Case of Sourou in Burkia Faso
D. Dianou, PhD
J. N. Poda, PhD
H. Sorgho, PhD student
S. P. Wango, PhD student
K. B. Sondo, Pr, MD, PhD
Department of Biomedical and Public Health
IRSS/CNRST, B.P. 7047, Ouagadougou,
KEY WORDS: Burkina Faso,
Sourou, water-related schistosomiasis, prevalences
The population of Burkina
Faso would like to have dams constructed
because of a lack of water for people and animal alimentation, and for
irrigation and pisciculture. The satisfaction provided by the proximity
of a dam is sufficiently felt by the populations from all over Burkina
Faso. Today, the small dams and their
hydroagricultural management, which are often associated, form more
parts of the Burkinabe landscapes.
Unfortunately, the dams support the installation of molluscs,
which often cause schistosomiasis. The extension of schistosomiasis
depends on the importance of parasite exchange between people and the
To support the hydroagricultural projects for an integral
approach to managing water resources by the schistosomiasis program,
it is important to evaluate the extent of the problem. Therefore, parasitologic
surveys in schools and malacologic investigations
on the transmission sites were carried out in the Sourou region.
The results obtained showed a gradual increase in the
prevalence of urinary bilharziasis in Guiedougou with 19%, 23%, and
70% in 1954, 1987, and 1999, respectively. The prevalences recorded
in 1999 were 40.8% and 8.5% in Niassan and Debe, and 55.6% and 56.8%
in the traditional villages of Lanfiera and Di, respectively. As for
the intestinal bilharziasis, absent until 1987 when 3 cases were detected
among migrants, prevalence ranged from 8% to 69% in 1999 in the villages
located along the irrigation zone. Concerning the malacologic investigation,
2 species (Bulinus senegalensis and Bulinus truncatus) were identified
as intermediate hosts of Schistosoma haematobium. Bulinus senagalensis
was found naturally infested, whereas Bulinus truncatus was compatible
with S. haematobium from the Sourou and other zones. Biomphalaria pfeifferi
was shown to be an intermediate host of Schistosoma mansoni.
Hydraulic plannings constitute amplifying factors for
the proliferation of mollusc species and parasite exchange. Everyone
(scientists, developers, and populations) is challenged to attenuate
or reduce the development of schistosomiasis, which reduces the benefit
gained from hydroagricultural plannings.
The accelerated precariousness of vegetable and animal
production conditions is often the image that prevails in Sub-Saharan
Africa. Populations facing this hostility of nature have for a long
time adopted traditional strategies of water and soil conservation or
have decided to migrate. Thus, hydraulic plannings, especially dams,
as an anthropic action on natural environments, often associated with
environmental and sanitary risks, appear to be an alternative to climatic
uncertainties and demographic pressure.
Because of these conditions, dams and hydroagricultural
plannings have existed for many years; therefore, a focus on privileged
development to face the decrease in food availability per capita is
also related to an increase in population. However, these strategies
should not hide the numerous sanitary problems that could be associated
with water management.
Among the parasite
infections, water-dependent schistosomiasis (bilharziasis) appears to
be particularly sensitive to the modifications of the relations between
the human community and the aquatic environment, because one of the
characteristic features is their ability to get used to and benefit
from the transformations related to hydroagricultural management. The
human forms of schistosomiasis represent the world's second leading
endemic disease after malaria, and affects 200 million people in 74
countries.1 As a risk in daily and professional life, as a beneficiary
of these projects, schistosomiasis comes to the forefront with regard
to the prevalence of diseases related to hydrous transmission.2 The
harmonization of the efforts in the control of schistosomiasis since
site management to the selection of measures able to reduce the durability
of the bilharzian risk, it is likely to induce a better comprehension
of mechanisms guiding and connecting the various processes in a given
The Sourou region provides an opportunity for a comparative
study of the juxtaposition of strongly framed spaces of different ages
intended for the irrigated cultures, and the traditional villages that
undergo the effects of irrigation. This study illustrates the situations
in which the people and their environment are brutally transformed.
