Clinical and microbiological assessment of trachoma in the kolofata health district, far north region, cameroon

Background and aims: Trachoma is a sight-threatening process triggered by the infection of the conjunctiva with Chlamydiae. Blindness associated with trachoma was reported in Sahelian areas of Cameroon. However, data on the prevalence of this neglected infection in the Far North Region are not available. The aim of this study was a) to assess clinical trachoma and b) to detect Chlamydia in the conjunctiva of trachomatous populations living in the Far North Regions of Cameroon.Methods: A total of 2,423 randomly selected children (1–10 years) and 1,590 women over 14 from randomly selected villages from the Kolofata Health District (115,000 inhabitants) were included in a cross-sectional study in February 2009. Trained staff examined and obtained conjunctival swabs from trachomatous subjects. DNA was extracted and amplified to detect Chlamydia DNA by real-time PCR. The quality of sampling was assessed by quantifying the number of epithelial cells.Results: Children (2,397 or 98.9% of the predicted number) and women (1,543; 97.0%) were examined. The prevalence of follicular trachoma (TF) in children was 21% (95% CI 17.8–24.5) and of intense inflammatory trachoma (TI) 5.2% (95% CI 3.6–7.3). Among the women, trichiasis (TT) was observed in 3.4% (95% CI 2.4–4.7), corneal opacities (CO) in 1.4% (95% CI 0.8–2.3) and trachoma-related blindness in 0.9% (95% CI 0.4–1.8). Conditions related to income, illiteracy, latrines, water supply and animals wandering close to dwellings were similar in all the villages. PCR was positive in 35% of children with active trachoma and in 6% of adult females presenting TT and/or related corneal opacities.Conclusion: The prevalence of trachoma and the severe trachoma sequelae found during this survey underline the urgent need to implement efficient blindness prevention interventions to improve the visual future of the people in the Sahelian region.     

La santé des pasteurs mobiles au Sahel – Bilan de 15 années de recherches et développement

Dans le Sahel, entre la Mauritanie et la Somalie incluant le Nord Kenya, environ 20 à 30 millions de personnes vivent en transhumance. Le rythme de leur migration suit l’évolution saisonnière du climat et la disponibilité des ressources, telle que l'eau, le pâturage et le sel. Malgré une exposition élevée à certaines maladies comme les zoonoses et les problèmes conditionnés liés au climat, les pasteurs mobiles sont parmi les populations quasiment exclues du système de santé, car la mise à disposition des services sociaux adaptés à un mode de vie mobile est difficile. Suivant l'objectif de recherche d'un meilleur accès aux soins des pasteurs mobiles, l'Institut Tropical et de Santé Publique Suisse, en partenariat avec plusieurs institutions dans la région, est actif au Sahel depuis 15 ans, aussi bien dans le domaine de la recherche, que celui des actions de développement. Basées sur une approche orientée vers les besoins des pasteurs mobiles pour leur développement, des recherches interdisciplinaires ont contribué à mieux comprendre la situation et les problèmes des éleveurs. En relation de la proximité entre l'homme et son bétail, une approche unissant la santé humaine et animale s'est avérée bonne et la valeur ajoutée d'une meilleure collaboration entre médecine humaine, animale et l'environnement a été démontrée. Ces approches utiles devraient être poursuivies et consolidées dans les recherches et le développement des actions futurs.     

Nutritional status of mauritanian children during a drought emergency

Nutritional surveys were conducted in three regions of Mauritania between September and November, 1983, to assess the impact of a severe drought and to determine priorities for relief assistance. Survey sites and children were chosen at random using established Centers for Disease Control survey methodology. A total of 1,498 children between the ages of 6 months and 5 years were weighed, measured and examined for xerophthalmia and scurvy. Information on age, sex, diarrhea, measles immunization, diet and food aid was collected for each child. Levels of acute malnutrition (< 80 % of median weight‐for‐height) ranged from 8.2 to 17.2% in the 3 regions, and both xerophthalmia and scurvy were seen. The children between 1 to 3 years of age had the highest levels of malnutrition. Food aid deliveries were irregular and inadequate in the two regions with the highest rates of malnutrition. Implications for targeting and choice of relief efforts are discussed.     

