Field Evaluation of the Performance of Two Rapid Diagnostic Tests for Meningitis in Niger and Burkina Faso.

New lateral flow tests for the diagnosis of Neisseria meningitidis (Nm) (serogroups A, C, W, X, and Y), MeningoSpeed, and Streptococcus pneumoniae (Sp), PneumoSpeed, developed to support rapid outbreak detection in Africa, have shown good performance under laboratory conditions. We conducted an independent evaluation of both tests under field conditions in Burkina Faso and Niger, in 2018-2019. The tests were performed in the cerebrospinal fluid of suspected meningitis cases from health centers in alert districts and compared to reverse transcription polymerase chain reaction tests performed at national reference laboratories (NRLs). Health staff were interviewed about feasibility. A total of 327 cases were tested at the NRLs, with 26% confirmed Nm (NmC 63% and NmX 37%) and 8% Sp. Sensitivity and specificity were, respectively, 95% (95% CI: 89-99) and 90% (95% CI: 86-94) for Nm and 92% (95% CI: 75-99) and 99% (95% CI: 97-100) for Sp. Positive and negative predictive values were, respectively, 77% (95% CI: 68-85) and 98% (95% CI: 95-100) for Nm and 86% (95% CI: 67-96) and 99% (95% CI: 98-100) for Sp. Concordance showed 82% agreement for Nm and 97% for Sp. Interviewed staff evaluated the tests as easy to use and to interpret and were confident in their readings. Results suggest overall good performance of both tests and potential usefulness in meningitis outbreak detection.

Vulnerability of African Rosewood (Pterocarpus erinaceus, Fabaceae) natural stands to climate change and implications for silviculture in West Africa.

Pterocarpus erinaceus is a native tree species of the Guineo-Sudanian and Sudano-Sahelian zones where natural stands are under constant pressure and heavily exploited for timber, animal feeding and others uses. A part from the overexploitation, climate change could also become a serious threat to the species natural distribution. For that purposes, this study aims to assess the vulnerability of P. erinaceus potential niche to climate change within its natural distribution area in West Africa. Niche predictions are based on 6,981 natural occurrence of the species and 19 global bioclimatic variables available through WorldClim. The future niche of the species is predicted according to three concentration pathways (RCPs 2.6, 4.5 and 8.5) of BC model for 2050 and 2070, thanks to Maxent software. P. erinaceus is currently reported from Senegal to Cameroon. Its potential niche covers the Sudano-Sahelian zone and the Dahomey gap on approximately 17.42% of the total area of these countries. In general, the niche of the species is not sensitive to climate change, regardless of the climate scenario and the year. Compared to its initial niche, the niche of the species will increase from 22.33% to 43.61% in 2050 and from 27.12% to 53.61% in 2070. However, this ecological expansion observed mainly in the Gulf of Guinea, will be associated with a considerable decrease in the Sahel and central Nigeria. This study shows the importance of promoting the development of innovative silvicultural strategies for the extension and restoration of natural stands of P. erinaceus in order to meet sustainably the timber needs of the West African region. It helps also to strengthening the roles of natural forests in providing ecosystem services and mitigating climate change effects.

Using agricultural residues for sustainable transportation biofuels in 2050: Case of West Africa.

This article focuses on the use of biomass to produce transportation fuels such as synthetic natural gas, bioethanol and electricity under a sustainable scenario in West Africa in 2050. The aim of this work was to evaluate the feasibility of producing such biofuels using agricultural residues as feedstock in the studied area. The potential of biomass from ten agricultural residues was estimated in R environment using FAO data. Options were analyzed in order to generate portfolios of transportation fuels based on energy indicators, biomass availability and scenarios of technological progress. The optimal allocation varied from one country to the other, showing a fair tradeoff between the objective functions.

Dynamic relationship of traditional soil restoration practices and climate change adaptation in semi-arid Niger.

