Changing Pattern of Childhood Epidemic Cerebrospinal Meningitis in North-Western Nigeria

INTRODUCTION

Nigeria lies within the meningitis belt which extends from the Gambia, Senegal through Nigeria to Eritrea; however, outbreaks have been shown to extend further south involving countries such as Angola and Namibia.[12] Epidemic outbreaks are often recorded every 8–12 years averaging in a 10 yearly circle;[3] however, endemic cases still occurs.[456] Neisseria meningitidis is the commonest organism implicated in epidemic meningitis, and 9 serotypes have been identified; these are, namely, A, B, C, D, X, Y, Z, W-135, and 29 E; however, group A and occasionally group C are implicated in most epidemics in sub-Saharan Africa;[7] in an earlier report by Mado et al.[8] 77 cases of cerebrospinal meningitis (CSM) were documented over a 12-month period (2009) in their tertiary institution; however, their result showed that N. meningitidis serogroup A was positive in all of the 77 cerebrospinal fluid (CSF) sampled through latex particle agglutination test (LPA); however, only five positive CSF cultures for N. meningitidis were obtained and an additional five patients had nonmeningococcal meningitis during the epidemics (three pneumococcus and two Haemophilus influenzae). The serotype A had been documented as the predominant strain in most reports of outbreaks in northern Nigeria and Niger Republic.[9] However, this differed from that of Osuorah et al.[10] who reported more of W135 in an outbreak in the Gambia in 2012. However, in 2010, large pool of samples was received from several health facilities in Zamfara state and beyond with diagnosis of meningitis; this study, therefore, seeks to determine the organisms implicated, the serotypes involved and if there was any change in the serotype from those reported in the previous year. Identifying the responsible serotype has important disease preventive role in implementing effective surveillance and vaccination programs.

MATERIALS AND METHODS

The study was retrospective; all results of CSF samples of children with meningitis collected from January 2010 to December 2010 were collected from the register of the microbiology laboratory of General Hospital Gusau. The relevant information such as their age, sex, CSF macroscopy/microscopy reports, LPA test report, and CSF culture report were retrieved and entered into a pro forma. Approval for this study was obtained from the State Ethical Committee on clinical research. The Farida General Hospital Gusau laboratory was the reference center for CSF analysis for the state and its being supported by Federal Ministry of Health, State Ministry of Health and World Health Organization (WHO), so all samples are sent from all health facility and standard WHO protocol for case definition and laboratory procedures are highly maintained.

RESULTS

There were 89 (73%) males and 33 (27%) females with male to female ratio of 2.7:1. The age range of the individuals was from 2 months to 14 years; the mean age was 6.27 ± 4.00 years.

Samples for cases of meningitis were mostly recorded from January to April and the highest record was March (89; 73%) while April (1; 0.8%) had the least; February and January had 28 (23%) and 4 (3.3%), respectively [Figure 1].

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Figure 1

Monthly distribution of cases of meningitis

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Majority of the samples were received from subjects who were within their childhood (36.1%) while infants were the least (13.1%). Most of the samples were from participants within the 1–5 years of age group (41.8%) while those <1 year were the least (6.6%) [Table 1].

Table 1 Demographic characteristics of the study group

Most of the samples were turbid at submission (74; 60.7%) while 48 (39.3%) were clear. The mean cell count was 0.8 × 10⁹/L ± 1.9 × 10⁹/L; absent cell (81.1%) in the CSF was the most common observation, while only 9 (7.4%) samples had more than 5 cells in the CSF [Table 2].

Table 2 Cell count and serotypes of the obtained cerebrospinal fluid

N. meningitidis serotype W135 was the most common serotype identified, while 44.3% of them were nonreactive, serotype A was the least recorded.

Majority of the samples (54) which were nonreactive for any of the tested antigen had a clear CSF (36), while among those that were reactive; the W135 group had high proportion of cases that had turbid CSF (44); this observation was noted to be statistically significant (‡Fisher's exact test = 30.650, P = 0.000).

Higher proportion (62) of the samples with absent cells appeared turbid at submission, however, all the samples with the highest cell counts were turbid at presentation, this observation was not statistically significant (†Fisher's exact test = 6.006, P = 0.091) [Table 3].

Table 3 Comparing the serotypes and cell count with the cerebrospinal fluid turbidity

Majority of the samples (99) had no cell count (0) although those of the W135 group had higher cell counts followed by those in the nonreactive group, however it was not statistically significant (Fisher's exact test = 11.226, P = 0.181) [Table 4].

Table 4 Comparing the serotypes with the cell counts

DISCUSSION

Meningococcal disease outbreaks occur in the semi-arid region of sub-Saharan Africa which has been described by the WHO as the meningitis belt; northern Nigeria lies within this description, therefore, reports of epidemics are not uncommon; however, infection caused by other strains of bacteria and nonbacterial organisms are also observed in the region. Outbreaks of CSM often occur during the hot season between December to June.[11]

This study showed that more males were affected than females, this observation was similar to that reported by Tavasoli et al.[12] and Heydarian et al.[13] both in Iran; similarly, Lagunju et al.[14] in Ibadan and Frank-Briggs and Alikor[15] in Port-Harcourt reported the same pattern of male predominance; why this is so is not clearly understood, however, the role of sex variation in the development of the immune system and susceptibility to various bacterial infection as was reported by Green[16] is plausible.

Samples were mostly received from January to April and March had the highest; this observation was slightly different from the previous reports;[1718] Mado et al.[8] in the 2009 CSM outbreak, cases were recorded up to May; and April recorded the highest cases followed by March.

The W135 serotype was the predominant strain in this study; this was a great departure from previous reports[89] which showed A serotype as the most common cause of outbreak; however, our result was similar to that of Osuorah et al.[10] in their report from the Gambia. The world is a global village; with the ease of travel introduction of alien serotypes is not an uncommon phenomenon.

The age distribution in this study was similar to the previous reports of Odedina and Emumwen,[19] Mado et al.;[8] (those <1 year constituting 6.6%) and Emele and Anyiwo[20] but contrasted with that of Mohammed et al.[21] and Bwala et al.[22] who reported high incidence in infancy. They attributed their experience to the impact of virulence of the subgroups involved in their outbreak.

Seventy-four (60.7%) of the sample were reported turbid; this was higher than the 2% reported by Odedina and Emumwen;[19] the reason for the difference was not clear, however, turbidity is subjective, therefore milder grades of severity are often prone to either been under or overestimated. However, the culture yield was low in this study when compared to 6.5% by Mado et al.[8] and 14% by Odedina and Emumwen;[19] no positive culture was obtained in this study.

Ninety-nine (81.1%) of the samples had absent neutrophil in the CSF; absent CSF neutrophilic pleocytosis has been associated with meningococcal meningitis,[23] especially following early lumbar puncture sampling; therefore, repeat sampling is advised in such settings. Furthermore, our laboratory received samples from distant health facilities; therefore, the possibility of degradation was also entertained.

CONCLUSION

This study showed that epidemic meningitis was highest between January and April, and the predominant serotype (W135) was a great departure from the usual; therefore, this highlights the significant of continuous surveillance, which facilitates efficient vaccination program.