MATERIAL AND METHODS
Description of the Sites Studied
(Fig. 1) was an affluent tributary of the Mouhoun
River until the construction
of the Lery Dam in 1976. In 1985, the installation of a foundation raft
on the Mouhoun River
and the opening of a canal led to the transit of water of Mouhoun coming
from the western south toward the Sourou. Thus, this installation allows
the mobilization of a great quantity of water throughout the Sourou
region for the irrigation of cultures. Therefore, between the traditional
villages of Lanfiera and Di large cooperatives were progressively established
nexing the irrigated perimeters at Guiedougou, Niassan, and Debe in
1967, 1986, and 1996, respectively, with the installation of producers
coming from different regions of the country.
The region of Sourou
(Fig. 2) is characterized by a north-Soudanian climate with a rainfall
inferior to 900 mm. The surface water resources are represented by the
Mouhoun, the reserve of Sourou, which temporarily feeds the irrigation
canals and the ponds.
Parasitologic and Malacologic
The parasitologic investigations were carried out on school-aged
children using the technique of parasite concentration in Merthiolate-Iodure-Formol
(MIF) and reactive strips to evaluate the prevalence rates of S. mansoni
and S. haematobium. The methods of urine filtration and Kato Katz for
stool observation were used to evaluate the parasitic load. All the
children found positive were treated with Praziquantel (40 mg per kilogram
of body weight). The levels of prevalence are considered hypoendemic
below 25%, mesoendemic between 25% and 50%, and hyperendemic over 50%.
On each site, the research on molluscs was carried out
on support in water. Molluscs were identified by the examination of
the shell. The sites in which one or several
mollusc intermediate hosts were collected, at least once within 30 minutes
of inspection, are regarded as positive. To evaluate the natural infestation
in the laboratory, each alive mollusc was placed in a pill machine containing
drilling water and exposed to an artificial source of light (36-W neon),
which leads to the release of parasites of schistosomes from the infested
RESULTS AND DISCUSSION
The results obtained were related to the following 2 known
and widespread forms of schistosomiasis in Burkina
Faso: Schistosoma mansoni, responsible
for intestinal bilharziasis, and S. haematobium, leading to urinary
The parasitologic results on S. haematobium are presented
on Table 1. As for S. mansoni, which was absent in the zone until 1987
when 3 isolated cases were observed among migrants in Niassan, the prevalence
in 1999 fluctuated from 8% to 69% in the villages located along the
managed zones and in the small islands surrounded by the hydraulic plannings,
including 50.6% of Toma island. Regarding the contamination points,
the major part of the aquatic systems of planned zones lodge during
one of the favorable periods (fresh or rainy season) several intermediate
hosts of human schistosomiasis. The species collected and identified
are Biomphalaria pfeifferi for intestinal schistosomiasis and the genus
Bulinus for urinary schistosomiasis (Table 1).
In Burkina Faso,
the first dams were built in approximately 1920, mostly by the Catholic
missionaries to stabilize populations in their center by offering less
precarious living conditions. These initiatives, strengthened
by those of the colonial administration who were permitted to build
before 1960 more than 100 dams for human and livestock water supply.
From 1960, programs of small ground dams were successively scheduled
with some hydroagricultural plannings downstream. The number of dams
increased, especially in the regions of the central plateau, where henceforth,
they are included in the Burkinabe landscape.
authorities registered 714 and 1078 dams and water reserves in 1987
and 1990, respectively. The construction of the Kompienga and Bagre
Dams inaugurated the era of hydroelectric dams with some hydroagricultural
plannings in Bagre to face the stress of the food and energy crisis.
