Impact sanitaire de l'utilisation d'eaux polluées en agriculture urbaine. Cas du maraîchage à Ouagadougou (Burkina Faso)

In Ouagadougou and in many similar Sahelian cities, urban agriculture uses very often polluted water for irrigation of vegetables, including those that are likely to be eaten uncooked. As the pathogenic germs can survive long enough in water, soil and plants, this practice entails potential sanitary risks, particularly for farmers and their families. The potential of risks related to the use of sewage in agriculture is well known and sanitary instructions exist. However, there is no assessment of real risks within the context of sewage use on a small scale in small size plots, as it is the case in Ouagadougou, and common in Sahelian countries. The aim of the current thesis is to contribute to a better understanding of interactions between the environment and health. The specific objectives are: (i) - to assess incidence rates for diarrhoea In a period of two weeks and to assess prevalence rates for parasitic infections; (ii)- to assess relative risks and prevalence ratios among exposed groups and those of the population in general; (iii) - to assess levels of microbiological pollution of irrigation water, soils and vegetables; (iv) - to assess sociocultural factors and behavioural attitudes of the various actors; (v) - to assess environmental pollution at the level of residential areas; (vi)- to propose possible measures in order to reduce risks and to discuss their feasibility. The general approach that has been adopted is transdisciplinary, particularly with an epidemiological perspective associating microbiology, socio-anthropology, cartography and geomatics. The cartographical approach, with the assistance of geomatics made it possible (i) - to characterize residential areas in Ouagadougou according to pollution by refuse dumps and throwing out of sewage, (ii) - to locate market gardening sites in urban fabric, and (iii)- to assess the importance of exploited surfaces during the dry season, the cool season and the rainy season. Peripheral sectors are more polluted than central sectors. Variation in the total exploited surfaces between the cool season (December) and the dry season (April) is almost 85%. Six areas of market gardening represent in all seasons more than 55% of the total exploited surfaces. The majority of fanners in these 6 areas of market gardening live in 4 to 6 peripheral sectors (79% in 1992, 90% in 1995). The microbiological approach made it possible to monitor bacteriological (fecal coliforms) and parasitological (helminth and protozoan eggs) pollution in water, soils and plants. Water and soil samples have been taken in 4 market gardening areas which represent in all seasons between 49 and 56% of the exploited surfaces in the city; plant samples have been taken in the 4 areas of market gardening and in the central market of Ouagadougou. 668 samples of irrigation water, 247 samples of lettuce, 48 samples of carrots and 218 samples of soils have been analyzed between October 1993 and December 1995. The levels of bacteriological pollution for all types of water, most of the time, are above the thresholds recommended by WHO for the watering of vegetables that are likely to be consumed uncooked (1000 FC/100 ml). Water from canals or channels (Abattoir and Canal Central sites) prove to be more polluted, both bacteriologically and parasitologically, than the one from wells and dams (Boulmiougou and Tanghin sites). Lettuce from both market gardening sites and market has a bacteriological pollution that is beyond sanitary thresholds (100 FC/100 g), with higher levels in the market. A proportion of at least 10% of soil samples from paths are contaminated by parasites such as Ankylostomes, Ascaris and Anguillules. The market gardening sites which have the most polluted beds by parasites are those of Abattoir (79% of samples) and Canal Central (75%) which correspond to the sites with irrigation water that is also the most polluted. The socio-anthropological approach made it possible to gather ideas and beliefs of various actors in the chain of market gardening products (from producer to consumer) and to carry out direct observations about environmental factors as well as about practices in the various places in this chain. During the two years, 15 FGD (Focus Group Discussion) have been held with farmers, retailers, caterers and consumers. In 1995, 226 observations sessions have been held from 22 observation posts (5 market gardening sites, 3 markets, 3 caterers and 11 selected households). Whilst the environmental factors on market gardening sites are characterized by a high level of pollution, the behavioural attitudes of farmers during their activities, particularly walking barefoot, and expressed beliefs reveal a lack of awareness. The epidemiological approach made it possible to assess differences in incidence or prevalence rates between climatic seasons, between farmers and the general population, between market gardening sites, and between sexes, for diarrhoea, stomach aches and various parasitic infections. The data have been collected through households surveys and examinations in analysis laboratories of excreta and of households' drinking water. Three cross-sectional surveys with children as targets have been undertaken in 1994 (2 in the dry season and in the rainy season) and in 1995 (one at the end of the rainy season). Sample sizes were respectively 512, 599 and 3040 children aged between 0 and 4 full years and who have been weaned. During the third cross-sectional survey 208 adults, fathers or mothers of the surveyed children, have been also involved and water samples of 2996 households have been analyzed. A fourth cross-sectional survey dealt only with the group of market gardeners, with 191 adults, 97 children of farmers and 186 samples of households' drinking water. Differences are significant between the end of the rainy season and the two other seasons as far the diarrhoea and the main parasitic infections are concerned among the general population's children aged less than 5 years old. The incidence of two weeks' diarrhoea is very important in all seasons among the children of the general population (always > 30%) as well as among the children of market gardeners at the end of the rainy season (37.10 ± 9.61%). On the other hand, the incidence rate for two weeks' diarrhoea is low among adult farmers themselves at the end of the rainy season (6.30 ± 3.45%). The group of farmers, both children and adults, have in a very significant way higher prevalence rates than those of the general population as far as Ankylostoma are concerned (10.80 ± 6.68% against 1.40 ± 0.43% among children; 40.60 ± 7.38% against 14.90 ± 5.09% among adults). The difference between men and women is very significant for Ankylostoma among market gardeners (48.40% against 30.70%, PR= 1.58, p= 0.03). The epidemiological approach also made it possible to carry out a case-control analysis of diarrhoea among children of the general population aged less than 5 years old. The final logistic regression model draws a significant association (p < 0.05) between children's diarrhoea and 11 risk factors. These factors are related to either habitat conditions, or socio-economic conditions, or behavioural attitudes. The geomatic approach made it possible to disintegrate the main results of the epidemiological approach (as it has been done already for those of the cartographical approach) to present them at the sector level as thematic maps. The study leads to the formulation of recommendations in the area of (i)- actions and interventions; and (ii)- possibilities in research perspectives, regarding health and environment

