Antipneumococcal seroprevalence and pneumococcal carriage during a meningococcal epidemic in Burkina Faso, 2006.

BACKGROUND: To better understand the high incidence of pneumococcal meningitis in the African meningitis belt, we conducted a pneumococcal seroprevalence study during a meningococcal meningitis epidemic in Western Burkina Faso, March 2006. METHODS: In 3 villages experiencing epidemics, we included 624 healthy persons (1-39 years) by cluster sampling. We determined pneumococcal serum immunoglobulin G (IgG) antibody concentrations against 12 serotypes contained in 13-valent pneumococcal conjugate vaccine, and evaluated determinants for IgG ≥ 0.35 µg/mL by multivariate logistic regression. RESULTS: The percentage of subjects with serotype-specific IgG concentrations ≥0.35 µg/mL increased with age and was similar for the different serotypes: it was 20%-43% among 1-4-year-olds and 56%-90% among 20-39-year-olds. Prevalence of IgG ≥ 0.35 µg/mL against serotype 1 was up to 71% after age 10 years. During multivariate analyses, determinants of IgG concentrations ≥0.35 µg/mL varied by serotype; for 5 and 6 serotypes, respectively, female sex (around 2-fold increased odds) and cigarette smoking (about 5-fold reduced odds) predicted elevated titers. CONCLUSIONS: Despite a substantially higher historical pneumococcal meningitis incidence in Burkina Faso, the general population has an antibody seroprevalence against 12 pneumococcal serotypes similar to that reported from the United Kingdom. The role of putatively protective antibody seroprevalence in preventing pneumococcal meningitis in the meningitis belt requires more thorough evaluation.

Seroprevalence of bactericidal, specific IgG antibodies and incidence of meningitis due to group A Neisseria meningitidis by age in Burkina Faso 2008.

BACKGROUND: We investigated serological correlates of protection against Neisseria meningitidis serogroup A (NmA) in Burkina Faso before the introduction of NmA conjugate vaccine. METHODOLOGY/PRINCIPAL FINDINGS: We collected blood from a representative sample (N = 1022) of Bobo-Dioulasso residents. Sera were evaluated for serum bactericidal antibody (SBA) activity against NmA strains of immunotype L11 (F8238) and L10 (3125) and NmA-specific IgG. Seroprevalence was compared to the age-specific NmA meningitis incidence in Bobo-Dioulasso during March 2007-February 2008. Meningococcal carriage was evaluated in a subset (N = 538). Geometric mean titres (GMT)/concentrations (GMC) of SBA and NmA-specific IgG increased with age, peaking around age 20 years. Overall, 70% of our sample had NmA-specific IgG ≥2 ug/mL. Meningitis incidence was highest in those aged <6 months and 5-19 years. No NmA carriers were found. Compared to the reference strain SBA, GMTs were higher against a locally isolated strain and around 40-fold lower against Dutch strain 3125. CONCLUSIONS/SIGNIFICANCE: This study provides estimates of natural immunity to NmA, according to a variety of antibody measures, which will be helpful in ascertaining antibody persistence after MenAfriVac™ introduction. Age-specific seroprevalence of reference strain SBA titres most likely reflects exposure to meningococci and consecutive reactive immunity. We could not define any serological correlate of protection.

Pneumococcal serotype distribution among meningitis cases from Togo and Burkina Faso during 2007-2009.

We evaluated pneumococcal serotype/group distribution using polymerase chain reaction (PCR) testing on cerebrospinal fluid collected from patients from Burkina Faso and Togo who presented for care during 2007-2009. We identified 282 pneumococcal meningitis cases based on PCR, latex agglutination, or culture, of which 206 underwent serotyping. Serotype 1 was identified for 18% of serotyped cases from patients aged <5 years and 66% of those aged ≥5 years. The 13-valent and 10-valent pneumococcal conjugate vaccines (PCV-13 and PCV-10) contain 53% of serotypes identified among children age <5 years and 76-77% among persons aged ≥5 years. Pneumococcal meningitis was highly seasonal regardless of serotype. Data from this study emphasize the potential usefulness of PCVs among older children and adults.

