Rotavirus strain diversity in Eastern and Southern African countries before and after vaccine introduction

BACKGROUND

The African Rotavirus Surveillance Network has been detecting and documenting rotavirus genotypes in the African sub-continent since 1998 in anticipation of the rollout of rotavirus vaccination in routine Expanded Programme on Immunisation. This paper reports distribution of the rotavirus strains circulating in 15 Eastern and Southern African (ESA) countries from 2010-2015 as part of active World Health Organization (WHO) rotavirus surveillance, and investigates possibility of emergence of non-vaccine or unusual strains in six selected countries post-vaccine introduction.

MATERIAL AND METHODS

Stool samples were collected from children <5 years of age presenting with acute gastroenteritis at sentinel hospitals pre- and post-rotavirus vaccine introduction. Samples were tested for group A rotavirus using an enzyme immunoassay by the national and sentinel laboratories. At the WHO Rotavirus Regional Reference Laboratory in South Africa, molecular characterisation was determined by PAGE (n = 4186), G and P genotyping (n = 6447) and DNA sequencing for both G and P types (n = 400).

RESULTS

The six-year surveillance period demonstrated that 23.8% of the strains were G1P[8], followed by G2P[4] (11.8%), G9P[8] (10.4%), G12P[8] (4.9%), G2P[6] (4.2%) and G3P[6] (3.7%) in 15 ESA countries. There was no difference in circulating strains pre- and post-rotavirus vaccine introduction with yearly fluctuation of strains observed over time. Atypical rotavirus G and P combinations (such as G1P[4], G2P[8], G9P[4] and G12P[4]) that might have arisen through inter-genogroup or inter-genotypes reassortment were detected at low frequency (2%). Close genetic relationship of African strains were reflected on the phylogenetic analysis, strains segregated together to form an African cluster in the same lineages/sub-lineage or monophyletic branch.

CONCLUSION

There has been considerable concern about strain replacement post-vaccine introduction, it was not clear at this early stage whether observed cyclical changes of rotavirus strains were due to vaccine pressure or this was just part of natural annual fluctuations in the six ESA countries, long-term surveillance is required.

Temporal association of rotavirus vaccination and genotype circulation in South Africa: Observations from 2002 to 2014

BACKGROUND

Rotavirus vaccination has reduced diarrhoeal morbidity and mortality globally. The monovalent rotavirus vaccine was introduced into the public immunization program in South Africa (SA) in 2009 and led to approximately 50% reduction in rotavirus hospitalization in young children. The aim of this study was to investigate the rotavirus genotype distribution in SA before and after vaccine introduction.

MATERIALS AND METHODS

In addition to pre-vaccine era surveillance conducted from 2002 to 2008 at Dr George Mukhari Hospital (DGM), rotavirus surveillance among children <5 years hospitalized for acute diarrhoea was established at seven sentinel sites in SA from April 2009 to December 2014. Stool specimens were screened by enzyme immunoassay and rotavirus positive specimens genotyped using standardised methods.

RESULTS

At DGM, there was a significant decrease in G1 strains from pre-vaccine introduction (34%; 479/1418; 2002-2009) compared to post-vaccine introduction (22%; 37/170; 2010-2014; p for trend <.001). Similarly, there was a significant increase in non-G1P[8] strains at this site (p for trend <.001). In expanded sentinel surveillance, when adjusted for age and site, the odds of rotavirus detection in hospitalized children with diarrhoea declined significantly from 2009 (46%; 423/917) to 2014 (22%; 205/939; p<.001). The odds of G1 detection declined significantly from 2009 (53%; 224/421) to 2010-2011 (26%; 183/703; aOR=0.5; p<.001) and 2012-2014 (9%; 80/905; aOR=0.1; p<.001). Non-G1P[8] strains showed a significant increase from 2009 (33%; 139/421) to 2012-2014 (52%; 473/905; aOR=2.5; p<.001).

CONCLUSIONS

Rotavirus vaccination of children was associated with temporal changes in circulating genotypes. Despite these temporal changes in circulating genotypes, the overall reduction in rotavirus disease in South Africa remains significant.