Climate change increases the vulnerability of agrosystems to soil degradation and reduces the effectiveness of traditional soil restoration options. The implementation of some practices need to be readjusted due to steadily increasing temperature and lowering precipitation. For farmers, the best practice found, should have the potential to achieve maximum sustainable levels of soil productivity in the context of climate change. A study was conducted in South-West Niger to investigate the use of the suitable practice, through (i) a meta-analysis of case studies, (ii) using field survey and (iii) by using AquaCrop model. Results showed that the effects of the association zaï + mulch on crop yield was up to 2 times higher than control plots depending on climate projections scenario RCP 8.5 under which carbon dioxide (CO2) concentrations are projected to reach 936 ppm by 2100. The practice appeared to be an interesting option for enhancing crop productivity in a context of climate change. Concerning its ability, it offers the best prospects to reverse soil degradation in the study area. In addition, the simulation showed that this strategy was suitable for timely sowing and therefore confirmed scholars and farmers views. Furthermore, this practice is relatively more effective compared to the others practices. These results show that association zaï + mulch could be considered as the best practice that can participate to a successful adaptation to reduce risk from climate change at the same time by reducing the vulnerability of farmers in Southwest of Niger for now and even for the future.

Validation of a New Rapid Detection Test for Detection of Neisseria meningitidis A/C/W/X/Y Antigens in Cerebrospinal Fluid.

Meningococcal meningitis remains a life-threatening disease worldwide, with high prevalence in the sub-Saharan meningitis belt. A rapid diagnosis is crucial for implementing adapted antimicrobial treatment. We describe the performances of a new immunochromatographic test (MeningoSpeed, BioSpeedia, France) for detecting and grouping Neisseria meningitidis Cerebrospinal fluids (CSFs) were collected from 5 African countries and France. For the rapid diagnostic test (RDT), the CSF sample was deposited on each of the 3 cassettes for a total volume of 90 µl. The results of the RDT were compared to those of a reference multiplex PCR assay detecting the major serogroups of N. meningitidis on 560 CSF specimens. Five specimens were found uninterpretable by RDT (0.9%). The results of interpretable specimens were as follows: 305 positive and 212 negative samples by both techniques, 14 positive by PCR only, and 24 positive by RDT only (sensitivity, specificity, and positive and negative predictive values of 92.7%, 93.8%, 95.6%, and 89.8%, respectively, with an accuracy of 93.2% and a kappa test of 0.89; P < 0.05). From 319 samples positive by PCR for serogroups A, C, W, X, or Y, the grouping results were concordant for 299 specimens (sensitivity of 93.0%, 74.4%, 98.1%, 100%, and 83.3% for serogroups A, C, W, X, and Y, respectively). The MeningoSpeed RDT exhibited excellent performances for the rapid detection of N. meningitidis antigens. It can be stored at room temperature, requires a minimal amount of CSF, is performed in 15 minutes or less, and is easy to use at bedside.

Epidemiology of Bacterial Meningitis in the Nine Years Since Meningococcal Serogroup A Conjugate Vaccine Introduction, Niger, 2010-2018.

BACKGROUND: In 2010, Niger and other meningitis belt countries introduced a meningococcal serogroup A conjugate vaccine (MACV). We describe the epidemiology of bacterial meningitis in Niger from 2010 to 2018. METHODS: Suspected and confirmed meningitis cases from January 1, 2010 to July 15, 2018 were obtained from national aggregate and laboratory surveillance. Cerebrospinal fluid specimens were analyzed by culture and/or polymerase chain reaction. Annual incidence was calculated as cases per 100 000 population. Selected isolates obtained during 2016-2017 were characterized by whole-genome sequencing. RESULTS: Of the 21 142 suspected cases of meningitis, 5590 were confirmed: Neisseria meningitidis ([Nm] 85%), Streptococcus pneumoniae ([Sp] 13%), and Haemophilus influenzae ([Hi] 2%). No NmA cases occurred after 2011. Annual incidence per 100 000 population was more dynamic for Nm (0.06-7.71) than for Sp (0.18-0.70) and Hi (0.01-0.23). The predominant Nm serogroups varied over time (NmW in 2010-2011, NmC in 2015-2018, and both NmC and NmX in 2017-2018). Meningococcal meningitis incidence was highest in the regions of Niamey, Tillabery, Dosso, Tahoua, and Maradi. The NmW isolates were clonal complex (CC)11, NmX were CC181, and NmC were CC10217. CONCLUSIONS: After MACV introduction, we observed an absence of NmA, the emergence and continuing burden of NmC, and an increase in NmX. Niger's dynamic Nm serogroup distribution highlights the need for strong surveillance programs to inform vaccine policy.

