Location of the study:
Epidemiogy Unit, Department of Public health, Ministry of Health, Birnin Kebbi, Kebbi State
Background: Cerebrospinal meningitis (CSM), is a major public health problem still affecting tropical countries particularly in sub-Saharan Africa. Group A and occasionally group C account for large scale epidemics in many countries in the African meningitis belt. The study aimed to describe the pattern of cerebrospinal meningitis outbreak in Kebbi state in 2015.
Method: Information on cases and deaths was collected throughout the duration of the meningitis outbreak in all affected local government areas of Kebbi state. During this outbreak, we defined a suspected case as any person with sudden onset of fever (>38.5 C rectal or 38.0 C axillary) and one of the following signs: neck stiffness, altered consciousness or other meningeal signs and any toddler with sudden onset of fever (>38.5 C rectal or 38.0 C axillary) and one of the following signs: neck stiffness, or flaccid neck, bulging fontanel, convulsion or other meningeal signs. All the data was entered into SPSS statistical software and analyzed.
Results: A total of 1,992 suspected cases of CSM were seen within the 18 weeks that the outbreak lasted. 1127 (57.0%) were males and 865 (43.0%) were females with a case fatality rate of 4.0%. The highest proportion of cases was found among those above 15 years of age (31.0%), 1252 (62.9%) of cases were immunized against neisseria meningitides type A. Two-thirds (16) of the LGAs in the state were affected and Aliero LGA had about half (n=1106; 55.5%) of cases seen. Most (77.3%) of samples analysed were positive for Nm type C.
Conclusion: Kebbi state experienced an outbreak of cerebro-spinal Meningitis in 2015 which was massive. This was due to lack of herd immunity against the causative serogroup (NmC). Effective surveillance system and mass vaccination with polyvalent vaccines containing serogroup C will prevent future occurrence.
Keywords: Meningitis belt, MenAfriVac, Neisseria meningitidis type C, Sub-Saharan Africa
Cerebrospinal meningitis, also called epidemic meningococcal meningitis, is a major public health problem still affecting tropical countries, particularly in sub-Saharan Africa. It is highly contagious and mortality from the disease remains high, despite major achievements in the treatment modalities. It is reported that 4 – 17% of patients die despite treatment.1, 2 Neisseria meningitidis has 13 known serotypes worldwide with groups A, B and C being the commonest cause of diseases worldwide.3 Groups A, B, C, Y, and W-135 are responsible for most of invasive disease in both developed and developing countries, whereas, group A and occasionally group C account for large scale epidemics in many countries particularly in sub-Saharan Africa.4, 5 The African meningitic belt region comprises of 25 countries stretching from Senegal to Ethiopia with a total population of about 500 million people).6
In the African meningitis belt, and specifically within northern Nigeria, most meningitis outbreaks have been caused by N. meningitides serogroup A (NmA).2, 7-10 A particularly severe epidemic of meningococcal meningitis occurred in Nigeria between January and June 1996, with 109,580 recorded cases and 11,717 deaths, with a case fatality rate of 10.7%. This was the most serious epidemic of CSM ever recorded in Nigeria, and may be the largest in Africa this century.11 It took over 3 months and the combined efforts of a National Task Force set up by the Federal Ministry of Health, the World Health Organization (WHO), United Nations Children Fund (UNICEF), United Nations Development Fund (UNDP), Médecins Sans Frontières (MSF), the International Red Cross and several other non-governmental organizations to bring the epidemic under control.11
Nigeria with support from the Global Alliance for Vaccine Initiative (GAVI) introduced MenAfriVac– a vaccine which protects against the most prevalent type of Nm serogroup A. Mass campaigns was carried out in all CSM high risk states including Kebbi state with the expectation that it would prevent more than 150,000 deaths by 2015 as well as avoid significant disability and have considerable economic benefits.6
In the past 15 years, there has been increasing number of large outbreaks caused by N. meningitidis serogroups W135 and X in Niger, Burkina faso and northern Ghana.7 Outbreaks due to Neisseria meningitidis serogroup C (NmC) have also occurred but were smaller and less frequent than NmA outbreaks.2, 10 The last NmC outbreak in this region occurred in 1979 in Burkina Faso with 539 cases reported (attack rate (AR) 517/100,000).7 Outbreaks caused by NmC in northern Nigeria are rare, with the last and only recorded outbreak in 1975 with no detailed report published. Other notable NmC outbreaks occurred in the 1970s in Sao Paulo, Brazil and Ho Chi Minh, Vietnam with 2005 (11/100,000 people) and 1015 (>20/100,000 people) cases respectively.7 In the USA, morbidity and mortality are higher among young adults in outbreaks caused by NmC compared with other serogroups.7
Nigeria has not recorded any major outbreak of meningitis since 2012 because of the introduction of MenAfriVac vaccine in December 2011. In 2011, 7.4 million eligible Nigerians were immunized, in 2012 another 7.5 million and in 2013 yet another 7.8 million. Because of this, no major outbreak of meningitis has been experienced. The vaccination offers a minimum of 10 years protection to maximum of lifelong protection.6 In response to meningitis A (NmA) outbreak that occurred in Sokoto and Kebbi states between 2008 and 2009, Médecins sans Frontières (MSF) conducted reactive vaccination using polysaccharide ACYW135 vaccine.7 There has been no mass vaccination specifically targeting NmC alone in this region.7 This paper describes the general characteristics of an outbreak due to a strain of NmC in Kebbi State, Nigeria in 2015.