On regreening and degradation in Sahelian watersheds

Over many decades our understanding of the impacts of intermittent drought in water-limited environments like the West African Sahel has been influenced by a narrative of overgrazing and human-induced desertification. The desertification narrative has persisted in both scientific and popular conception, such that recent regional-scale recovery (“regreening”) and local success stories (community-led conservation efforts) in the Sahel, following the severe droughts of the 1970s–1980s, are sometimes ignored. Here we report a study of watershed-scale vegetation dynamics in 260 watersheds, sampled in four regions of Senegal, Mali, and Niger from 1983–2012, using satellite-derived vegetation indices as a proxy for net primary production. In response to earlier controversy, we first examine the shape of the rainfall–net primary production relationship and how it impacts conclusions regarding greening or degradation. We conclude that the choice of functional relationship has little quantitative impact on our ability to infer greening or degradation trends. We then present an approach to analyze changes in long-term (decade-scale) average rain-use efficiency (an indicator of slowly responding vegetation structural changes) relative to changes in interannual-scale rainfall sensitivity (an indicator of landscape ability to respond rapidly to rainfall variability) to infer trends in greening/degradation of the watersheds in our sample regions. The predominance of increasing rain-use efficiency in our data supports earlier reports of a “greening” trend across the Sahel. However, there are strong regional differences in the extent and direction of change, and in the apparent role of changing woody and herbaceous components in driving those temporal trends.The Sahel (Fig. S1) extends east-west across Africa between the Sahara desert to the north and the humid savanna to the south. It is one of the world’s largest water-limited environments (WLE). The region is often considered to be particularly vulnerable to climate change and human activities (1, 2). Herders and farmers in the Sahel have long recognized the importance of short-term rainfall variability on farm and livestock production, with drought being the principal cause of food insecurity (3). Rainfall largely controls net primary productivity (NPP), forage availability, and livestock carrying capacity (1), and is a primary driver of carbon cycling (4, 5). Climate variability (within and between seasons) in WLE such as the Sahel modifies the structure, composition, and diversity of vegetation via changes in NPP and recruitment-mortality dynamics of woody and herbaceous plants (6, 7).Open in a separate windowFig. S1.Averages of (A) seasonal iNDVI and (B) seasonal iR across the Sahel from July to October for the period 1983–2012. The figure also shows the location of the southwestern Niger [1], eastern Mali [2], western Mali [3], and northern Senegal [4] regions selected for further investigation.The degradation of the Sahel has been greatly debated within the scientific community. In the 1930s, after a visit to West Africa, Stebbing was one of the first to conclude that the Sahara desert was expanding south into the Sahel and that the cause of degradation was human activity (8). With above-average rainfall in the region in the 1950s and 1960s, these concerns diminished for a while. In the 1970s and 1980s, however, severe drought and famine in the Sahel, coincident with influential ideas on the potential for human mismanagement of common land (9) and the potential for amplifying feedbacks between grazing and drought (10), led to widespread acceptance in both scientific and popular imagination of Sahelian “desertification” as a pervasive and irreversible process (11, 12). In the 1990s, however, an alternative picture emerged as political ecologists and others began to question the “received wisdom” of human-induced desertification (e.g., refs. 13 and 14), perhaps motivated by recognition of the positive role of social institutions in the management of common pool resources (15) and by the recognition that degradation and recovery of Sahelian vegetation is a normal consequence of drought cycles, with or without human agency (16–19).In the last 20 y, remote-sensing studies have documented an apparent increase in vegetation productivity in the Sahel using satellite measurements of vegetation greenness (i.e., normalized difference vegetation index, NDVI) as a proxy for NPP (20–22). Independent studies have also documented farmer strategies to restore landscape-scale function, in particular through planting of trees and soil conservation actions (23, 24). Other authors, however, have used both satellite and field data to argue that the apparent “regreening” of the Sahel may still hide real degradation in the form of ecosystem ability to use available rainfall (i.e., rain-use efficiency), or in the structure and species composition of the vegetation (25–29).Meanwhile, in the popular press and often in the environmental and development literature, the reports of recovery are sometimes forgotten (30–32), to the extent that popular opinion in the West—and indeed very often in Africa—holds fast to pessimistic images of overgrazing, degradation, sand storms, and sand-dunes “marching” south from the Sahara towards the sea. The differences in perception of recent changes highlight the need to quantify the extent of recovery (or otherwise) in Sahelian systems since the droughts of the 1970s and 1980s and the extent to which vegetation changes in the Sahel respond proportionally to climate variations.Many studies have shown that the interannual variability of NPP in WLE is positively correlated with the interannual variability of rainfall (33–35). In addition, the rain-use efficiency (RUE; the slope of the relationship between NPP and rainfall) quantifies an ecosystem’s ability to use rainfall and may therefore be a useful indicator of ecosystem health or degradation. However, the use of RUE has been dominated by two contrasting schools of thought. Many authors assume that RUE will be constant with interannual variation in rainfall if ecosystem conditions are constant. In this situation, changing RUE can be used directly to diagnose changes in vegetation, reflecting long-term degradation or recovery (20, 21). Meanwhile, based on physical and physiological logic, others argue for an underlying nonlinear relationship between NPP and rainfall, with NPP initially increasing with rainfall before saturating at higher rainfall as light or nutrients become limiting (25, 27). In this situation, we no longer expect a constant RUE (calculated simply as NPP/rainfall), which compromises (or at least complicates) its utility as a degradation indicator. In all cases, however, if the functional relationship between NPP and rainfall is known, or can be derived from observations, then temporal trends in residuals from the fitted relationship can be used to infer changing ecosystem condition. This is the basis for the “residual trend” approach used by several authors to diagnose changing ecosystem health in the Sahel and other regions (36, 37).The aim of this study is to quantify the changes in vegetation condition in the Sahel based on assessments of long-term satellite-derived greenness sensitivity to rainfall. We explore changes at watershed scales in four test regions across the Sahel and examine the form (linear, nonlinear) of functional relationships between this proxy for NPP and rainfall. We then propose a new approach to the diagnosis of trends in vegetation condition that relates short-term and long-term NPP–rainfall sensitivity to changes in herbaceous and woody plants, respectively. We address the following research questions: (i) What is the shape of the rainfall–NPP relationship and its relevance to the ongoing debate of regreening of the Sahel? (ii) How has NPP varied as a function of rainfall since the 1980s drought in the Sahel? (iii) Can changes in short- and long-term NPP sensitivity to rainfall inform our understanding of changing vegetation structure in different regions of the Sahel?We based our study on a 30-y (1983–2012) African Rainfall Climatology (ARC) rainfall database (38) in combination with a merged NDVI dataset from Moderate Resolution Imaging Spectroradiometer (MODIS) (39) and Advanced Very High Resolution Radiometer (AVHRR) (40). Annual integrals of NDVI during the growing season (from June to October) are used as a proxy for NPP (20–22) over 260 watersheds located in four regions of Senegal, Mali, and Niger (Fig. S1).     