Insofar as the dams exist, and will continue to develop, it appears
essential to take into consideration the fact that they create a broad
range of biotopes of the human bilharziasis intermediate hosts, and
that they are the sites of parasitic flux, which is related to their
In the zone of Sourou, urinary schistosomiasis was underlined
before our study. In 1954, the results of parasitologic investigations
showed a total prevalence of 19% in school-aged children.3 In 1987,
the investigation carried out in Niassan by the structures of the Ministry
of Health at the request of the Authority of the Sourou Valley (AMVS)
revealed a prevalence of 32% in the indigenous population, 23% in school
children, and 6% in the migrant population for S. haematobium and 3
isolated cases for S. mansoni. The investigations by Kabore4 on 15-year-old
children in the traditional village
of Yaho showed a mixed schistosomiasis
infestation with prevalences of 55.29% for S. haematobium and 69.3%
for S. mansoni. In 1999, our study showed a prevalence of 50.6% for
S. mansoni in Toma-île village.
The results of the parasitologic investigations (Table
1) showed that all the villages studied are the seat of bilharziasis
infestation with, however, some disparities related to the intensity
of the endemic disease. As for the differences in prevalences, the geographic
situation, the age of the installation of the irrigated sites, the proximity
of aquatic systems near children, and their parent activities could
be factors responsible for these disparities. Indeed, the schistosomiasis
prevalences recorded in Guiedougou, Niassan, and Debe seem to be in
close relation with the age of the hydroagricultural plannings, which
are 35, 16, and 6 years, respectively. The traditional villages of Lanfiera
and Di, surrounded by the installations, undergo their amplifying effects.
One could think that the proximity of the villages compared with the
reserve of water and the canals supports the earlier and repeated contacts
of man and water from children who additionally join with the activities
of their comrades in the planning zones.5
the malacologic level, Sellin et al.6 indicated
the presence of B. truncatus, B. forskalii, and B. senagalensis in the
Sourou region; on the other hand, Biomphalaria pfeifferi was not identified.
Our results confirmed the results obtained by these authors. The apparition
of Biomphalaria pfeifferi could be related to the installation of the
canal connecting the Mouhoun
River branch coming from
the region of Bobo (zone of high density of B. pfeifferi) with the Sourou
in 1984. B. senagalensis seems pledged to the temporary ponds often
located near the dwellings. The natural infestation test with B. senagalensis
and the test of compatibility with B. truncatus showed that the 2 species
are responsible for S. haematobium transmission in the zone of Sourou.
B. truncatus could be more sensitive to the strains of parasites issued
from the other regions.
The same feature is prevailing in the Kou Valley, the
first irrigated perimeter of Burkina Faso planned in 1967 in which the
schistosomiasis prevalences have been increasing from 14% in 19577 to
80% in 1987 for S. haematobium and from 1.3% to 45% for S. mansoni in
the same period. The same tendencies were observed in Bagre (Fig. 2)
planned in 1995, in which the prevalences of the 2 forms of schistosomiasis
are increasing in relation to the hydroagricultural activities. The
great water stretches of Ziga Dam built in 1999 and the one of Kompienga
built in 1997, even in the absence of irrigation, could induce a rise
in the prevalences currently observed (19.3% for S. haematobium, 0%
for S. mansoni in Ziga, and 16.3% for S. haematobium, <0.5% for S.
mansoni) in Kompienga.
The distribution of schistosomiasis in populations of
hydroagricultural plannings is traditional, and school-aged boys are
particularly concerned. The average prevalence is largely over the national
one, which is approximately 30%,8 with disparities
related to the site. The characteristics of the hydraulic plannings
are the result of the following major points.
The first observation is that the hydraulic plannings
join together several types of biotopes at the same place. Thus, they
are side-by-side aquatic systems of stagnant, running, and temporary
water. The investigations on different biotopes showed that the radical
change of aquatic environment by water stagnation in the form of dams
is the basis of malacologic fauna proliferation,
especially B. truncatus.9 B. senagalensis is pledged to the temporary
aquatic systems. As for B. globosus and B. pfeifferi, which are supported
by the permanence of a diffuse water flow, they appear as the species
of the irrigated sites. Therefore, the hydraulic plannings support the
coexistence of several intermediate hosts at different periods, which
mostly is a sufficient condition for the development of schistosomiasis.
