Prevalence and epidemiology of meningococcal carriage in Southern Ethiopia prior to implementation of MenAfriVac, a conjugate vaccine.

Guro K Bårnes,Marie-Pierre Préziosi,Paulos Fissiha,Jon Bohlin,Paul A Kristiansen,Demissew Beyene,Behailu Merdekios,Abraham Aseffa,Bereket Workalemahu,Dominique A Caugant

doi:10.1186/s12879-016-1975-3

Abstract

Background Neisseria meningitidis colonizes humans and transmits mainly by asymptomatic carriage. We sought to determine the prevalence and epidemiology of meningococcal carriage in Ethiopia prior to the introduction of MenAfriVac, a serogroup A meningococcal conjugate vaccine.MethodsA cross-sectional meningococcal carriage study was conducted in Arba Minch, southern Ethiopia. A total of 7479 oropharyngeal samples were collected from 1 to 29 year old volunteers, between March and October, 2014. The swabs were cultured for N. meningitidis and Neisseria lactamica in Ethiopia. N. meningitidis isolates were confirmed and characterized by their serogroup, sequence type (ST) and PorA:FetA profile in Norway.ResultsOverall carriage prevalence was 6.6 %. There was no significant difference in overall carriage between male (6.7 %) and female (6.4 %) participants. Highest carriage prevalence (10.9 %) for females was found in the 15–19 years of age, while prevalence among males was highest (11.3 %) in the 20–24 age group. Non-groupable isolates dominated (76.4 %), followed by serogroups X (14.0 %) and W (5.9 %) isolates. No serogroup A was found. Most non-groupable isolates were ST-192. Serogroup W isolates were assigned to the ST-11 clonal complex, and serogroup X isolates to the ST-181 and ST-41/44 clonal complexes. Overall carriage prevalence of N. lactamica was 28.1 %. Carriage of N. meningitidis and N. lactamica varied depending on age and geographic area, but there was no association between carriage of the two species.ConclusionsEpidemic strains of serogroups W and X were circulating in this area of Ethiopia. As no serogroup A was found among the carriage isolates the immediate impact of mass-vaccination with MenAfriVac on transmission of N. meningitidis in this population is expected to be marginal.

Highlights

Neisseria meningitidis colonizes humans and transmits mainly by asymptomatic carriage
We present here the epidemiology and molecular characterization of meningococcal carriage isolates retrieved from 7479 children and young adults living in southern Ethiopia, immediately before the introduction of MenAfriVac
The true carriage prevalence in the Conclusions No N. meningitidis belonging to serogroup A was detected among 7479 healthy carriers in the Arba Minch area in Ethiopia in 2014

Summary

Introduction

Neisseria meningitidis colonizes humans and transmits mainly by asymptomatic carriage. The meningococcus, is a commensal microorganism colonizing the upper respiratory tract, usually without causing disease. Meningococci are found only in humans and the bacterium is transmitted mainly through close contact and airborne droplets. But is usually around 5–10 % [1, 2]. In crowded or contained societies, such as universities, carriage prevalence can be significantly higher [3, 4]. Carriage prevalence is usually found to be higher in males than females. Living conditions and social behavior, such as active and passive smoking [6], discotheque visits and crowding [7], are among the known risk factors for carriage

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