Measurement of pneumococcal IgG antibody, carriage and infection with Streptococcus pneumoniae in children under five years of age with acute respiratory infection in Niger.

Pneumonia is the major cause of mortality in children under five years. A total of 751 children aged 1-59 months admitted for acute respiratory infection were included in this study. Pneumococcal serum IgG antibody was determined by ELISA. Carriage of Streptococcus pneumoniae was determined by molecular analyses of nasopharyngeal swabbings, and the rapid urinary diagnostic test Binax NOW®Sp was used for detection of pneumococcal antigen in urine. A total of 224 (29.8%) children had vaccination record books, and among them, 186 (83%) were vaccinated with the 23-Valent Pneumococcal Polysaccharide Vaccine (PPSV-23), 7 (3%) were vaccinated with the 13-Valent Pneumococcal Conjugate Vaccine (PCV-13), and 31 (14%) had not been vaccinated. IgG levels against pneumococcal polysaccharide were ≥1.3µg/mL in most of the children (99.4%). The carriage rate of S. pneumoniae was 39%, and the Binax NOW®Sp test was positive in 26% of children. There was no significant variation between the means of IgG concentrations against pneumococcal polysaccharides as related to vaccination status, age and nasopharyngeal carriage of S. pneumoniae. However, there was a weak positive correlation between age and level of IgG (r=0.08; p=0.021), and there was a significant variation (p=0.038) of the IgG level according to presence of S. pneumoniae antigen in urine. The presence of S. pneumoniae antigen in urine is significantly (p≤0.01) higher in children with nasopharyngeal carriage of S. pneumoniae (40%) than non-carriers (20%). This study shows that S. pneumoniae has high circulation in children under the age of five years either through infection or carriage.

Correction: A Seroepidemiological Study of Serogroup A Meningococcal Infection in the African Meningitis Belt.

[This corrects the article DOI: 10.1371/journal.pone.0147928.].

A Seroepidemiological Study of Serogroup A Meningococcal Infection in the African Meningitis Belt.

The pattern of epidemic meningococcal disease in the African meningitis belt may be influenced by the background level of population immunity but this has been measured infrequently. A standardised enzyme-linked immunosorbent assay (ELISA) for measuring meningococcal serogroup A IgG antibodies was established at five centres within the meningitis belt. Antibody concentrations were then measured in 3930 individuals stratified by age and residence from six countries. Seroprevalence by age was used in a catalytic model to determine the force of infection. Meningococcal serogroup A IgG antibody concentrations were high in each country but showed heterogeneity across the meningitis belt. The geometric mean concentration (GMC) was highest in Ghana (9.09 µg/mL [95% CI 8.29, 9.97]) and lowest in Ethiopia (1.43 µg/mL [95% CI 1.31, 1.57]) on the margins of the belt. The force of infection was lowest in Ethiopia (λ = 0.028). Variables associated with a concentration above the putative protective level of 2 µg/mL were age, urban residence and a history of recent vaccination with a meningococcal vaccine. Prior to vaccination with the serogroup A meningococcal conjugate vaccine, meningococcal serogroup A IgG antibody concentrations were high across the African meningitis belt and yet the region remained susceptible to epidemics.

Development and evaluation of a dipstick diagnostic test for Neisseria meningitidis serogroup X.

