Review of rotavirus studies in Africa: 1976-2006

Enteropathogenic viruses associated with acute gastroenteritis among African children under 5 years of age: A systematic review and meta-analysis

Gastroenteritis viruses are the leading etiologic agents of diarrhea in children worldwide. We present data from thirty-three (33) eligible studies published between 2003 and 2023 from African countries bearing the brunt of the virus-associated diarrheal mortality. Random effects meta-analysis with proportion, subgroups, and meta-regression analyses were employed. Overall, rotavirus with estimated pooled prevalence of 31.0 % (95 % CI 24.0-39.0) predominated in all primary care visits and hospitalizations, followed by norovirus, adenovirus, sapovirus, astrovirus, and aichivirus with pooled prevalence estimated at 15.0 % (95 % CI 12.0-20.0), 10 % (95 % CI 6-15), 4.0 % (95 % CI 2.0-6.0), 4 % (95 % CI 3-6), and 2.3 % (95 % CI 1-3), respectively. Predominant rotavirus genotype was G1P[8] (39 %), followed by G3P[8] (11.7 %), G9P[8] (8.7 %), and G2P[4] (7.1 %); although, unusual genotypes were also observed, including G3P[6] (2.7 %), G8P[6] (1.7 %), G1P[6] (1.5 %), G10P[8] (0.9 %), G8P[4] (0.5 %), and G4P[8] (0.4 %). The genogroup II norovirus predominated over the genogroup I-associated infections (84.6 %, 613/725 vs 14.9 %, 108/725), with the GII.4 (79.3 %) being the most prevalent circulating genotype. In conclusion, this review showed that rotavirus remains the leading driver of viral diarrhea requiring health care visits and hospitalization among under-five years children in Africa. Thus, improved rotavirus vaccination in the region and surveillance to determine the residual burden of rotavirus and the evolving trend of other enteric viruses are needed for effective control and management of cases.

Epidemiology of group A rotavirus in children under five years of age with gastroenteritis in N'Djamena, Chad

BACKGROUND

Group A Rotaviruses (RVA) is one of the most common causes of severe diarrhoea in infants and children under 5 years of age. Unlike many countries in the world where RVA surveillance/control is active, in Chad , there is currently no applied RVA immunization program and surveillance strategy. The present study aims to determine the prevalence and associated risk factors of RVA gastroenteritis among children under five years of age in N'Djamena.

METHOD

This study comprised two parts: (1) A cross-sectional study carried in four hospitals in N'Djamena between August and November 2019, to determine infection risk factors and evidence of RVA infection among children aged five and below, consulted or hospitalized for diarrhea. An ELISA based RVA VP6 protein detection was used to determine RVA infection prevalence. Infection results and sociodemographic data were statistically analysed to determine RVA infection risk factors. (2) A retrospective study that consisted of analysing the records of stool examinations of the period from January 2016 to December 2018, to determine the prevalence of infectious gastroenteritis among the target population.

RESULTS

For the cross-sectional study, RVA infection prevalence was 12.76% (18/141) with males (61.11%) being more affected (sex ratio: 1.57). Children below 12 months were the most affected age group (44.44%) and 44.4% were malnourished. The mean Vesikari score shows that 38.8% of children have a high severity level and 41.1% have a moderate level. For the retrospective study, 2,592 cases of gastroenteritis hospitalization were analysed; 980 out of 2,592 cases (37.81%) of hospitalization due to diarrhoea were due to diarrhoeagenic pathogens including Emtamoeba hystolitica, Gardia lamblia, Trichomonas hominis, Hymenolepis nana, Escherichia coli, Shigella spp, Proteus mirabilis, and Klebsiella oxytoca. Cases of diarrhoea with negative pathogen search were 1,612 cases (62.19%). The diarrhoea peak was observed during the dry seasons, and the age group under 11 months was the most affected was (57.3%).

CONCLUSION

This study describes the evidence of RVA infection among diarrhoeic children below five years of age in N'Djamena, thus indicates a serious health burden. Malnourishment younger age was the higher risk factor. Further studies are needed to determine the circulating strains prior to considering introduction of RVA vaccine and setup a routine rotavirus surveillance in Chad.

Circulating rotavirus P[8]-lineage IV, unlike P[8]-lineage III, significantly related to nonsecretors status in Iranian children

Rotavirus (RV) P[8] strains are responsible for the most of the RV infections globally and are significantly associated with the secretor and Lewis positive status. Among the distinct P[8] lineages, different ligand affinities have been detected which can be linked to differences in secretor status associated histo-blood group antigens (HBGAs). Herein, we report the lineages of P[8] strains and their associated secretor and Lewis antigen phenotypes in Iranian children. The phylogenetic tree and sequence analyses showed that the most common detected RV P[8] strain belonged to P[8]-lineage III (92%) and were significantly associated with secretor and Lewis positive status. In contrast, 8% of P[8] strains clustered into the P[8]-lineage IV and were significantly associated with nonsecretor status, implying that lineage IV tends to infect nonsecretor individuals. Furthermore, protein modeling and amino acid analyses of the VP8* glycan binding site of Iranian P[8]-lineage IV strains indicated two residual substitutions (T184V and N216V/I) compared to the P[8]-lineage III strains that might have affected the glycan affinity among P[8]-lineages IV strains. The corresponding residual changes might permit their continued transmission in nonsecretor children in competition with other P[8]-lineages. Although nonsecretors show natural resistant to P[8] strains, but such residual changes might overcome this natural resistance which in turn might indirectly contribute to the decline in the vaccine efficacy in populations where HBGA polymorphism allows their circulation at high frequency.