Improving urban drainage in Abidjan, Côte d’Ivoire

Tropical humid climates of sub-Saharan Africa with a high level of variability build a challenge for hygienic models used in urban drainage. Global models of urban drainage used in this region – for example the Caquot’s rate-of-flow model – are based on the parameters of Montana’s rain model. This model indicates the evolution of the maximum rainfall intensity according to the duration and the return period. In Côte d’Ivoire, several studies highlighted that adapting Montana’s rain model is not satisfactory for particular time slots, which in turn affects urban drainage calculations. This work aims at optimising and designing models which best simulate tropical downpours and improving calculations related to urban drainage in Abidjan and in other urban settings with similar climatic conditions. Various statistical processing undertaken showed that the rainfall distribution in the area of Abidjan is in line with the laws of Gumbel (10 – 30 mn rainfall) and Galton (45 – 240 mn rainfall). Including the data in mathematical conversion formulas made it possible to optimise Montana’s parameters and to design a new model that best simulates downpours in Abidjan. In addition, analysis of the Nicholson index revealed a drop in rainfall in Abidjan with a cyclical evolution ( about 17 year period), alternating dry, normal and wet periods. The new model is relevant since it overlaps two very satisfactory models and could be used to improve urban drainage calculations in Abidjan and similar climatic conditions.Keywords Abidjan; climatic variability; Montana’s model; sub-Saharan African tropical wet region; urban drainag

Variabilité Climatique Et Changements Dans L’environnement À Korhogo En Côte D’ivoire : Mythes Ou Réalité ?

Climate change which is considered as a threat to biodiversity, causes paradoxical situations everywhere it manifests itself. These include, among others, drought and desertification; floods and storms; sea level rise, reduction of the vegetation cover; water supply sources and, animal and plant species disappearance. In Korhogo, in the North of Côte d’Ivoire, the climate variability and environmental change phenomena are perceived and described by the population. A qualitative approach with historical and comparative analysis tools are used in this study to focus on the perceptions of the populations through indicators of both climate variability and environmental changes. It also analyses the major challenges the population will face, which are mainly related to alteration in farming practices and seasons, loss of production, and extension of the lean period, the risk of food insecurity and conflicts related to the exploitation and the distribution of water resources; and mostly, to the lack of information- educationcommunication on the phenomenon. On the whole, although the study brings out an awareness about climate variability and environmental changes, it especially show the need for emergent multidimensional actions for effective response strategies to the changes observed in the area

