Scientific bulletin 324 - July 2009
Onchocercosis, or “river epilepsy”
© IRD / Michel Boussinesq
of social exclusion
and deep distress.
Their plight is even
more painful in Africa:
discriminating beliefs
and deficiencies of
access to treatments
bring about an
excessively high
death rate. Developing
countries, including
in Africa, are home
to around 90% of all
epileptics. This is a huge
proportion compared
with the countries of
the North. What is the
explanation for this?
In the tropics, epileptic
fits are often triggered
by neurological
consequences of various
endemic diseases,
such as malaria. IRD
scientists and their
research partners1
recently showed that
another parasitic
infection widespread
in Sub-Saharan Africa,
onchocerciasis, could
also be a cause of
epilepsy. Results from
eight studies conducted
in West, Central and East
Africa showed that apart
from the usual effects
on the skin, and in the
eyes which earns it the
name “river blindness”,
onchocerciasis is
associated with a marked
increase in epilepsy. The
disease could thus just
as well be called
“river epilepsy”.
© IRD / Henri Guillaume
ifty million epilepsy
F
sufferers the world
over carry the burden
A village in Guinea abandoned to escape from onchocerciasis.
Inset: A Cameroon woman hit by “river blindness”, or onchocerciasis. Apart from severe eye
damage, the disease can also bring on epilepsy.
Onchocerciasis, a parasitic disease
highly widespread in tropical Africa,
generally known as “river blindness”,
could also be a cause of epilepsy. That
is the conclusion of a far-ranging analysis run by IRD researchers and their
partners1 on epidemiological data collected in seven African countries.
Epileptic seizures are induced by a
sudden excessively strong electrical
discharge in certain areas of the brain,
following a transient malfunction. The
causes and factors behind the disease
are often undetermined. Epilepsy hits
50 million people in the world, 90% of
whom live in developing countries. In
Africa, the prevalence rates are far
higher than those in the countries
of the North, owing particularly to
the heightened risk from endemic
infections that leave neurological
consequences, such as malaria or, as
the research team recently found, onchocerciasis.
Two closely associated diseases
In a given community, the proportion
of people afflicted with epilepsy was
strongly correlated with the frequency
of onchocerciasis in the population. A
10% increase in the latter disease (as
high as 90% in some regions) was accompanied by an average 0.4% rise
in the epilepsy prevalence rate. This
conclusion was drawn after a statistical
review and analysis of all the existing
literature on the subject, the equivalent
of 12 000 persons examined for onchocerciasis and nearly 80 000 for epilepsy. Seven countries, all African, had
previously been included in studies on
the relation between the two pathologies: Cameroon, Nigeria, Uganda, Burundi, Central African Republic, Tanzania and Benin. The team then showed
the close link that exists between the
two diseases.
Onchocerciasis a cause of epilepsy?
Why has a person infected with onchocerciasis a higher risk of becoming
epileptic ? Onchocerciasis is caused
by the parasitic filarial worm Onchocerca volvulus, transmitted to humans
by black fly, Simuliidae, which reproduce in rivers and streams. The worms
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live for 12 to 15 years in subcutaneous
nodules and produce thousands of larMichel BOUSSINESQ,
vae, or microfilariae, which spread in
director of research at IRD
the skin and into the eye. The immunoUMR VIH/SIDA
logical response against these microfiet maladies associées
(IRD, Université Montpellier 1) lariae induces sometimes unbearable
itching, severe skin rashes and spots
Address:
and in particular some serious eye
Centre IRD de Montpellier
damage including inflammation and
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sclerosing. Onchocerciasis is indeed
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the world’s second cause of infection34294 Montpellier Cedex 5
induced blindness. Strong infestations
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can lead to the presence of microfilamichel.boussinesq@ird.fr
riae in the blood, urine and cerebrospinal fluid. It is therefore possible that
Sébastien PION,
they also penetrate the brain tissue,
researcher at IRD
leading to cerebral irritation, and hence
UMR VIH/SIDA
bouts of epilepsy.
et maladies associées
(IRD, Université Montpellier 1) Epilepsy behind fatal accidents
Epilepsy is a disease which is often
Address:
disregarded and misunderstood. It is
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highly stigmatized owing to sometimes
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dramatic external effects – including
34294 Montpellier Cedex 5
loss of consciousness, convulsions,
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foaming at the mouth or tongue biting.
More particularly in some regions of
sebastien.pion@ird.fr
Africa, where it is considered, wrongly,
REFERENCES:
as contagious through possible contact
with saliva ejected during an attack.
Pion S., Kaiser C., BoutrosA person affected cannot be touched,
Toni F., Cournil A., Taylor
M.M., Meredith S.E.O., Stufe
and cannot therefore be rescued if
A., Bertocchi I., Kipp W.,
he or she falls into water or a kitchen
Preux P.-M., Boussinesq M.
fire for example. Thus, on top of the
Epilepsy in Onchocerciasis pathological consequences, this neuEndemic Areas: Systematic rological disorder increases the risk
Review and Meta-analysis of
Population-Based Surveys. of premature death. Drownings and
severe burns are some of the signifiPlos Neglected tropical
cant causes of excessive mortality in
diseases, 3(6), p. 9-10, 2009
African patients. The IRD researchers
had shown in a previous investigation
in Cameroon that an epileptic’s life
expectancy was very much reduced.
Moreover, the disease leads to social
exclusion and discrimination. Epileptics
hence leave school much earlier, experience difficulty in finding a spouse and
have fewer children than the rest of
the population. This observation takes
on an even more bitter aspect in the
knowledge that epilepsy attacks can
be prevented if the patient follows an
appropriate antiepileptic treatment. Unfortunately, these medicines are often
scarcely available or financially inaccessible for the poorest communities.
Onchocerciasis has been the target
of a strong wide-ranging control programme since 1995. Over 60 million
people are currently treated every
year. The link with epilepsy that has
been detected should encourage the
international community to continue
its efforts.
CONTACTS:
Gaëlle Courcoux - DIC
Translation - Nicholas Flay
1. This research work was conducted in
conjunction with researchers from: the Basic
Health Services Kabarole & Bundbugyo District at Fort Portal in Uganda; the Faculté de
Médecine, Limoges; Arizona Department of
Health Services in Phoenix, USA; Peramiho
Mission Hospital in Tanzania; the Diocèse de
Bouar in Central African Republic; the University of Alberta in Canada.
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© IRD / Henri Guillaume
KEY WORDS:
Onchocerciasis, epilepsy,
Africa
© IRD /Henri Guillaume
Scientific bulletin 324 - July 2009
For further information
A man in Burkina Faso with severe eye damage
caused by onchocerciasis.
Rivers, like this one in Guinea, are breeding
grounds for black fly, Simulium spp., which
transmit the onchocerciasis parasite to humans.
Gaëlle Courcoux, coordinator
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