Academic journal article Bulletin of the World Health Organization

Epidemiology of Bacterial Meningitis in Niamey, Niger, 1981-96

Academic journal article Bulletin of the World Health Organization

Epidemiology of Bacterial Meningitis in Niamey, Niger, 1981-96

Article excerpt

Voir page 506 le resume en francais. En la pagina 507 figura un resumen en espanol.


Niamey, the capital of Niger, lies in the centre of the African meningitis belt (1), an area which experiences repeated epidemics of meningococcal meningitis in addition to a substantial number of cases of endemic meningitis. This situation poses a serious public health threat to the region, compared with other parts of the world. The last wave of epidemic meningococcal meningitis in Niger, which began in 1995, affected several countries during the following two years (2, 3). A total of 41 930 meningitis cases and 3639 deaths were reported in Niger in 1995 (4).

Epidemics of meningococcal meningitis in the meningitis belt are relatively well documented, as a result of investigations carried out during control efforts (5-10). In contrast, only a few studies in sub-Saharan Africa have reported the rates of bacterial meningitis during non-epidemic periods, and characterized the specific agents causing endemic meningitis (11-13). Cerebrospinal fluid (CSF) analyses have been carried out in the Centre de Recherche sur les Meningites et les Schistosomiases (CERMES) since 1981, and provide retrospective data on the epidemiology of both endemic and epidemic bacterial meningitis in Niamey over a 15-year period. These estimates of the burden of illness and deaths due to bacterial meningitis might suggest priorities in the use of currently available vaccines and help in the evaluation of new vaccines against the three principal etiological agents -- Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae b (Hib).

Materials and methods

Study population and geographical setting

Most of the 9-million population of Niger, one of the world's poorest countries, live in the southern, agricultural region. The climate is typical of that in the meningitis belt, with a distinct dry season (November to April) during which the Harmattan dust and sand storms occur. The rainy season begins in May or June and lasts until October. Niamey is densely populated (total: 547 743 in 1995), especially during the dry season when people migrate from the rural areas and return to their villages when the rains begin. Resources for health care are limited.

Data collection

The bacteriology laboratory of CERMES processes all CSF specimens submitted by the infectious disease service of the National Hospital of Niamey, where all cases of suspected meningitis in Niamey are treated. CSF specimens are obtained only rarely in the other wards of the hospital or at other health centres in Niamey.

Laboratory registers containing the results of CSF analysis served as the initial source of data for this study, which covered all specimens collected from 1 September 1981 to 30 June 1996. For each case, we recorded information on demographic characteristics and CSF analysis (cell count, Gram stain, culture and serology); excluded were CSF specimens that were collected to monitor a patient's response to antibiotic therapy. We also reviewed hospital registers to determine the outcome of the infection and any missing demographic data. Hospital records were available only for the period 1989-96.

Laboratory methods

Standard methods were used for the analysis of CSF specimens and serogrouping of meningococci (14). Until 1994, latex agglutination testing was routinely conducted on specimens using the Slidex Meningitis Kit-5 (BioMerieux, Marcy-Etoile, France, reference No. 58803), which identifies H.. influenzae type b, N. meningitidis A, B, or C; or S. pneumoniae. Counter-immunoelectrophoresis was used rarely. Additional serogrouping of selected isolates of N. meningitidis was carried out at the French Army's Pharo Laboratory in Marseilles or the Institut Pasteur in Paris.

Antimicrobial susceptibility was tested at CERMES for some specimens collected between 1985 and 1996 by the disk method using Bio-discs (BioMerieux, reference No. …

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