Distribution of rotavirus genotypes associated with acute diarrhoea in Zimbabwean children less than five years old before and after rotavirus vaccine introduction

Abstract

Background: Sentinel surveillance for diarrhoea is important to monitor changes in rotavirus epidemiological trends and circulating genotypes among children under 5 years before and after vaccine introduction. The Zimbabwe Ministry of Health and Child Care introduced rotavirus vaccine in national immunization program in May 2014.

Methods: Active hospital-based surveillance for diarrhoea was conducted at 3 sentinel sites from 2008 to 2016. Children aged less than 5 years, who presented with acute gastroenteritis as a primary illness and who were admitted to a hospital ward or treated at the emergency unit, were enrolled and had a stool specimen collected and tested for rotavirus by enzyme immunoassay (EIA). Genotyping of positive stools was performed using reverse-transcription polymerase chain reaction and genotyping assays. Pre-vaccine introduction, 10% of all positive stool specimens were genotyped and all adequate positive stools were genotyped post-vaccine introduction.

Results: During the pre-vaccine period, a total of 6491 acute gastroenteritis stools were collected, of which 3016 (46%) tested positive for rotavirus and 312 (10%) of the rotavirus positive stools were genotyped. During the post-vaccine period, a total of 3750 acute gastroenteritis stools were collected, of which 937 (25%) tested positive for rotavirus and 784 (84%) were genotyped. During the pre-vaccine introduction the most frequent genotype was G9P[8] (21%) followed by G2P[4] (12%), G1P[8] (6%), G2P[6] (5%), G12P[6] (4%), G9P[6] (3%) and G8P[4] (3%). G1P[8] (30%) was most dominant two years after vaccine introduction followed by G9P[6] (20%), G2P[4] (15%), G9P[8] (11%) and G1P[6] (4%).

Conclusion: The decline in positivity rate is an indication of early vaccine impact. Diversity of circulating strains underscores the importance of continued monitoring and strain surveillance after vaccine introduction.

Keywords: Genotypes vaccine; Rotavirus; Surveillance; Zimbabwe.

Figure 1a:

Circulating G-types:2008-2016

Figure 1b:

Circulating P-types:2008-2016

Figure 1c:

Circulating combined G&P genotypes;2008-2016

Figure 2:

Percentages of circulating rotavirus G- genotypes before and after introduction of rotavirus vaccine

Figure 3:

Percentages of circulating rotavirus P-genotypes before and after introduction of rotavirus vaccine

Figure 4a:

VP7 phylogenetic tree of Zimbabwe G1, G2 and G9 rotavirus strains constructed with neighbour-joining method. The phylogenetic tree was constructed with 1000 bootstrap replicates and only values >50 are shown. The clustalW alignment was built with more or less 981 nucleotide base pairs. The studied strains represented by a filled triangle.

Figure 4b:

VP4 phylogenetic tree of Zimbabwe P[4], P[6] and P[8] strains based on VP8* region with more or less 896 nucleotide based pairs. Phylogenetic tree was constructed using neighbour-joining method in MEGA6. Bootstraps replicates of 1000 were calculated and only bootstraps >50 are shown. The studied strains represented with a filled triangle.