Association of histo-blood group antigens and predisposition to gastrointestinal diseases

Infectious gastroenteritis is a common illness afflicting people worldwide. The two most common etiological agents of viral gastroenteritis, rotavirus and norovirus are known to recognize histo-blood group antigens (HBGAs) as attachment receptors. ABO, Lewis, and secretor HBGAs are distributed abundantly on mucosal epithelia, red blood cell membranes, and also secreted in biological fluids, such as saliva, intestinal content, milk, and blood. HBGAs are fucosylated glycans that have been implicated in the attachment of some enteric pathogens such as bacteria, parasites, and viruses. Single nucleotide polymorphisms in the genes encoding ABO (H), fucosyltransferase gene FUT2 (Secretor/Se), FUT3 (Lewis/Le) have been associated with changes in enzyme expression and HBGAs production. The highly polymorphic HBGAs among different populations and races influence genotype-specific susceptibility or resistance to enteric pathogens and its epidemiology, and vaccination seroconversion. Therefore, there is an urgent need to conduct population-based investigations to understand predisposition to enteric infections and gastrointestinal diseases. This review focuses on the relationship between HBGAs and predisposition to common human gastrointestinal illnesses caused by viral, bacterial, and parasitic agents.

Epidemiology and pre-vaccine burden of rotavirus diarrhea in Democratic Republic of Congo (DRC): Results of sentinel surveillance, 2009-2019

INTRODUCTION

Since August 2009, the Democratic Republic of Congo (DRC) has implemented sentinel site surveillance for rotavirus gastroenteritis. Limited hospital studies have been carried out, in DRC, describing the epidemiology of rotavirus diarrhea before rotavirus vaccine introduction in October 2019. This analysis describes the epidemiology of rotavirus gastroenteritis and characteristics of circulating viral strains from 2009 to 2019.

MATERIALS AND METHODS

We analyzed demographic and clinic data collected from children < 5 years old enrolled at three rotavirus sentinel surveillance sites in DRC during 2009-2019, prior to rotavirus vaccine introduction in 2019. Data have been described and presented as mean ± standard deviation for quantitative variables with normal distribution, or as median with an interquartile range [Q1-Q3] for quantitative variables with non-normal distribution, or as absolute value with percentage for qualitative variables.

RESULTS

Between August 2009 and December 2019, 4,928 children < 5 years old were admitted to sentinel surveillance sites for gastroenteritis in the DRC; the rotavirus positivity rate was 60 %. There was a slight male gender predominance (56 %), and the majority of children (79 %) were 0-11 months of age. Every year, the incidence was highest between May and September corresponding to the dry and cool season. Genotyping was performed for 50 % of confirmed rotavirus cases. The most common G genotypes were G1 (39 %) and G2 (24 %) and most common P genotypes were P[6] (49 %) and P[8] (37 %). The most common G-P genotype combinations were G1P[8] (22 %), G2P[6] (16 %) and G1P[6] (14 %). Genotype distribution varied by site, age group, and year.

CONCLUSION

From 2009 to 2019, rotavirus-associated gastroenteritis represented a significant burden among DRC children under 5 who were admitted to sentinel sites. G1P[8] was the most commonly identified genotype. Continued monitoring after the introduction of rotavirus vaccine will be essential to monitor any changes in epidemiology.

Epidemiology of Group A Rotavirus Diarrhea among Children Hospitalized for Acute Gastroenteritis in Ondo State, Nigeria

Globally, infective group A rotavirus (RVA) enteric infection in children culminates in acute diarrheal disease, severe dehydration, and mortality in children under the age of 5 years, particularly in sub-Saharan Africa. This research sought to determine the prevalence of RVA diarrhea among children aged below 5 years in Ondo state, as one of the necessary frameworks before instituting a vaccine campaign, and to expand knowledge on the epidemiology of RVA diarrhea in Nigeria.

In a cross-sectional descriptive study between October 2012 and September 2014, convenience sampling was adopted to obtain demographic information, clinical details, and stool samples from accented under five children who sought treatment for acute gastroenteritis at designated hospitals in Akure and Owo, Nigeria. A total of 390 stool samples were collected from children with acute diarrhea and tested for VP6 RVA antigen using enzyme immunoassay. Data generated were analyzed using descriptive statistics and chi-square at α 0.05.

