Emergence of Unusual G6P[6] Rotaviruses in Children, Burkina Faso, 2009–2010

Johan Nordgren¹

, Leon W. Nitiema¹, Sumit Sharma, Djeneba Ouermi, Alfred S. Traore, Jacques Simpore, and Lennart Svensson

Author affiliations: Linköping University, Linköping, Sweden (J. Nordgren, S. Sharma, L. Svensson); Université de Ouagadougou, Ouagadougou, Burkina Faso (L.W. Nitiema, D. Ouermi, A.S. Traore, J. Simpore)

Abstract

To obtain more information about rotavirus (ROTAV) genotypes in Burkina Faso, we characterized 100 ROTAVs isolated from fecal samples of children with acute gastroenteritis in the capital city of Ouagadougou, during December 2009–March 2010. Of note, 13% of the ROTAV-positive samples, including those with mixed infections, were positive for the unusual G6 genotype ROTAV strain. The genotypes identified were G9P[8], G6P[6], G1P[6], G3P[6], G1P[8], and G2P[4]. G9P[8] subgroup (SG)II strains dominated during the beginning of the ROTAV season, but later in the season, other G types associated with P[6] and SGI specificity emerged. This emergence was related to a shift in the overall age of infected children; ROTAV SGII infected younger children and induced more severe symptoms. The finding of a high incidence of G6P[6] strains highlights the need for long-term surveillance of ROTAV strains in Burkina Faso, especially when ROTAV vaccination is being considered in several African countries.

Rotavirus (ROTAV) is a leading cause of severe acute gastroenteritis in infants and young children (1). It is estimated that ROTAV is responsible for 527,000 deaths each year; most occur in children from developing countries (2). More than 230,000 of these deaths occur in sub-Saharan Africa, and 6 of the 7 countries for which ROTAV diarrhea–related mortality rates are highest are located in Africa (2).
The viral protein (VP) 7 and VP4 genes encoding the 2 surface proteins form the basis of the current genotypic characterization of group A ROTAVs into G and P genotypes, respectively. At least 27 G genotypes and 35 P genotypes have been identified (3). Of these, 6 ROTAV G-P combinations (G1P[8], G2P[4], G3P[8], G4P[8], G9P[8], and G9P[6]) are common worldwide (4–6); several other combinations occur at low frequencies, and a few others occur mainly in animals (7,8). On the basis of molecular and immunological analysis, the VP6 gene has been classified into 2 subgroups (SGI and SGII); SGII is the most prevalent among humans (9,10) and SGI is more commonly found in animals (11).
The G-P combinations circulating in Africa often differ from those circulating in other parts of the world (12). A review of studies in Africa published during 1997–2006 showed that the most common G and P type combinations were G1P[8] (17.4%), G2P[6] (9.6%), G8P[6] (9.4%), and G3P[8] (7%) (13). A study from West Africa, covering 1996–2000, found that G1P[6] was the most common G-P combination, followed by G2P[6] and G9P[8] (12). During 1998–2000, the G9P[8] combination was the most prevalent genotype in northern Ghana (14). However, many ROTAV strains isolated in Africa still remain to be characterized for G and/or P type (13).
Although bovine G6 ROTAV strains are the predominant genotype in cattle in Africa, G6 infection in humans has rarely been described; however, sporadic cases of G6 in humans in combination with P[14] and P[9] have been described (15–21). P[6] is a commonly observed P type, especially in Africa. However, to our knowledge, the literature reports only once the isolation of strain G6P[6] in Belgium, from a child returning from a trip to Mali (22).
In Burkina Faso, previous studies have shown ROTAV to be the main cause of diarrhea in children (23–26), but limited molecular information exists about the circulating genotypes. The first molecular characterization of ROTAVs, which was conducted on samples from 1999, showed a predominance of unusual G2P[6]SGI strains (27).
In this study, we determined the G and P genotypes of ROTAVs isolated from children with acute gastroenteritis in Ouagadougou, the capital of Burkina Faso, during the cold, dry season of December 2009–March 2010. We found that G6P[6] ROTAV strains were the second most common genotype circulating; incidence was 13%. We discuss the emergence of this most unusual genotype in association with vaccine efficacy and zoonotic transfer.