The second observation is the result of the fact that
the spectrum of potential intermediate hosts of schistosomiasis is limited
to some strains of parasites.10 This compatibility is only the expression
of the genetic variability of the intermediate host confronted to the
genetic variability of the parasite, and is defined by the similarity
in genomes between a host and a parasite.11 Hydroagricultural planning,
in addition to the increase in density and diversity of mollusc species,
supports the transfer of several strains of parasites with the recruitment
of new agricultural workers issued from different regions of the country.
Thus, this situation leads to intense parasite fluxes between the hosts
(intermediate and/or definitive) and the different strains of parasites.
This phenomenon constitutes one of the essential elements for the amplification
of the prevalences recorded.
third observation is that the hydroagricultural plannings create the
frameworks of new activities related to water, allowing not only the
maintenance of zones with high endemicity, but also an extension of
the parasite infections to healthy or weakly infested zones. Indeed,
the endemicity levels vary in relation to the level of initial endemic
disease, the distance between the location of dwellings, the places
of potential transmissions, and the sociologic phenomena which bind
people with the places of contamination.12 Thus, by the fact that they
offer favorable conditions through the contact of people with contaminated
water, hydraulic plannings constitute a factor of contamination intensification.
Taking into consideration these observations, schistosomiasis
appears as an affection particularly sensitive
to the modifications of relations between the human community and the
aquatic environment. That is linked to the fact that the concomitant
increase in hydrous surfaces and human densities supported by the hydraulic
plannings leads to a multiplication of the interfaces of people and
water favorable to bilharziasis parasites, whose cycle is closely related
to the human-water relation.
The dams cannot be overlooked to meet the needs of water
alimentation for man and cattle, for alimentation, and recently for
energy production. Insofar as they exist, and will continue to develop
as new poles of development related to water in Burkina
Faso, it appears essential to take
into account that they create a broad range of biotopes, crossroads
of biologic diversities among which are the molluscs, intermediate hosts
of schistosomiasis. Therefore, it will be necessary to reconcile water
resource management with health promotion.
In 1984 the Committee
of the World Health Organization (WHO) experts adopted a strategy to
face schistosomiasis.13 The recent report of the WHO abstract consultation
on the matter stressed the fight against the morbidity of schistosomiasis
by chemotherapy with praziquantel in addition to the fight against molluscs,
the supply of drinking water, and the equipment of sanitary structures.14
The progress in sciences and technology on hydraulic planning proved
to be able to plan, conceive, build, and exploit dams with a minimum
of unforeseen or unacceptable impact. However, the objective is to put
into balance the negative-induced impact with the benefits anticipated
from the hydraulic plannings. The World Health Organization described
the extent of the problem and developed the policies for a better public
health policy to be conducted regarding the consequences.15 In 1982,
the International Association of Limnology, with the support of the
Program for Environment of the United Nations (PNUE), recommended that
a certain percentage (0.1% or more) of the total cost of dam realization
should be reserved to finance research to solve problems created by
This work was funded by the AUF (JER 305 research team)
and AIRE développement (convention 01-3-BF-22-1 with the research team
"Scistosomoses en Orbite") to which the authors are grateful.
The Authority of the Sourou Valley (AMVS), the staff of
the medical centers of Tougan, Lanfiera, Di, and the populations of
the sites studied are acknowledged.
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of the study area.
of the main hydraulic plannings in Burkina
Table 1. Intermediate Hosts and Prevalences of
Schistosoma haematobium in Sourou, Burkina Faso
Site Biotope Mollusc
Guiedougou Ponds, canals B.
Niassan Canals B. senegalensis 40.8
Debe Canals B. senegalensis 8.5
Lanfiera Ponds, canals B.
Di Ponds, dams B.