Pneumococci in the African meningitis belt: meningitis incidence and carriage prevalence in children and adults.

BACKGROUND: The development of optimal vaccination strategies for pneumococcal conjugate vaccines requires serotype-specific data on disease incidence and carriage prevalence. This information is lacking for the African meningitis belt. METHODS: We conducted hospital-based surveillance of acute bacterial meningitis in an urban and rural population of Burkina Faso during 2007-09. Cerebrospinal fluid was evaluated by polymerase chain reaction for species and serotype. In 2008, nasopharyngeal swabs were obtained from a representative population sample (1 month to 39 years; N = 519) and additional oropharyngeal swabs from 145 participants. Swabs were evaluated by culture. RESULTS: Annual pneumococcal meningitis incidence rates were highest among <6-month-old (58/100,000) and 15- to 19-year-old persons (15/100,000). Annual serotype 1 incidence was around 5/100,000 in all age groups. Pneumococcal carriage prevalence in nasopharyngeal swabs was 63% among <5-year-old children and 22% among ≥5-year-old persons, but adding oropharyngeal to nasopharyngeal swabs increased the estimated carriage prevalence by 60%. Serotype 1 showed high propensity for invasive disease, particularly among persons aged ≥5 years. CONCLUSIONS: Serotype 1 causes the majority of cases with a relatively constant age-specific incidence. Pneumococcal carriage is common in all age groups including adults. Vaccination programs in this region may need to include older target age groups for optimal impact on disease burden.

Study of a localized meningococcal meningitis epidemic in Burkina Faso: incidence, carriage, and immunity.

BACKGROUND: To better understand localized meningococcal meningitis epidemics, we evaluated a serogroup A (NmA) epidemic in Burkina Faso by surveillance, carriage, and seroprevalence studies. METHODS: During March-April 2006, cerebrospinal fluid samples from patients suspected to have meningitis in 3 epidemic villages were analyzed by culture or polymerase chain reaction. We assessed meningococcal carriage and serogroup-specific serum bactericidal antibody titers with baby rabbit complement (rSBA) in a representative population sample (N = 624; age range, 1-39 years). A serogroup A/C polysaccharide vaccine campaign occurred in parallel. RESULTS: Cumulative incidence of Nm meningitis was 0.45% and varied among villages (0.08%-0.91%). NmA carriage prevalence was 16% without variation by vaccination status. NmA carriage and anti-NmA seroprevalence varied by village and incidence. In the 2 villages with highest incidence and seroprevalence, presence of rSBA titers ≥8 was associated with NmA carriage (odds ratio [OR], 9.33 [95% confidence interval {CI}, 1.90-45.91]) and vaccination ≤4 days earlier (OR, 0.10 [95% CI, .03-.32]). Visibly purulent or Nm meningitis was significantly associated with recent flulike symptoms and exposure to kitchen smoke (risk ratios >15). CONCLUSIONS: A surge of NmA carriage may be involved in the development of meningococcal epidemics and rapidly increase anti-NmA seroprevalence. Flulike infection and kitchen smoke may contribute to the strength of epidemics.

Emergence of epidemic Neisseria meningitidis serogroup X meningitis in Togo and Burkina Faso.

