Measles Virus Strain Diversity, Nigeria and DRC | CDC EID

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Volume 16, Number 11–November 2010
Research
Measles Virus Strain Diversity, Nigeria and Democratic Republic of the Congo

Jacques R. Kremer, Edith Nkwembe, Akeeb O. Bola Oyefolu, Sheilagh B. Smit, Elisabeth Pukuta, Sunday A. Omilabu, Festus D. Adu, Jean-Jacques Muyembe Tamfum, and Claude P. Muller Comments to Author
Author affiliations: Centre de Recherche Publique–Santé/Laboratoire National de Santé, Luxembourg, Luxembourg (J.R. Kremer, C.P. Muller); Institut National de Recherche Biomédicale, Kinshasa, Democratic Republic of the Congo (E. Nkwembe, E. Pukuta, J.-J.M. Tamfum); Lagos State University, Lagos, Nigeria (A.O.B. Oyefolu); National Institute for Communicable Diseases, Johannesburg, South Africa (S.B. Smit); University of Lagos, Lagos (S.A. Omilabu); and University of Ibadan, Ibadan, Nigeria (F.D. Adu)

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Abstract
We investigated the genetic diversity of measles virus (MV) in Nigeria (2004–2005) and the Democratic Republic of the Congo (DRC) (2002–2006). Genotype B3 strains circulating in Kinshasa, DRC, in 2002–2003 were fully replaced by genotype B2 in 2004 at the end of the second Congo war. In Nigeria (2004–2005), two genetic clusters of genotype B3, both of which were most closely related to 1 variant from 1998, were identified. Longitudinal analysis of MV strain diversity in Nigeria suggested that only a few of the previously described 1997–1998 variants had continued to circulate, but this finding was concomitant with a rapid restoration of genetic diversity, probably caused by low vaccination coverage and high birth rates. In contrast, the relatively low genetic diversity of MV in DRC and the genotype replacement in Kinshasa reflect a notable improvement in local measles control.

Despite >90% reduction in the annual measles mortality rate in the World Health Organization (WHO) African Region during 2000–2006 (1), measles remains a major cause of deaths in children in sub-Saharan Africa (2,3). During this period, routine coverage of measles-containing vaccines increased from 56% to 73% in this region, and >200 million children were vaccinated through supplementary immunization activities (SIAs) by December 2004 (4). In the Democratic Republic of the Congo (DRC), vaccination coverage with a first dose of measles vaccine increased from 46% in 2000 to 70% in 2005, according to official country reports (5). The first major catch-up campaigns were conducted in several provinces in 2002 (Kasaï Oriental, Nord Kivu) and 2004 (Kasaï Occidental, Maniema, Katanga, Maniema, Sud-Kivu) (6). In Nigeria, no SIAs took place until 2005, and routine vaccination coverage was persistently low (<40%), at least until 2006 (3,5,7). Molecular epidemiology has proven to be a major component of measles surveillance because it enables the effect of accelerated measles control activities to be assessed and the elimination of endemic virus strains to be documented. In Africa, indigenous measles virus (MV) genotypes seem to have a distinct geographic distribution (8,9). In the central and western parts of sub-Saharan Africa, mainly clade B viruses have been identified (10–17). The most common genotype is B3, with its 2 clusters B3.1 and B3.2 (10). The first B3 sequences in Africa were reported from Nigeria (1997–1998). The 41 MV isolates collected in southwestern Nigeria clustered in 2 distinct subgroups of genotype B3 (B3.1 and B3.2), with an unprecedented maximal sequence diversity of 4.6% in the C-terminus of the MV nucleoprotein hypervariable region (MVN-HVR) (10). In the eastern and southern parts of Africa, genotypes D2 and D4 dominated and a new genotype (D10) was detected in Uganda in 2000 (8,9,18). Although MV sequence data from Africa have been greatly expanded since characterization of the first endemic strains was reported (8,10,17,19), essential genetic baseline information is still missing from many countries (20). For instance, from DRC, only 5 genotype B3 sequences have been reported from Kinshasa (2000) (15). We characterized MV strains collected during 2002 through 2006 from different locations throughout DRC and Nigeria. A comparison of the genetic diversity of MV strains showed notable differences in epidemiologic patterns in both countries that can be only partially explained by differences in vaccination practices. full-text: Measles Virus Strain Diversity, Nigeria and DRC | CDC EID

Suggested Citation for this Article

Kremer JR, Nkwembe E, Oyefolu AOB, Smit SB, Pukuta E, Omilabu SA, et al. Measles virus strain diversity, Nigeria and Democratic Republic of the Congo. Emerg Infect Dis [serial on the Internet]. 2010 Nov [date cited].
http://www.cdc.gov/EID/content/16/11/1724.htm

DOI: 10.3201/eid1611.100777