Analyse de la situation de l’environnement sanitaire des quartiers défavorisés dans le tissu urbain de Yopougon a Abidjan, Côte d’Ivoire

La combinaison, d’informations multi-sources (image QUICKBIRD, données exogènes, résultats d’enquêtes socio-environnementales) dans un système d’information géographique (SIG), a permis d’analyser l'environnement sanitaire de 6 quartiers précaires situés le long d'un canal d'évacuation des eaux à Yopougon, (Abidjan, Côte d’Ivoire). L’analyse et la cartographie des principaux facteurs relatifs à la qualité de vie des populations, permettent de constituer un observatoire de l’environnement sanitaire de ces milieux défavorisés. La finesse spatiale de l’image QUICKBIRD a contribuée à la mise à jour de la carte du mode d’occupation du sol. L’analyse des différents facteurs caractérisant l’environnement sanitaire révèle de nombreuses insuffisances dans le système de gestion de l’assainissement des quartiers précaires, exposant ainsi les populations aux maladies liées à l’assainissement telles que le paludisme et la diarrhée. Les résultats permettront de planifier et de valider les mesures à prendre pour remédier aux déficits d’assainissement dans ces milieux précaires.The integration into a Geographical information system (GIS) of multi-source data from QUICKBIRD imagery, ancilliary data and the results from socio-environmental investigations alowed to analyse the sanitary environment of 6 precarious settlements located along an open and exposed drainage channel, in Yopougon (Abidjan, Côte d’Ivoire). The observatory of the sanitary environment of these deprivileged areas were conducted through analysis and mapping of main factors influencing the life quality of the populations. The spatial sharpness of QUICKBIRD imagery contributed to update the land use/land cover map. Analysis of various factors witch characterise the sanitary environment reveals many insufficiences as regards the management of the sanitation system of the settlements, thus exposing the populations to illness related to sanitation like malaria and diarrhoea. The findings will permit planing appropriate measurements to overcome sanitation problems in these précarious areas

L’étalement urbain au péril des activités agro-pastorales à Abidjan

L’urbanisation rapide, pose des défis de logement et d’alimentation à la communauté internationale dans son ensemble et particulièrement aux pays en voie de développement. A Abidjan en Côte d’Ivoire, le développement de la commune de Yopougon et la croissance démographique de près de 4 %, entrainent une importante pression sur les terres agricoles urbaines et périurbaines. La présente étude met en évidence l’influence de cet étalement urbain sur les activités agro-pastorales à Yopougon. Une démarche cartographique, suivie d’une démarche socio-anthropologique a été adoptée. Des entretiens avec questionnaires ont été effectués avec 93 agriculteurs. Cette étude montre que les activités agricoles se déroulent sur trois principaux sites : Lokoa, Béago et Azito. Entre 2004 et 2007, les sites agricoles ont connu une réduction d’environ 41 % de leurs superficies du fait de la croissance urbaine. La variation totale de superficie due aux constructions est de 40 % à Azito, 18 % à Lokoa et 8 % à Béago. Des parcs à bétails ont changé de position géographique et se retrouvent en bordure de lagune. L’étude montre également que 94 % des agriculteurs du site vivent principalement de l’agriculture urbaine et que l’insécurité foncière reste leur principale préoccupation. L’étalement spatial de la commune de Yopougon, contribue à une forte réduction des superficies agricoles rendant ainsi vulnérable les familles impliquées dans les activités agricoles comme principales sources de revenus.Rapid urbanization leads to challenges in housing and food access for all the international community and particularly in developing countries. In Abidjan, the developments of Yopougon municipality and population increase have caused significant pressure on agricultural lands and represent a danger for agriculture in the surrounding villages. The present study aims at highlighting the influence of urban spread on agro-pastoral activities in the district of Yopougon. A cartographic approach and a socio anthropologic approach were used. Observations and individual interviews were made with 93 agricultural actors. Agricultural activities were observed on three principal sites : Lokoa, Béago and Azito. Between 2004 and 2007, approximately 41 % of the agricultural surface was occupied by settlements. Total variation of surface due to settlements was 40 % at Azito, 18 % at Lokoa and 8 % at Béago. Some pastoral and cattle parks were joined by the city and were moved to other geographical positions. For 94 % of agricultural actors in the studied site, agriculture was the principal source of income and land insecurity remained the principal concern of the farmers. The urban sprawl of the municipality of Yopougon contributes to a strong reduction of agricultural surface. It makes agricultural actors vulnerable as it is their only source of income

