[Show abstract][Hide abstract] ABSTRACT: The 2009 meningitis season in Niger was characterized by an early onset, beginning in the very first weeks of the year and peaking from the 12th to the 15th week with 5655 clinical cases over the 4 weeks. From 1 January 2009 to 28 June 2009 (week 26), a total of 13,733 clinical cases of meningitis were reported to the national epidemiological surveillance system with a case-fatality rate of 4·2%. During the season 25 of the 42 health districts reached the epidemic threshold and 11 the alert threshold. Reactive mass vaccination campaigns involving a total of 5 166,741 doses of the polysaccharide meningococcal bivalent (A+C) vaccine progressively controlled the outbreak in most parts of the country. A total of 3755 cerebrospinal fluid samples representing 28·1% of the suspected meningitis cases were analysed. Serogroup A meningococci were the causative agent in 97·5% of the meningococcal cases. Multi-locus sequence typing of 26 meningococal serogroup A strains showed 25 sequence type (ST)7 and one ST2859, both sequence types belonging to the ST5 clonal complex (CC5) of subgroup III. This is the largest epidemic observed in Niger since those of 1995-1996 (59,948 notified cases) and 2000 (14,633 notified cases).
Epidemiology and Infection 11/2011; 139(11):1656-60. DOI:10.1017/S0950268810003092 · 2.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Pastorex® (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® 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® 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® 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® 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.
PLoS ONE 10/2009; 4(10):e7326. DOI:10.1371/journal.pone.0007326 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate dipstick rapid diagnostic tests (RDTs) for meningococcal meningitis in basic health facilities.
Health facility staff received a one-day training. During the meningitis season, they performed RDTs on cerebrospinal fluid (CSF) specimens from suspected cases of meningitis. A frozen aliquot of CSF was later tested using polymerase chain reaction (PCR) to establish the reference diagnosis. RDTs used in health facilities were archived to allow checking the concordance between reported diagnosis and observed results. Reported diagnosis was also compared to PCR diagnosis. A second RDT was performed on each CSF specimen at the reference laboratory.
Using RDTs, health facilities reported 382 negative results (73.9%), 114 NmA (22.1%), 12 NmW135 (2.3%) and nine uninterpretable results (1.7%), the latter corresponding to the misuse of a reagent by three agents. The agreement between reported diagnosis and archived dipsticks was excellent (kappa = 0.98). The agreement between PCR diagnosis and reported RDTs results was strong (kappa = 0.82). In health facilities, the sensitivity of RDTs for N. meningitidis A was Se = 0.91. The kappa coefficient measuring the agreement between RDTs operated in the reference laboratory and RDTs operated in health facilities was kappa = 0.78.
We confirmed that dipstick RDTs to identify N. meningitidis serogroups A, C, W135 and Y can be reliably operated by non-specialized staff in basic health facilities. RDTs proved very useful to recommend vaccination in NmA epidemics, and also to avoid vaccination in epidemics due to serogroups not included in vaccines (NmX).
Tropical Medicine & International Health 12/2008; 14(1):111-7. DOI:10.1111/j.1365-3156.2008.02192.x · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the African meningitis belt, reported case-fatality ratio (CFR) for meningitis are usually calculated on the basis of presumed cases. We reviewed 3509 presumed cases of bacterial meningitis reported in Niger for which a cerebrospinal fluid (CSF) sample had been tested later at the reference laboratory. The main aetiologies were Neisseria meningitidis (1496 cases), Streptococcus pneumoniae (303 cases) and Haemophilus influenzae (105 cases). The CFR of meningococcal meningitis was lower for serogroup A (5.5%) than for serogroups X (12%) and W135 (12.7%). With a CFR of 49.8%, pneumococcal meningitis, albeit representing only 20.7% of confirmed cases, accounted for 50% of the deaths. The disease burden of pneumococcal meningitis must be better taken into consideration in the future. As most treatments are presumptive, there is a urgent need for an easy-to-administer, cheap first-line treatment effective on N. meningitidis as well as on S. pneumoniae and H. influenzae that would replace the single-dose oily chloramphenicol treatment which is the most frequent treatment administered today, independent of microbial aetiology and season. The development of diagnostic tools really suitable for remote health facilities also is an urgent challenge.