The emergence of Neisseria meningitidis serogroup X (NmX) in the African meningitis belt has urged the development of diagnostic tools and vaccines for this serogroup, especially following the introduction of a conjugate vaccine against N. meningitidis serogroup A (NmA). We have developed and evaluated a new rapid diagnostic test (RDT) for detecting the capsular polysaccharide (cps) antigen of this emerging serogroup. Whole inactivated NmX bacteria were used to immunize rabbits. Following purification by affinity chromatography, the cpsX-specific IgG antibodies were utilized to develop an NmX-specific immunochromatography dipstick RDT. The test was validated against purified cpsX and meningococcal strains of different serogroups. Its performance was evaluated against that of PCR on a collection of 369 cerebrospinal fluid (CSF) samples obtained from patients living in countries within the meningitis belt (Cameroon, Côte d'Ivoire, and Niger) or in France. The RDT was highly specific for NmX strains. Cutoffs of 10(5) CFU/ml and 1 ng/ml were observed for the reference NmX strain and purified cpsX, respectively. Sensitivity and specificity were 100% and 94%, respectively. A high agreement between PCR and RDT (Kappa coefficient, 0.98) was observed. The RDT gave a high positive likelihood ratio and a low negative likelihood (0.07), indicating almost 100% probability of declaring disease or not when the test is positive or negative, respectively. This unique NmX-specific test could be added to the available set of RDT for the detection of meningococcal meningitis in Africa as a major tool to reinforce epidemiological surveillance after the introduction of the NmA conjugate vaccine.

A five-year field assessment of rapid diagnostic tests for meningococcal meningitis in Niger by using the combination of conventional and real-time PCR assays as a gold standard.

BACKGROUND: Meningococcocal meningitis represents an important cause of mortality and morbidity in sub-Saharan countries. Confirmatory bacteriological or molecular diagnosis is essential for patient management/treatment and meningitis surveillance, but many laboratory tests are expensive and rarely available for low-income countries. A rapid diagnostic test (RDT) represents a valuable alternative to improve case management and surveillance. METHODS: A dipstick RDT developed in early 2000s that detects Neisseria meningitidis serogroups A, C, W and Y but for which a new conjugated antibody (L4-8) for the detection of serogroup A replaced the original K15-2 was assessed in the field by trained staff from health centres and district hospitals in Niger. The results were compared to those obtained in the reference laboratory and the sensitivity and specificity of RDTs were determined using conventional and real-time PCR assays as a gold standard. RESULTS: RDT results from field staff and the reference laboratory obtained for 2095 cerebrospinal fluid (CSF) specimens presented a strong concordance of 94% with Cohen's κ coefficient of 0.88. The observed concordance between RDTs operated by staff from the reference laboratory vs combination of conventional and real-time PCR assays was 89% with Cohen's κ coefficient of 0.76 indicating very good agreement. The theoretical overall sensitivity for RDT was 91.5% and the specificity 84.6%. CONCLUSIONS: RDT has proven to be relatively sensitive and specific for the detection of meningococcal serogroups A/C/Y/W. We confirmed that these RDTs can be reliably operated by trained but non-specialised staff in basic health facilities.

Field evaluation of two rapid diagnostic tests for Neisseria meningitidis serogroup A during the 2006 outbreak in Niger.

