Phenotypic and genotypic characterization of meningococcal carriage and disease isolates in Burkina Faso after mass vaccination with a serogroup a conjugate vaccine

Paul A Kristiansen,Denis Kandolo,Rasmata Ouédraogo,Thomas A Clark,Dominique A Caugant,Abdoul-Salam Ouédraogo,Idrissa Sanou,Fabien Diomandé,Jennifer Dolan Thomas,Marc Laforce,Absatou Ky Ba,Lassana Sangaré

doi:10.1186/1471-2334-13-363

Abstract

BackgroundThe conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010. The aim of this study was to genetically characterize meningococcal isolates circulating in Burkina Faso before and up to 13 months after MenAfriVac mass vaccination.MethodsA total of 1,659 meningococcal carriage isolates were collected in a repeated cross-sectional carriage study of the 1-29-year-olds in three districts of Burkina Faso in 2010 and 2011, before and up to 13 months after mass vaccination. Forty-two invasive isolates were collected through the national surveillance in Burkina Faso in the same period. All the invasive isolates and 817 carriage isolates were characterized by serogroup, multilocus sequence typing and porA-fetA sequencing.ResultsSeven serogroup A isolates were identified, six in 2010, before vaccination (4 from carriers and 2 from patients), and one in 2011 from an unvaccinated patient; all were assigned to sequence type (ST)-2859 of the ST-5 clonal complex. No NmA carriage isolate and no ST-2859 isolate with another capsule were identified after vaccination. Serogroup X carriage and disease prevalence increased before vaccine introduction, due to the expansion of ST-181, which comprised 48.5% of all the characterized carriage isolates. The hypervirulent serogroup W ST-11 clone that was responsible for most of meningococcal disease in 2011 and 2012 was not observed in 2010; it appeared during the epidemic season of 2011, when it represented 40.6% of the serogroup W carriage isolates.ConclusionsSuccessive clonal waves of ST-181 and ST-11 may explain the changing epidemiology in Burkina Faso after the virtual disappearance of NmA disease and carriage. No ST-2859 strain of any serogroup was found after vaccination, suggesting that capsule switching of ST-2859 did not occur, at least not during the first 13 months after vaccination.

Highlights

The conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010
In the African meningitis belt, a sub-Saharan region stretching from Senegal to Ethiopia [1,2], the populations are affected by annual outbreaks of meningococcal meningitis during the dry season
In 2006 a major serogroup X epidemic caused by sequence types (ST)-181 affected the neighbouring country Niger [11,12] and the clone later spread to Burkina Faso [13]

Summary

Introduction

The conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010. The aim of this study was to genetically characterize meningococcal isolates circulating in Burkina Faso before and up to 13 months after MenAfriVac mass vaccination. Burkina Faso, a West-African country of approximately 16 million inhabitants, is among the most affected ones, and NmA of sequence types (ST), ST-7 and ST-2859 have been successively responsible for major epidemics [4,6]. In 2006 a major serogroup X epidemic caused by ST-181 affected the neighbouring country Niger [11,12] and the clone later spread to Burkina Faso [13]

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