Epidemiological patterns of bacterial meningitis in Niger from 2002 to 2010

Objective: To describe the epidemiology of bacterial meningitis in Niger from January 2002 to June 2010 Methods: A retrospective study of data from the laboratory surveillance of meningitis; cerebrospinal fluid samples from suspected clinical cases were collected and tested using polymerase chain reaction and/or bacteriology for the surveillance of bacterial meningitis in Niger. Data on patients was collected using a questionnaire. Results: The number of CSF samples received was 19,273. Over 80% of the patients were under the age of 15. The overall mean age was 9 years with a range of 0 to 93 years. The mean age was lower for H. influenzae (2.4 years, SD=4.8) than for N. meningitidis (9.4 years, SD=7.9), S. pneumoniae (11.5 years, SD=13.5) and for the other bacteria (7.9 years, SD=10.1). Males were significantly more affected than females (57.4% versus 42.6%, p < 0.0001). N. meningitidis, S. pneumoniae and H. influenzae were the three main etiological agents found in 42.4% of the total tested cases. The majority of confirmed cases of the three bacteria were caused by N. meningitidis (81.6%). Serogroup A caused 75% of meningococcal meningitis cases during the study period. The highest annual incidence of N. meningitidis cases occurred in March and April and was observed in 2008-2009 (15.9 cases per 100,000 inhabitants). The annual incidence rates were most often high in the southeast, near Nigeria. S. pneumoniae and H. influenzae incidence was higher in Niamey, with 275 and 145 cases, respectively, in this town during the study period. Conclusion: This study revealed the characteristics of the bacteria involved in meningitis, and particularly the serogroups of N. meningitidis circulating in Niger, as well as the age groups and areas affected, since 2002. The implementation of the PCR technique considerably improved microbiological surveillance and made it possible to extend its use to the whole country.