Nutritional and health status of children 15 months after integrated school garden, nutrition, and water, sanitation and hygiene interventions: a cluster-randomised controlled trial in Nepal

It has been suggested that specific interventions delivered through the education sector in low- and middle-income countries might improve children's health and wellbeing. This cluster-randomised controlled trial aimed to evaluate the effects of a school garden programme and complementary nutrition, and water, sanitation and hygiene (WASH) interventions on children's health and nutritional status in two districts of Nepal.; The trial included 682 children aged 8-17 years from 12 schools. The schools were randomly allocated to one of three interventions: (a) school garden programme (SG; 4 schools, n = 172 children); (b) school garden programme with complementary WASH, health and nutrition interventions (SG+; 4 schools, n = 197 children); and (c) no specific intervention (control; 4 schools, n = 313 children). The same field and laboratory procedures were employed at the baseline (March 2015) and end-line (June 2016) surveys. Questionnaires were administered to evaluate WASH conditions at schools and households. Water quality was assessed using a Delagua kit. Dietary intake was determined using food frequency and 24-h recall questionnaire. Haemoglobin levels were measured using HemoCue digital device and used as a proxy for anaemia. Stool samples were subjected to a suite of copro-microscopic diagnostic methods for detection of intestinal protozoa and helminths. The changes in key indicators between the baseline and end-line surveys were analysed by mixed logistic and linear regression models.; Stunting was slightly lowered in SG+ (19.9 to 18.3%; p = 0.92) and in the control (19.7 to 18.9%). Anaemia slightly decreased in SG+ (33.0 to 32.0%; p < 0.01) and markedly increased in the control (22.7 to 41.3%; p < 0.01), a minor decline was found in the control (43.9 to 42.4%). Handwashing with soap before eating strongly increased in SG+ (from 74.1 to 96.9%; p = 0.01, compared to control where only a slight increase was observed from 78.0 to 84.0%). A similar observation was made for handwashing after defecation (increase from 77.2 to 99.0% in SG+ versus 78.0 to 91.9% in control, p = 0.15).; An integrated intervention consisting of school garden, WASH, nutrition and health components (SG+) increased children's fruit and vegetable consumption, decreased intestinal parasitic infections and improved hygiene behaviours.; ISRCTN17968589 (date assigned: 17 July 2015)

Bayesian conditional autoregressive models to assess spatial patterns of diarrhoea risk among children under the age of 5 years in Mbour, Senegal

Diarrhoeal diseases remain a major public health problem, causing more than half a million child deaths every year, particularly in low- and middle-income countries (LMICs). Despite existing knowledge on the aetiologies and causes of diarrhoeal diseases, relatively little is known about its spatial patterns in LMICs, including Senegal. In the present study, data from a cross-sectional survey carried out in 2016 were analysed to describe the spatial pattern of diarrhoeal prevalence in children under the age of 5 years in the secondary city of Mbour in the south-western part of Senegal. Bayesian conditional autoregressive (CAR) models with spatially varying coefficients were employed to determine the effect of sociodemographic, economic and climate parameters on diarrhoeal prevalence. We observed substantial spatial heterogeneities in diarrhoea prevalence. Risk maps, stratified by age group, showed that diarrhoeal prevalence was higher in children aged 25-59 months compared to their younger counterparts with the highest risk observed in the north and south peripheral neighbourhoods, especially in Grand Mbour, Médine, Liberté and Zone Sonatel. The posterior relative risk estimate obtained from the Bayesian CAR model indicated that a unit increase in the proportion of people with untreated stored drinking water was associated with a 29% higher risk of diarrhoea. A unit increase in rainfall was also associated with an increase in diarrhoea risk. Our findings suggest that public health officials should integrate disease mapping and cluster analyses and consider the varying effects of sociodemographic factors in developing and implementing areaspecific interventions for reducing diarrhoea

Disease burden due to gastrointestinal infections among people living along the major wastewater system in Hanoi, Vietnam