A first report on the characterization of rotavirus strains in Sierra Leone

In an effort to reduce the high mortalities associated with rotavirus infections, a number of African countries are considering introducing human rotavirus vaccines. The demonstrated safety and efficacy of the live-attenuate human rotavirus vaccines in several clinical trials worldwide has accelerated such initiatives. Although the percentage-mortality rates for Sierra Leone are top of the list for rotavirus-associated deaths in Africa, no study has reported the prevalent strains circulating within this country. In this study, stool specimens were collected from 128 Sierra Leonean children presenting with diarrhea in 2005. Almost 37.5% (48/128) were rotavirus positive by EIA, of which 89.6% (43/48) revealed a short electropherotype, and a further 6.98% (3/48) could not be assigned a PAGE pattern. Genotyping analysis revealed G2P[4] (30.23%), G2P[6] (13.95%), G8P[6] (11.63%), G2P[8] (4.65%), G8P[4] (4.65%), and G8P[8] (2%) strains. About 11% were only assigned VP7 genotypes (G2), while 20.9% had mixed G and P types. The frequent detection of G2 rotaviruses could be of concern considering data generated from some studies that suggests lower efficacy of Rotarix® vaccine against G2 rotaviruses. This underscores the need for extensive and continuous regional strain surveillance to support rotavirus vaccines introduction and guide future vaccine development efforts. Such information will be useful before considering administration of specific rotavirus vaccine candidates in countries like Sierra Leone where little is known about circulating rotavirus strains.

Characterization and molecular epidemiology of rotavirus strains recovered in Northern Pretoria, South Africa during 2003-2006

Rotavirus infection is the most common cause of severe dehydrating gastroenteritis in infants and young children and remains a significant clinical problem worldwide. The severity and the burden of rotavirus disease could be reduced through the implementation of an effective vaccine. The aim of this study was to characterize rotavirus strains circulating in the local community as part of an ongoing hospital burden of disease study when a G1P[8] rotavirus vaccine candidate was being evaluated in the same community. From 2003 through 2006, 729 rotavirus-positive stool specimens were collected from children <5 years of age who were treated for diarrhea at Dr George Mukhari Hospital, Ga-Rankuwa, South Africa. Molecular characterization of the strains was performed by polyacrylamide gel electrophoresis and genotyping of the VP4 and VP7 alleles using well-established seminested multiplex reverse-transcription polymerase chain reaction methods. In 2003, 62% of strains exhibited the short rotavirus electropherotype, and the most common rotavirus strain was G2P[4]. In subsequent years, predominant rotavirus strains included G1P[8] and G1P[6] in 2004, G3P[8] and G3P[6] in 2005, and G1P[8] in 2006. For the 4 years of the study, rotavirus strains with P[6] genotype were detected in 25% of all rotavirus-positive specimens. In addition, unusual G12P[6] and G8 strains were detected at a low frequency. These results reflect the diversity of rotavirus strains circulating in South African communities.

Burden and epidemiology of rotavirus diarrhea in selected African countries: preliminary results from the African Rotavirus Surveillance Network

Severe rotavirus diarrhea in children <5 years of age is a major public health problem; however, limited regional and country specific data on rotavirus disease burden are available from sub-Saharan Africa. In June 2006, the World Health Organization Regional Office for Africa initiated rotavirus surveillance in selected African countries. With use of standardized methodology developed by the World Health Organization, children <5 years of age who were hospitalized with severe diarrhea were enrolled, and stool specimens were collected for detection of rotavirus strains with use of a commercial enzyme immunoassay. Rotavirus strains were further characterized for G and P types with use of a reverse-transcriptase polymerase chain reaction. From June 2006 through December 2008, rotavirus surveillance was established at 14 sites in 11 African countries. Of 5461 stool samples collected from children enrolled in 8 countries with 1 or 2 complete years of data, 2200 (40%) were positive for rotavirus. Ninety percent of all rotavirus hospitalizations occurred among children aged 3-12 months. Predominant types included G1P[8] (21%), G2P[4] (7%), and P [8] (29%); however, unusual types were also detected, including G8P[6] (5%), G8P[8] (1%), G12P[6] (1%), and G12P[6] (1%). A high percentage of mixed rotavirus infections was also detected. These preliminary results indicate that rotavirus is a major cause of severe diarrheal disease in African children.