The Pastorex((R)) (BioRad) rapid agglutination test is one of the main rapid diagnostic tests (RDTs) for meningococcal disease currently in use in the "meningitis belt". Earlier evaluations, performed after heating and centrifugation of cerebrospinal fluid (CSF) samples, under good laboratory conditions, showed high sensitivity and specificity. However, during an epidemic, the test may be used without prior sample preparation. Recently a new, easy-to-use dipstick RDT for meningococcal disease detection on CSF was developed by the Centre de Recherche Médicale et Sanitaire in Niger and the Pasteur Institute in France. We estimate diagnostic accuracy in the field during the 2006 outbreak of Neisseria meningitidis serogroup A in Maradi, Niger, for the dipstick RDT and Pastorex((R)) on unprepared CSF, (a) by comparing each test's sensitivity and specificity with previously reported values; and (b) by comparing results for each test on paired samples, using McNemar's test. We also (c) estimate diagnostic accuracy of the dipstick RDT on diluted whole blood. We tested unprepared CSF and diluted whole blood from 126 patients with suspected meningococcal disease presenting at four health posts. (a) Pastorex((R)) sensitivity (69%; 95%CI 57-79) was significantly lower than found previously for prepared CSF samples [87% (81-91); or 88% (85-91)], as was specificity [81% (95%CI 68-91) vs 93% (90-95); or 93% (87-96)]. Sensitivity of the dipstick RDT [89% (95%CI 80-95)] was similar to previously reported values for ideal laboratory conditions [89% (84-93) and 94% (90-96)]. Specificity, at 62% (95%CI 48-75), was significantly lower than found previously [94% (92-96) and 97% (94-99)]. (b) McNemar's test for the dipstick RDT vs Pastorex((R)) was statistically significant (p<0.001). (c) The dipstick RDT did not perform satisfactorily on diluted whole blood (sensitivity 73%; specificity 57%).Sensitivity and specificity of Pastorex((R)) without prior CSF preparation were poorer than previously reported results from prepared samples; therefore we caution against using this test during an epidemic if sample preparation is not possible. For the dipstick RDT, sensitivity was similar to, while specificity was not as high as previously reported during a more stable context. Further studies are needed to evaluate its field performance, especially for different populations and other serogroups.

Controlling schistosomiasis: significant decrease of anaemia prevalence one year after a single dose of praziquantel in Nigerian schoolchildren.

BACKGROUND: In the framework of the monitoring and evaluation of the Nigerian schistosomiasis and soil-transmitted helminth control programme, a follow-up of children took place in eight sentinel sites. The objective of the study was to assess the evolution of Schistosoma haematobium infection and anaemia in schoolchildren after a single administration of praziquantel (PZQ) and albendazole. METHODS/PRINCIPAL FINDINGS: Pre-treatment examination and follow-up at one year post-treatment of schoolchildren aged 7, 8, and 11 years, including interview, urine examination, ultrasound examination of the urinary tract, and measurement of haemoglobin. Before treatment, the overall prevalence of S. heamatobium infection was 75.4% of the 1,642 enrolled children, and 21.8% of children excreted more than 50 eggs/10 ml urine. Prevalence increased with age. The overall prevalence of anaemia (haemoglobin <11.5 g/dl) was 61.6%, decreasing significantly with increasing age. The mean haemoglobinemia was 11 g/dl. In bivariate analysis, anaemia was significantly more frequent in children infected with S. haematobium, although it was not correlated to the intensity of infection. Anaemia was also associated with micro-haematuria and to kidney distensions. In a sub-sample of 636 children tested for P. falciparum infection, anaemia was significantly more frequent in malaria-infected children. In multivariate analysis, significant predictors of anaemia were P. falciparum infection, kidney distension, and the village. One year after a single-dose praziquantel treatment (administered using the WHO PZQ dose pole) co-administered with albendazole (400 mg single dose) for de-worming, the prevalence of S. haematobium infection was 38%, while the prevalence of anaemia fell to 50.4%. The mean haemoglobinemia showed a statistically significant increase of 0.39 g/dl to reach 11.4 g/dl. Anaemia was no longer associated with S. haematobium or to P. falciparum infections, or to haematuria or ultrasound abnormalities of the urinary tract. CONCLUSIONS: The high prevalence of anaemia in Nigerian children is clearly a result of many factors and not of schistosomiasis alone. Nevertheless, treatment of schistosomiasis and de-worming were followed by a partial, but significant, reduction of anaemia in schoolchildren, not explainable by any other obvious intervention.