[Show abstract][Hide abstract] ABSTRACT: There is a great need for a rapid diagnostic test to guide vaccine choice during outbreaks of meningococcal meningitis in resource-poor countries. During a randomised clinical trial conducted during an epidemic of Neisseria meningitidis serogroup A in Niger in 2003, the sensitivity and specificity of the Pastorex latex agglutination test for this serogroup under optimal field conditions were assessed, using culture and/or PCR as the gold standard. Results from 484 samples showed a sensitivity of 88% (95% CI 85-91%) and a specificity of 93% (95% CI 90-95%). Pastorex could be a good alternative to current methods, as it can be performed in a local laboratory with rapid results and is highly specific. Sensitivity can be improved with prior microscopy where feasible. A study specifically to evaluate the Pastorex test under epidemic conditions, using laboratories with limited resources, is recommended.
Transactions of the Royal Society of Tropical Medicine and Hygiene 11/2006; 100(10):964-9. DOI:10.1016/j.trstmh.2006.03.002 · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The absence of reliable laboratories for culture of Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae, the three main causes of bacterial meningitis in Africa, hampers microbiological surveillance in these countries. To compensate for this situation in Niger, a multiplex single-tube PCR method has been implemented at a central level to test cerebrospinal fluid (CSF) samples. The overall confirmation rate for PCR (N=3791) was 40.8% compared with 16.0% for culture (N=945) (P<10(-6)). Among 850 CSF specimens tested by both methods, the overall confirmation rate was 29.4% for PCR and 16.4% for culture (P<10(-8)). PCR was also efficient for the CSF specimens stored in Trans-isolate medium. In conclusion, PCR assay is currently a key tool in Africa to improve microbiological surveillance of bacterial meningitis.
Transactions of the Royal Society of Tropical Medicine and Hygiene 08/2006; 100(7):677-80. DOI:10.1016/j.trstmh.2005.09.006 · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Microbes and Infection 07/2006; 8(8):2098-104. DOI:10.1016/j.micinf.2006.03.006 · 2.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The recent emergence of Neisseria meningitidis W135 as a cause of epidemic bacterial meningitis and the availability of a trivalent ACW135 vaccine have created a need for accurate and timely meningococcal serogroup determination for organization of epidemic vaccine response. The sensitivity and specificity of the Pastorex meningitis kit (Bio-Rad) to identify serogroups A and W135 in the African meningitis belt was assessed using PCR testing as the gold standard. The sensitivity and specificity for serogroups A and W135 were 87 and 85%, respectively, while the specificities were 93 and 97%. The positive and negative likelihood ratios for A were 12 and 0.14 and for W135 were 33 and 0.16. The positive and negative predictive values, computed to simulate an epidemic of meningococcal meningitis with an estimated 70% prevalence of N. meningitidis among suspected cases, were 97% and 75% for A and 99% and 73% for W135. In remote locations of the African meningitis belt, latex agglutination is the only currently available test that can rapidly determine meningococcal serogroup. This study showed that latex agglutination performs well and could be used during the epidemic season to determine appropriate vaccine response.
Transactions of the Royal Society of Tropical Medicine and Hygiene 07/2006; 100(6):573-8. DOI:10.1016/j.trstmh.2005.10.002 · 1.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the framework of the Human Immunodeficiency Virus (HIV) surveillance, seroprevalence and behavioural survey was conducted in 2002 in Dirkou, a place of concentration of female sex workers (FSW) in Niger The global HIV seroprevalence found was 50% (CI at 95%: 40.6-59.36%). The behavioural survey revealed that 98% of FSW had heard about HIV whereas 78.7% know at least one HIV transmission way and 76.9% know at least one HIV prevention means. Only 33.3% declared using condom, what show that sensitisation efforts are needed to induce a behaviour change in FSW and their clients.
Bulletin de la Société de pathologie exotique 04/2006; 99(1):49-51. DOI:10.3185/pathexo2830
[Show abstract][Hide abstract] ABSTRACT: Tuberculosis is hyperendemic in Niger. In Niamey between June 2002 and May 2004, 996 cerebro-spinal fluids (CSF) collected from meningitis suspected patients have been analysed by PCR for the detection of Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae: the aetiologic diagnosis was obtained for 208 cases (20.9%). The Mycobacterium tuberculosis PCR assay performed on the negative samples was positive for 4 CSF: 0.4% prevalence among suspected cases of meningitis or 1.9% among confirmed bacterial meningitis.