Background : Despite recent improvements of wastewater treatment capacities in urban areas of Hanoi, Vietnam, microbial pollution is still considerable. There is a paucity of burden estimates due to gastrointestinal infection in people living along the wastewater system, and among people who are in direct contact with the wastewater, such as farmers using wastewater in agriculture and aquaculture. Methods : A quantitative microbial risk assessment (QMRA) was pursued focussing on four population groups characterised by different levels of exposure to wastewater: (i) workers maintaining the wastewater conveyance and treatment systems; (ii) urban farmers using wastewater from To Lich River; (iii) community members in urban areas exposed to flooding events in the districts of Hoang Mai and Thanh Tri; and (iv) peri-urban farmers in Thanh Tri district, where Red River water is used for agriculture and aquaculture. The QMRA was developed on the basis of measured concentration of Escherichia coli and Salmonella spp. and Ascaris spp. eggs in water samples. Published ratios between measured organisms and pathogenic strains of norovirus, rotavirus, Campylobacter spp., pathogenic E. coli, pathogenic Salmonella spp., Cryptosporidium spp. and Ascaris lumbricoides were employed to estimate annual risk of gastrointestinal infection and disease burden. Results : The QMRA estimated a disease burden of 0.011 disability-adjusted life years (DALYs) per person per year in urban farmers, 0.006 DALYs for sanitation workers, 0.0005 DALYs for urban communities at risk of flooding events and 0.0004 DALYs for peri-urban farmers. Urban farmers had considerably higher incidence estimates for gastrointestinal disease episodes per year (2.0) compared to the other exposure groups (≤1.0). Conclusions : Urban farmers using wastewater from To Lich River have a high gastrointestinal disease burden, which is about 100 times larger than the health-based targets for wastewater use set by the World Health Organization. These findings are of direct public health relevance and call for upgrading Hanoi's wastewater system to reduce microbial contamination. Finally, this study presents a first example on how to link QMRA to a sanitation safety planning (SSP) approach in an Asian context and its findings are interesting in the frame of Sustainable Development Goal (SDGs) #6

Prevalence of intestinal parasitic infections and associated risk factors among schoolchildren in the Plateau Central and Centre-Ouest regions of Burkina Faso

BACKGROUND: Unsafe drinking water, unimproved sanitation and lack of hygiene pose health risks, particularly to children in low- and middle-income countries. This study aimed to assess the prevalence and risk factors of intestinal parasitic infections in school-aged children in two regions of Burkina Faso. METHODS: A cross-sectional survey was carried out in February 2015 with 385 children aged 8-14 years from eight randomly selected schools in the Plateau Central and Centre-Ouest regions of Burkina Faso. Stool samples were subjected to the Kato-Katz and a formalin-ether concentration method for the diagnosis of helminths and intestinal protozoa infections. Urine samples were examined with a urine filtration technique for Schistosoma haematobium eggs. Water samples from community sources (n = 37), children's households (n = 95) and children's drinking water cups (n = 113) were analysed for contamination with coliform bacteria and faecal streptococci. Data on individual and family-level risk factors were obtained using a questionnaire. Mixed logistic regression models were employed to determine factors associated with intestinal parasitic infections in schoolchildren. RESULTS: Intestinal parasitic infections were highly prevalent; 84.7 % of the children harboured intestinal protozoa, while helminth infections were diagnosed in 10.7 % of the children. We found significantly lower odds of pathogenic intestinal protozoa infection (Entamoeba histolytica/E. dispar and Giardia intestinalis) among children from the Plateau Central, compared to the Centre-Ouest region (P < 0.001). Children from households with "freely roaming domestic animals" (P = 0.008), particularly dogs (P = 0.016) showed higher odds of G. intestinalis, and children reporting exposure to freshwater sources through domestic chores had higher odds of S. haematobium infection compared to children without this water contact activity (P = 0.035). Water quality, household drinking water source and storage did not emerge as significant risk factors for intestinal parasitic infections in children. CONCLUSIONS: Intestinal protozoa but not helminths were highly prevalent among schoolchildren in randomly selected schools in two regions of Burkina Faso. Our findings call for specific public health measures tailored to school-aged children and rural communities in this part of Burkina Faso. It will be interesting to assess the effect of water, sanitation and hygiene interventions on the transmission of intestinal parasitic infections