval worms that cause
blindness and other onchocercal manifestations and acts
to decrease transmission as well.
As a result, a new global
strategy for controlling onchocerciasis has now been
defined that is based on:
yearly administration of single doses of ivermectin
to affected populations.
In
1987 ivermectin's manufacturer, Merck & Co., Inc.,
pledged to provide at no cost all the
drug necessary for as long as necessary to overcome
onchocerciasis as a public health problem. It established
the Mectizan® Donation Program which has collaborated
with WHO, health ministries and non-governmental development
organizations (NGDOs) so that between 1987 and the end
of 1996, more than 65 million doses of Mectizan® had
been donated for distribution.
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Programme
Achievements
At
OCP's launch, more than 1 million people in West Africa
suffered from onchocerciasis, of whom 100 000 had serious
eye problems including 35 000 people who were blind.
Today, the number of infected people within the original
area of operations is practically nil and vector control
efforts have almost ceased.
Some 1.5 million people who were once infected with
onchocerciasis no longer have any trace of the disease.
Eleven million children born in the operational area
since the programme's inception are now free of risk
of contracting the disease.
At the turn of the century it was estimated that OCP
had prevented almost 300 000 cases of blindness in
the 11 countries involved in the programme.
The successful vector control
activities are opening up an estimated 25 million hectares
of fertile riverine land for resettlement and cultivation,
land that was previously deserted for fear of onchocerciasis.
This land has the potential to feed an additional 17
million people annually through the use of indigenous
technologies and farming practices.
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The
African Programme for Onchocerciasis Control (APOC)
The
outstanding success of the Onchocerciasis Control Programme
(OCP), when expressed in health, economic and development
terms, was the motivating rationale for the launching
of a new programme, African Programme for Onchocerciasis
Control (APOC) in December 1995. APOC shares the same
co-sponsoring agencies and donors with the OCP.
Unlike
the OCP, the new Programme, APOC is non-vertical and
based on a full partnership between affected communities,
the participating governments, a consortium of international
non-governmental development organizations (NGDOs) and
bilateral agencies.
The
Programme's objective is to establish, within a period
of 12 years, sustainable community-directed ivermectin
(Mectizan®) distribution systems covering about 50 million
people in 19 countries outside the OCP where onchocerciasis
still is a serious public health problem. These countries
are: Angola, Burundi, Cameroon, Chad, the Central African
Republic (CAR), the Congo, the Democratic Republic of
the Congo, Ethiopia, Equatorial-Guinea, Gabon, Kenya,
Liberia, Malawi, Mozambique, Nigeria, Rwanda, Uganda,
Sudan and Tanzania.
In
these countries, it is estimated that of the 15 million
heavily infected people, 6.4 million live in areas where
the parasite strains are a major cause of blindness
while 8.6 million live in areas where the parasite strains
are responsible for severe skin disease associated with
grave and unrelenting itching.
APOC
partners share responsibilities in implementing the
Programme's principal control strategy which is based
on community directed treatment with ivermectin (CDTI).
Where feasible, ivermectin treatment will be complemented
with vector elimination using environmentally safe methods.
Since
its inception, the Programme management has been set
up at the OCP headquarters and National Onchocerciasis
Task Forces (NOTF) have been created in 14 countries.
The Memorandum (a multilateral agreement) has been signed
by 19 countries and 13 donors bringing the programme
legally into force as of April 1996. At the end of 1999,
12 national plans for the control of onchocerciasis
had been developed and 57 projects were approved for
funding, including: ivermectin distribution projects
(48), vector elimination projects (4) and projects for
strengthening NOTFs' secretariats (5). Thirty-eight
of these projects have already been started.
In
1996, the NGDO Coordination Group facilitated distribution
to 7.5 million people. This number increased to 11.7
million in the first year of APOC's field activities
(1997-1998) and was expected to rise to over 15 million
by the end of 1999. This constant increase, as well
as close working relationships amongst all APOC partners
will enable APOC to achieve its goal of treating about
45 million people by the year 2007.
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Challenges
ahead for OCP and APOC
When
OCP comes to an end in the year 2002, its present strategy
of aerial larviciding will no longer be applicable.
However, some OCP countries are already benefiting from
ivermectin distribution as the only control method.
These will continue with ivermectin treatment, sharing
the same control strategy and challenges with APOC.
The challenges include:
(i)
Developing with the affected communities, competent
delivery systems to serve as example for the delivery
of other drugs to control other tropical diseases.
(ii)
While the OCP towards its end is aiming at having the
devolved activities integrated into the varied health
systems, APOC is aiming at devolving all aspects of
control operations into the health systems from the
onset, in participating countries. The two programmes
will share experiences on this issue.
(iii)
Finally, APOC has an additional challenge, to demonstrate
the effectiveness of its unique partnership in implementing
a sustainable solution to a public health and development
problem.
Source:
WHO
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