Bulletin de la Société de pathologie exotique 04/2006; 99(1):39-40. DOI:10.3185/pathexo2743
[Show abstract][Hide abstract] ABSTRACT: Undertaking a HIV seroepidemiological survey in Sahel is logistically problematic, since countries like Niger or Mali are very large with scattered populations and harsh climatic conditions. Therefore, the replacement of serum samples by whole blood dried on filter papers has been studied for HIV-antibody testing with commercial kits that are commonly used. In Niger, two tests ELISA (Genscreen HIV1/2 version 2, Vironostika HIV Uni-Form II Ag/Ab) and two rapid tests (Determine HIV1/2 et Immunocomb II HIV1&2 Bispot) were used to compare the dried blood spots and serum samples from 43 control individuals. Both ELISAs gave an excellent correlation (r = 0.99 et r = 0.98) between the dried blood spots and serum absorbance values. Using the rapid tests, the HIV status was found 100% concordant with dried blood spots and serum samples. An algorithm using three out of the four mentioned tests was defined then validated on the dried blood spots of 163 control individuals (100% concordant). In conclusion, dried blood spots may accurately and profitably replace serum samples for the serodiagnosis of HIV infection and for mass serosurveys in Sahel.
Bulletin de la Société de pathologie exotique 01/2006; 98(5):343-6.
[Show abstract][Hide abstract] ABSTRACT: Since the Neisseria meningitidis serogroup W135 epidemic in Burkina Faso in 2002, the neighbouring countries dread undergoing outbreaks. Niger has strongly enhanced the microbiological surveillance, especially by adding the polymerase chain reaction (PCR) assay to the national framework of the surveillance system. During the 2003 epidemic season, 8113 clinically suspected cases of meningitis were notified and nine districts of the 42 crossed the epidemic threshold, while during the 2004 season, the number of cases was 3521 and four districts notified epidemics. In 2003 and 2004, serogroup A was identified in most N. meningitidis from cerebrospinal fluid (CSF) specimens (89.7% of 759 and 87.2% of 406, respectively). Although serogroup W135 represented only 8.3% of the meningococcal meningitis in 2003 and 7.9% in 2004, and was not involved in outbreaks, it was widespread in various areas of the country. In the regions that notified epidemics, the proportion of serogroup W135 was tiny while it exceeded 40% in several non-epidemic regions. Despite the wide distribution of W135 serogroup in Niger and the fears expressed in 2001, the threat of a large epidemic caused by N. meningitidis W135 seems to have been averted in Niger so far. There is no clear indication whether this serogroup will play a lasting role in the epidemiology of meningococcal meningitis or not. As early as in the 1990s, a significant but transient increase in the incidence of N. meningitidis serogroup X was observed. Close microbiological surveillance is crucial for monitoring the threat and for identifying at the earliest the serogroups involved in epidemics.
Tropical Medicine & International Health 06/2005; 10(5):435-43. DOI:10.1111/j.1365-3156.2005.01394.x · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A national population-based survey was carried out in Niger in 2002 to assess HIV prevalence in the population aged 15-49 years. A two-stage cluster sampling was used and the blood specimens were collected on filter paper and tested according to an algorithm involving up to three diagnostic tests whenever appropriate. Testing was unlinked and anonymous. The refusal rate was 1.1% and 6056 blood samples were available for analysis. The adjusted prevalence of HIV was 0.87% (95% CI, 0.5-1.3%) and the 95% CI of the estimated number of infected individuals was 22 864-59 640. HIV-1 and HIV-2 represented, respectively, 95.6% and 2.9% of infections while dual infections represented 1.5%. HIV positivity rate was 1.0% in women and 0.7% in men. It was significantly higher among urban populations than among rural ones (respectively, 2.1% and 0.6%, P < 10(-6)). Using logistic regression, the variables significantly related to the risk of being tested positive for HIV were urban housing, increasing age and being either widowed or divorced. The estimate from the national survey was lower than the prevalence assessed from antenatal clinic data (2.8% in 2001). In the future, the representativeness of sentinel sites should be improved by increasing the representation of rural areas accounting for more than 80% of the population. Compared with other sub-Saharan countries, the HIV prevalence in Niger is still moderate. This situation represents a strong argument for enhancing prevention programmes and makes realistic the projects promoting an access to potent antiretroviral therapies for the majority.
Tropical Medicine & International Health 11/2004; 9(11):1161-6. DOI:10.1111/j.1365-3156.2004.01324.x · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To compensate for the lack of laboratories in remote areas, the national reference laboratory for meningitis in Niger used polymerase chain reaction (PCR) to enhance the surveillance of meningitis caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. PCR effectively documented the wide geographic spread of N. meningitidis serogroup W135.