Neisseria meningitidis Serogroup W, Burkina Faso, 2012

Jessica R. MacNeil

, Isaïe Medah, Daouda Koussoubé, Ryan T. Novak, Amanda C. Cohn, Fabien V.K. Diomandé, Denis Yelbeogo, Jean Ludovic Kambou, Tiga F. Tarbangdo, Rasmata Ouédraogo-Traoré, Lassana Sangaré, Cynthia Hatcher, Jeni Vuong, Leonard W. Mayer, Mamoudou H. Djingarey, Thomas A. Clark, and Nancy E. Messonnier

Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (J.R. MacNeil, R.T. Novak, A.C. Cohn, F.V.K. Diomandé, C. Hatcher, J. Vuong, L.W. Mayer, T.A. Clark, N.E. Messonnier); Ministère de la Santé, Ouagadougou, Burkina Faso (I. Medah, D. Koussoubé, D. Yelbeogo, J.L. Kambou, T.F. Tarbangdo);WHO Intercountry Support Team for West Africa, Ouagadougou (F.V.K. Diomandé, M.H. Djingarey); Centre Hospitalier Universitaire Pédiatrique Charles de Gaulle, Ouagadougou (R. Ouédraogo-Traoré); Centre Hospitalier Universitaire Yalgado, Ouagadougou (L. Sangaré)

Abstract

In 2010, Burkina Faso became the first country to introduce meningococcal serogroup A conjugate vaccine (PsA-TT). During 2012, Burkina Faso reported increases in Neisseria meningitidis serogroup W, raising questions about whether these cases were a natural increase in disease or resulted from serogroup replacement after PsA-TT introduction. We analyzed national surveillance data to describe the epidemiology of serogroup W and genotyped 61 serogroup W isolates. In 2012, a total of 5,807 meningitis cases were reported through enhanced surveillance, of which 2,353 (41%) were laboratory confirmed. The predominant organism identified was N. meningitidis serogroup W (62%), and all serogroup W isolates characterized belonged to clonal complex 11. Although additional years of data are needed before we can understand the epidemiology of serogroup W after PsA–TT introduction, these data suggest that serogroup W will remain a major cause of sporadic disease and has epidemic potential, underscoring the need to maintain high-quality case-based meningitis surveillance after PsA–TT introduction.

In Burkina Faso, which lies within the meningitis belt of sub-Saharan Africa, rates of endemic meningitis are high, seasonal epidemics occur each year, and explosive epidemics occur every 5–12 years (1,2). Historically, these epidemics have been caused primarily by Neisseria meningitidis serogroup A (3,4). During late 2010, Burkina Faso became the first country to introduce a novel meningococcal serogroup A polysaccharide–tetanus toxoid conjugate vaccine (PsA-TT, MenAfriVac (Serum Institute of India Ltd, Pune, India). More than 11 million persons were vaccinated during ≈10 days in the eligible population of persons aged 1–29 years (4,5). Early evidence suggests that this aggressive strategy substantially reduced the rate of meningitis among persons in these age groups and in the general population because of high coverage and herd immunity (5). Since 2010, nine countries have implemented PsA-TT; the 100 millionth dose was given in December 2012.

Although N. meningitidis serogroup A has virtually disappeared in countries that have implemented nationwide vaccination campaigns, other serogroups, including N. meningitidisserogroup W and serogroup X, have the potential to cause epidemics. Sporadic disease and localized epidemics caused by serogroup X have been well described, but the potential of serogroup X to cause large epidemics remains unclear (6). During 2000 and 2001, serogroup W was associated with outbreaks in pilgrims to the Hajj and was followed by several clusters of cases worldwide (7–9). The largest reported outbreak caused by serogroup W occurred in Burkina Faso in 2002 and comprised ≈13,000 suspected cases (10). Sporadic cases and smaller outbreaks caused by serogroup W have continued to occur and have been described as occurring in several meningitis belt countries, including Burkina Faso (11–15). During 2012, Burkina Faso reported an increase in cases of serogroup W, raising questions about whether the increase resulted from a natural increase in disease or resulted from serogroup replacement after PsA-TT introduction. We analyzed national surveillance data and isolates from Burkina Faso to describe the epidemiology of serogroup W during 2012 and to assess changes and trends in serogroup W epidemiology around PsA-TT introduction.