Health of mobile pastoralists in the Sahel – assessment of 15 years of research and development

In the Sahel, between Mauritania and Somalia including Northern Kenya, about 20–30 million people live as mobile pastoralists. The rhythm of their migration follows the seasons and the availability of resources such as water, pasture and salt. Despite their high exposure to zoonoses and problems caused by extreme climatic conditions, mobile pastoralists are virtually excluded from health services because the provision of social services adapted to their way of life is challenging. In cooperation with various partners in the region, the Swiss Tropical and Public Health Institute has been active in research and development in the Sahel for 15 years. Based on the perceived needs of mobile pastoralists and the necessities of development, interdisciplinary research has considerably contributed to better understanding of their situation and their problems. Close contact between humans and livestock necessitates close cooperation between human and animal health specialists. Such useful approaches should be continued and extended.     

Emergence of W135 meningococcal meningitis in Ghana

Neisseria meningitidis serogroup W135, well known for a long time as a cause of isolated cases of meningococcal meningitis, has recently increasingly been associated with disease outbreaks of considerable magnitude. Burkina Faso was hit by W135 epidemics in the dry seasons of 2002-2004, but only four W135 meningitis cases were recorded between February 2003 and March 2004 in adjoining Ghana. This reconfirms previous findings that bottlenecks exist in the spreading of new epidemic N. meningitidis clones within the meningitis belt of sub-Saharan Africa. Of the four Ghanaian W135 meningitis patients one died and three survived, of whom one had profound neurosensory hearing loss and speech impairment. All four disease isolates were sensitive to penicillin G, chloramphenicol, ciprofloxacin and cefotaxime and had the multi-locus sequence type (ST) 11, which is the major ST of the ET-37 clonal complex. Pulsed-field gel electrophoresis (PFGE) profiles of the Ghanaian disease isolates and recent epidemic isolates from Burkina Faso were largely identical. We conducted meningococcal colonization surveys in the home communities of three of the patients and in the Kassena Nankana District located at the border to Burkina Faso. W135 carriage rates ranged between 0% and 17.5%. When three consecutive surveys were conducted in the patient community with the highest carrier rate, persistence of W135 colonization over a period of 1 year was observed. Differences in PFGE profiles of carrier isolates taken at different times in the same patient community were indicative of rapid microevolution of the W135 bacteria, emphasizing the need for innovative fine typing methods to reveal the relationship between W135 isolates.     