New rapid diagnostic tests for Neisseria meningitidis serogroups A, W135, C, and Y.

BACKGROUND: Outbreaks of meningococcal meningitis (meningitis caused by Neisseria meningitidis) are a major public health concern in the African "meningitis belt," which includes 21 countries from Senegal to Ethiopia. Of the several species that can cause meningitis, N. meningitidis is the most important cause of epidemics in this region. In choosing the appropriate vaccine, accurate N. meningitidis serogroup determination is key. To this end, we developed and evaluated two duplex rapid diagnostic tests (RDTs) for detecting N. meningitidis polysaccharide (PS) antigens of several important serogroups. METHODS AND FINDINGS: Mouse monoclonal IgG antibodies against N. meningitidis PS A, W135/Y, Y, and C were used to develop two immunochromatography duplex RDTs, RDT1 (to detect serogroups A and W135/Y) and RDT2 (to detect serogroups C and Y). Standards for Reporting of Diagnostic Accuracy criteria were used to determine diagnostic accuracy of RDTs on reference strains and cerebrospinal fluid (CSF) samples using culture and PCR, respectively, as reference tests. The cutoffs were 10(5) cfu/ml for reference strains and 1 ng/ml for PS. Sensitivities and specificities were 100% for reference strains, and 93.8%-100% for CSF serogroups A, W135, and Y in CSF. For CSF serogroup A, the positive and negative likelihood ratios (+/- 95% confidence intervals [CIs]) were 31.867 (16.1-63.1) and 0.065 (0.04-0.104), respectively, and the diagnostic odds ratio (+/- 95% CI) was 492.9 (207.2-1,172.5). For CSF serogroups W135 and Y, the positive likelihood ratio was 159.6 (51.7-493.3) Both RDTs were equally reliable at 25 degrees C and 45 degrees C. CONCLUSIONS: These RDTs are important new bedside diagnostic tools for surveillance of meningococcus serogroups A and W135, the two serogroups that are responsible for major epidemics in Africa.

Prospective survey on carriage of Neisseria meningitidis and protective immunity to meningococci in schoolchildren in Niamey (Niger): focus on serogroup W135.

We investigated the carriage of serogroup W135 meningococci and its relationship with protective immunity in Niamey. Between February and May 2003, three oropharyngeal swabs and two serum samples were each taken from 287 school children. Serogroup W135 isolates were obtained from 8.9% of children. Specific IgG > or = 2 microg/ml using ELISA or serum bactericidal assay (SBA) titre > or = 8 were supposed to represent the protective immunity to a serogroup. The proportion of children with serogroup W135-specific IgG > or = 2 microg/ml increased significantly during follow-up (13.9% to 19.1%), but not the proportion of those with SBA titre > or = 8 (10.1% to 11.6%). At the end of the follow-up, we observed a significant association between carriage of serogroup W135 strains and presumed protective immunity to this serogroup, using either ELISA or SBA. Among 240 children having an initial SBA titre < 8, 20 carried serogroup W135 strains at least once. In May, 25% of carriers had an SBA titre > or = 8, vs. 2.3% of non-carriers. For ELISA, 230 children had specific IgG < 2 microg/ml in February, with 22 having at least one swab positive for serogroup W135 meningococci later. In May, 45.5% of them had specific IgG > or = 2 microg/ml vs. 5.3% among non-carriers.

Fuelwood harvesting in Niger and a generalization of Faustmann's formula.

In some forests of Niger where 'controlled rural markets' have been organized, fuelwood is harvested following a policy of the form: every T year, cut the dead trees and those live trees which have a diameter greater than D. Dead trees generally form the main part of the harvest. In this paper, we present a simple continuous time model for the management of these uneven-aged stands subject to a high natural death rate alpha, and we derive a formula for the cycle length and the diameter optimizing the discounted income over an infinite horizon. Faustmann's classical formula for even-aged stands corresponds to the limit alpha --> 0 and D = 0 (clear-cut).