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Hydraulic Plannings
and Schistosomiasis:
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,
KEY WORDS:
ABSTRACT
The population of
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 intermediate hosts.
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.
INTRODUCTION
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
environment.
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
Sourou
(Fig. 1) was an affluent tributary of the
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
Data-Gathering
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
molluscs.
RESULTS AND DISCUSSION
The results obtained were related to the following 2 known
and widespread forms of schistosomiasis in
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
The 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 fast extension.
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
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
At
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
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.
The 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.
CONCLUSION
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
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
dam planning.9
Acknowledgments
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.
REFERENCES
1. OMS: Impact de la schistosomiase sur la santé publique: morbité et mortalité. Bull OMS 72:5-11, 1994.
2.
Doumenge JP, Mott KE, Cheung C, et al: Atlas de la répartition
mondiale des schistosomiases.
3. McMullen DB, Francotte J: Report on a preliminary survey by the WHO Bilharziasis Advisory team. Part III Upper-Volta. WHO/Pa/78.61; 1960:3-46.
4.
Kaboré A: Investigation étiologique d'une mortalité juvénile
élevée dans le village de Yayo (
5. Takougang I, Louis JP, Migliani R, Noumi E, Mohome N, Same-Ekoko A: Quelques aspects comportementaux de l'exposition à la bilharziose dans les aménagements hydro-agricoles en zone sahélienne (extrême nord Cameroun). Cahier Santé 3:457-463, 1993.
6. Sellin B, Simonkovich E, Diarassouba Z: Mollusques hôtes intermédiaires des schistosomiases dans le secteur de Dori, Kaya, Ouahigouya et Dédougou (Haute volta). Doc Tech OCCGE, N 7357; 1980.
7. Sansarricq H: La bilharziose à Schistosoma haematobium en Haute Volta dans la région de Bobo-Dioulasso. Med Trop 19:345-349, 1959.
8.
Brasseur P, Druilhe P: Dispersion géographique de l'endémie bilharzienne
dans trois départements du
9. Symoens JJ, Burgis M, Gaudet JJ: Ecologie et utilisation des eaux continentales africaines. Ser tech PNUE (1); 1982.
10. Combes C: La spécificité des schistosomes: deuxième
symposium sur la spécificité parasitaire des parasites de vertébrés.
11. Basch PF: An interpretation of snail-trematode infection rates: Specificity in based on concordance of compatible phenotype. International Journal of Parasitology 5:449-452, 1975.
12.
Sellin B, Rey JL, Simonkovich E, Sellin E, Mouchet F: Essai de
lutte par chimiothérapie contre Schistosoma haematobium en zone irriguée
sahélienne au
13. OMS: Lutte contre la schistosomiase. Ser rap tech N 728; 1985.
14. OMS: Rapport de la consultation informelle de l'OMS sur la lutte contre la schistosomiase. WHO/CDS/SIP/99; 1998.
15.
OMS: Atélier sur le rôle des contacts homme/eau dans la transmission
de la schistosomiase. IDR/SER-HWC/79.3; 1979.
Figure 1.
Location
of the study area.
Figure 2.
Location
of the main hydraulic plannings in
Table 1. Intermediate Hosts and Prevalences of
Schistosoma haematobium in
Prevalenceof
Site Biotope Mollusc
S. haematobium
Guiedougou Ponds, canals B.
Senegalensis 70.3
B. truncatus
Niassan Canals B. senegalensis 40.8
B. truncatus
Debe Canals B. senegalensis 8.5
B. truncatus
Lanfiera Ponds, canals B.
senegalensis 55.6
B. truncatus
Di Ponds, dams B.
senegalensis 56.8
B. truncatus
ISSN# 1542-2666