Rotavirus genotypes circulating in Ontario, Canada, before and after implementation of the rotavirus immunization program

BACKGROUND AND OBJECTIVES

Ontario introduced a universal publicly-funded group A rotavirus (RVA) immunization program in August 2011, using monovalent vaccine. RVA immunization programs have decreased the incidence of RVA acute gastroenteritis in many countries but it is unclear if it will contribute to the emergence of certain genotypes. We monitored RVA trends and genotypes in Ontario before and after implementation of the publicly-funded immunization program.

METHODS

RVA detection was conducted at Public Health Ontario Laboratories from January 2009 to December 2011 (pre-program period) and January 2012 to October 2015 (publicly-funded RVA immunization program period) and number of RVA-positive specimens and percent positivity were analysed. A convenience sample of RVA-positive stool specimens, from September 2010 to December 2011 (pre-program period) and January 2012 to June 2013 (program period), were genotyped using heminested PCR. A literature review on the burden of illness from emergent genotype was performed.

RESULTS

Stool specimens showed a significant decrease in RVA percent positivity from the 36 month pre-program period (14.4%; 1537/10700) to the 46 month program period (6.1%; 548/9019). An increase in the proportion of RVA G10 among genotyped specimens, associated with five different P genotypes, from the pre-program (6.3%; 13/205) to the program (31.5%; 40/127) period was observed. Our literature review identified approximately 200 G10-positive human stool specimens from 16 different countries.

CONCLUSIONS

This study documented a decrease in the number of RVA-positive specimens and percent positivity after implementation of the immunization program. An unexpected increase in the proportion of RVA G10 was detected following program introduction. Ongoing RVA surveillance is important in evaluating both the long-term impact of immunization and emergence of RVA genotypes.

Molecular epidemiology of Rotavirus A, causing acute gastroenteritis hospitalizations among children in Nha Trang, Vietnam, 2007-2008: Identification of rare G9P[19] and G10P[14] strains

Rotavirus A (RVA) causes acute diarrhea in children as well as animals. As part of a cross-sectional study of children less than 5 years of age hospitalized for acute diarrhea in Vietnam during a 15-month period (2007-2008), 322 (43.5%) of 741 fecal specimens contained RVA with 92% either G1P[8] or G3P[8]. This study was undertaken to further characterize strains that remained untypeable to complete the G and P genotypes of the 322 rotavirus-positive specimens. While 307 (95.3%) strains possessed the common human RVA genotypes: G1P[8] (45.0%), G2P[4] (2.8%), G3P[8] (46.9%), and G9P[8] (0.6%), sequencing of initially untypeable specimens revealed the presence of two unusual strains designated NT0073 and NT0082 possessing G9P[19] and G10P[14], respectively. The genotype constellation of NT0073 (G9-P[19]-I5-R1-C1-M1-A8-N1-T7-E1-H1) and the phylogenetic trees suggested its origin as a porcine RVA strain causing diarrhea in a 24-month-old girl whereas the genotype constellation of NT0082 (G10-P[14]-I2-R2-C2-M2-A3-N2-T6-E2-H3) and the phylogenetic trees suggested its origin as an RVA strain of artiodactyl origin (such as cattle, sheep and goats) causing diarrhea in a 13-month-old boy. This study showed that RVA strains of animal host origin were not necessarily attenuated in humans. A hypothesis may be postulated that P[19] and P[14] VP4 spike proteins helped the virus to replicate in the human intestine but that efficient onward human-to-human spread after crossing the host species barrier may require the virus to obtain some additional features as there was no evidence of widespread transmission with the limited sampling performed over the study period. J. Med. Virol. 89:621-631, 2017. © 2016 Wiley Periodicals, Inc.