The impact of regional climate change on malaria risk due to greenhouse forcing and land-use changes in tropical Africa

Background: Climate change will probably alter the spread and transmission intensity of malaria in Africa.Objectives: In this study, we assessed potential changes in the malaria transmission via an integrated weather–disease model.Methods: We simulated mosquito biting rates using the Liverpool Malaria Model (LMM). The input data for the LMM were bias-corrected temperature and precipitation data from the regional model (REMO) on a 0.5° latitude–longitude grid. A Plasmodium falciparum infection model expands the LMM simulations to incorporate information on the infection rate among children. Malaria projections were carried out with this integrated weather–disease model for 2001 to 2050 according to two climate scenarios that include the effect of anthropogenic land-use and land-cover changes on climate.Results: Model-based estimates for the present climate (1960 to 2000) are consistent with observed data for the spread of malaria in Africa. In the model domain, the regions where malaria is epidemic are located in the Sahel as well as in various highland territories. A decreased spread of malaria over most parts of tropical Africa is projected because of simulated increased surface temperatures and a significant reduction in annual rainfall. However, the likelihood of malaria epidemics is projected to increase in the southern part of the Sahel. In most of East Africa, the intensity of malaria transmission is expected to increase. Projections indicate that highland areas that were formerly unsuitable for malaria will become epidemic, whereas in the lower-altitude regions of the East African highlands, epidemic risk will decrease.Conclusions: We project that climate changes driven by greenhouse-gas and land-use changes will significantly affect the spread of malaria in tropical Africa well before 2050. The geographic distribution of areas where malaria is epidemic might have to be significantly altered in the coming decades.     

Diarrhoea, vomiting and the role of milk consumption: perceived and identified risk in Bamako (Mali)

OBJECTIVES: To evaluate the public health impact of milk contamination in Bamako, Mali. METHODS: A case-control study assessed the risk-factors for food-borne toxi-infections with diarrhoea and vomiting as main clinical picture. A total of 131 schoolchildren between 5 and 20 years of age were interviewed by trained interviewers in schools in Bamako. A structured questionnaire was used to record health problems, food and particularly milk consumption habits and socio-economic indicators. RESULTS: Final multivariate logistic regression analysis identified regular consumption of boiled milk [odds ratio(OR) = 4.38; 95% CI = 1.15-16.71], age between 5 and 10 years (OR vs. age group 11-15 years = 3.28; 95% CI = 1.09-9.85) and the existence of dry latrines in the household (OR = 7.65; 95% CI = 1.92-30.55) as risk factors for diarrhoea and vomiting. Other milk products and the socio-economic level of the household were not significantly associated with the outcome. Many people were unaware of the potential risks of milk consumption. CONCLUSIONS: Milk products may be a risk factor for food-borne toxi-infections. Attention has to be paid to products considered 'safe', such as boiled or pasteurized milk. The low awareness of potential risks of many people may increase the risk of milk consumption. To achieve a sustainable increase in local milk production in Africa, milk quantity and production and transformation quality should be improved simultaneously.     

Alu insertion polymorphisms in the African Sahel and the origin of Fulani pastoralists

Background: The origin of Western African pastoralism, represented today by the Fulani nomads, has been a highly debated issue for the past decades, and has not yet been conclusively resolved.

Aim: This study focused on Alu polymorphisms in sedentary and nomadic populations across the African Sahel to investigate patterns of diversity that can complement the existing results and contribute to resolving issues concerning the origin of West African pastoralism.

Subjects and methods: A new dataset of 21 Alu biallelic markers covering a substantial part of the African Sahel has been analysed jointly with several published North African populations.

Results: Interestingly, with regard to Alu variation, the relationship of Fulani pastoralists to North Africans is not as evident as was earlier revealed by studies of uniparental loci such as mtDNA and NRY. Alu insertions point rather to an affinity of Fulani pastoralists to Eastern Africans also leading a pastoral lifestyle.

Conclusions: It is suggested that contemporary Fulani pastoralists might be descendants of an ancestral Eastern African population that, while crossing the Sahara in the Holocene, admixed slightly with a population of Eurasian (as evidenced by uniparental polymorphisms) ancestry. It seems that, in the Fulani pastoralists, Alu elements reflect more ancient genetic relationships than do uniparental genetic systems.     

Microheterogeneity of serogroup A (subgroup III) neisseria meningitidis during an outbreak in northern ghana

During a meningitis outbreak in the eastern subdistrict of the Kassena-Nankana District of the Upper East Region of Ghana, we analysed cerebrospinal fluid from suspected meningitis cases for the most common causative organisms. In 50 of 92 samples analysed, serogroup A Neisseria meningitidis were detected. The ages of serogroup A N. meningitidis patients ranged from 4 months to 64 years. The case fatality ratio was 20%. Coma or stupor on presentation worsened the prognosis. All serogroup A N. meningitidis isolates recovered revealed the A: 4: P1.9, 20 phenotype characteristic for the subgroup III clonal grouping. No evidence for resistance to penicillin G, chloramphenicol, cefotaxime, ciprofloxacin, rifampicin or tetracycline was found. All strains were resistant to sulphadiazine. Restriction analysis patterns of opa, iga and ingA genes were characteristic for the majority of N. meningitidis serogroup A subgroup III bacteria isolated in Africa after the 1987 epidemic in Mecca. Differences in pulsed-field gel electrophoresis patterns of NheI and SpeI digested DNA revealed microheterogeneity among the Ghanaian isolates.