Serogroup X meningococci (NmX) historically have caused sporadic and clustered meningitis cases in sub-Saharan Africa. To study recent NmX epidemiology, we analyzed data from population-based, sentinel and passive surveillance, and outbreak investigations of bacterial meningitis in Togo and Burkina Faso during 2006-2010. Cerebrospinal fluid specimens were analyzed by PCR. In Togo during 2006-2009, NmX accounted for 16% of the 702 confirmed bacterial meningitis cases. Kozah district experienced an NmX outbreak in March 2007 with an NmX seasonal cumulative incidence of 33/100,000. In Burkina Faso during 2007-2010, NmX accounted for 7% of the 778 confirmed bacterial meningitis cases, with an increase from 2009 to 2010 (4% to 35% of all confirmed cases, respectively). In 2010, NmX epidemics occurred in northern and central regions of Burkina Faso; the highest district cumulative incidence of NmX was estimated as 130/100,000 during March-April. Although limited to a few districts, we have documented NmX meningitis epidemics occurring with a seasonal incidence previously only reported in the meningitis belt for NmW135 and NmA, which argues for development of an NmX vaccine.

Serotyping pneumococcal meningitis cases in the African meningitis belt by use of multiplex PCR with cerebrospinal fluid.

We reformulated a multiplex PCR algorithm for serotyping of pneumococcal meningitis directly on cerebrospinal fluid (CSF). Compared to established methods on isolates, CSF-based PCR had at least 80% sensitivity and 100% specificity. In regional meningitis surveillance, CSF-based PCR increased the serotype information yield from 40% of cases (isolate testing) to 90%.

The epidemiology of Neisseria meningitidis meningitis in Togo during 2003-2005.

Few reports documenting the epidemiology of Neisseria meningitidis (Nm) serogroup W135 exist, and none from Togo. During 2003-2005, we conducted acute bacterial meningitis surveillance at three major reference hospitals in Togo. Of 116 Nm identified, 83 (71%) were NmA, 23 (20%) were NmW135, and 10 (9%) did not have a serogroup identified. Nine percent of NmW135 cases and 35% of NmA cases occurred among those aged 15 years or older. The two hospitals in central Togo reported 23% of all Nm cases and 78% of NmW135 cases. Twelve of the 23 NmW135 cases occurred during February-March 2003, while the remaining 11 occurred sporadically over the remaining 18 months of the study. NmW135 meningitis showed pronounced temporal and geographic clustering and occurred almost exclusively among those younger than 15 years old. By the 2004-2005 epidemic season, NmW135 had largely disappeared from Togo for unknown reasons.

Epidemiological and molecular characteristics of a highly lethal pneumococcal meningitis epidemic in Burkina Faso.

BACKGROUND: Public health and clinical strategies for meningitis epidemics in sub-Saharan Africa usually assume that Neisseria meningitidis infection causes most disease. METHODS: During 24 months from 2002 to 2005, we collected clinical and laboratory information for suspected acute bacterial meningitis cases from 3 districts in Burkina Faso. Streptococcus pneumoniae was identified by culture, polymerase chain reaction, or antigen detection in cerebrospinal fluid. Pneumococcal genotyping was performed on strains using multilocus variable-number tandem repeat typing and multilocus sequence typing. RESULTS: Samples of cerebrospinal fluid were collected from 1686 persons; 249 (15%) had S. pneumoniae identified (annual incidence, 14 cases per 100,000 persons). Of these patients, 115 (46%) died, making S. pneumoniae the most commonly identified organism and responsible for two-thirds of deaths due to bacterial meningitis. During the meningitis epidemic season, an average of 38 cases of S. pneumoniae infection were identified each month, compared with an average of 8.7 cases during other months. Of 48 pneumococci that were tested, 21 (44%) were identified as serotype 1, and the remaining 27 (56%) were identified as 15 different serogroups and/or serotypes. Both serotype 1 and other serogroups and/or serotypes were seasonal. The genotypes of serotype 1 isolates were closely related but diversified over the study period and were similar to, but not identical to, the predominant genotypes found previously in Ghana. CONCLUSIONS: Intervention strategies during the epidemic season in Burkina Faso (and perhaps elsewhere) must now account for pneumococcal meningitis occurring in an epidemic pattern similar to meningococcal meningitis. Although a serotype 1 clone was commonly isolated, over half of the cases were caused by other serogroups and/or serotypes, and genetic diversification increased over a relatively short period.