From the 390 children hospitalized for diarrhea, 240 samples (240/390; 61.5%) were from males, while 150 samples (150/390; 38.5%) were from females, representing a male:female ratio of 1.6:1. RVAs were found in 24.2% (58/240) males and 28% (42/150) females, giving a male-female ratio of 1:1.2 and total prevalence of 25.6% (100/390). RVA infection was inversely proportional to the age as a rate of 11.8% was observed in children aged above 36 months and 31.8% (35/110) in children 7 to 12 months, while the highest rate (45.7%) was among children ≤ 6 months old. No significant difference was found (chi-square = 0.712) in the induction of diarrhea in children from Akure and Owo, neither was there any significant difference in the rates of infection between the boys and girls in Akure (chi-square = 0.576) nor in Owo (chi-square = 0.333). Seasonal association (chi-square = 5.802) in RVA infection was observed in the rainy season of year 2013/2014 period.

RVA diarrhea occurred year-round at a prevalence of 25.6%, predominantly in females. A seasonal fluctuation was observed in the rainy and dry seasons of the 2-year period. RVA diarrhea occurred predominantly in children aged below 18 months of age, and may thus help in determining the optimal period/schedule of any immunization program.

Prevalence, Pattern and Genetic Diversity of Rotaviruses among Children under 5 Years of Age with Acute Gastroenteritis in South Africa: A Systematic Review and Meta-Analysis

Rotavirus is the most significant cause of severe acute gastroenteritis among children under 5 years of age, worldwide. Sub-Saharan Africa particularly bears the brunt of the diarrheal deaths. A meta-analysis was conducted on 43 eligible studies published between 1982 and 2020 to estimate the pooled prevalence of rotavirus infection and changes in the main rotavirus strains circulating before and after vaccine introduction among under-five children in South Africa. The pooled national prevalence of rotavirus infection was estimated at 24% (95% CI: 21-27%) for the pre-vaccination period and decreased to 23% (95% CI: 21-25%) in the post-vaccination period. However, an increased number of cases was observed in the KwaZulu-Natal (21-28%) and Western Cape (18-24%) regions post-vaccination. The most dominant genotype combinations in the pre-vaccine era was G1P[8], followed by G2P[4], G3P[8], and G1P[6]. After vaccine introduction, a greater genotype diversity was observed, with G9P[8] emerging as the predominant genotype combination, followed by G2P[4], G12P[8], and G1P[8]. The introduction of the rotavirus vaccine was associated with a reduction in the burden of rotavirus-associated diarrhea in South Africa, although not without regional fluctuation. The observed changing patterns of genotype distribution highlights the need for ongoing surveillance to monitor the disease trend and to identify any potential effects associated with the dynamics of genotype changes on vaccine pressure/failure.

Structural basis of P[II] rotavirus evolution and host ranges under selection of histo-blood group antigens

Group A rotaviruses cause severe gastroenteritis in infants and young children worldwide, with P[II] genogroup rotaviruses (RVs) responsible for >90% of global cases. RVs have diverse host ranges in different human and animal populations determined by host histo-blood group antigen (HBGA) receptor polymorphism, but details governing diversity, host ranges, and species barriers remain elusive. In this study, crystal structures of complexes of the major P[II] genogroup P[4] and P[8] genotype RV VP8* receptor-binding domains together with Lewis epitope-containing LNDFH I glycans in combination with VP8* receptor-glycan ligand affinity measurements based on NMR titration experiments revealed the structural basis for RV genotype-specific switching between ββ and βα HBGA receptor-binding sites that determine RV host ranges. The data support the hypothesis that P[II] RV evolution progressed from animals to humans under the selection of type 1 HBGAs guided by stepwise host synthesis of type 1 ABH and Lewis HBGAs. The results help explain disease burden, species barriers, epidemiology, and limited efficacy of current RV vaccines in developing countries. The structural data has the potential to impact the design of future vaccine strategies against RV gastroenteritis.

Prevalence of rotavirus A infection and the detection of type G3P[11] strain in ruminants in Yobe state, Nigeria

Rotaviruses have a worldwide distribution and the infection is associated with diarrhea in young of ruminants as well as children. However, limited data exist on its prevalence and types in Yobe state, Nigeria. Detection of rotavirus A and types in ruminant population in Yobe state was the aim of the study. A total of 470 diarrheic fecal samples were collected and tested for rotavirus and types using serology and molecular techniques respectively. A prevalence rate of 2.98% (14/470) was found in the three species with specific rates of 2.9% (6/202), 3.8% (6/158), and 1.8% (2/110) in goat, sheep, and cattle respectively. The prevalence rates of 3.6% (12/331), 1.2% (1/84), and 1.8% (1/55) were for those aged < 1-3, 4-6, and 7-9 months old, respectively, while 4.9% (9/185) and 1.7% (5/285) were in males and females respectively. Rotavirus genes VP7 and VP4 were detected in 2 (14.3%) out of the 14 ELISA-positive samples while deduced amino acid sequences of the major variable regions revealed the genes to belong to types G3P[11] strain. Significant association was found between the infection and sex (P < 0.05) unlike in the species and age groups of the ruminants. The circulation of rotavirus virus in ruminants and type G3P[11] in cattle has been confirmed in the study. Hence, there is a need for continuous surveillance, awareness campaign, and assessment of the economic losses and public health implications of rotavirus infection in Nigeria.

Molecular basis of P[II] major human rotavirus VP8* domain recognition of histo-blood group antigens

Initial cell attachment of rotavirus (RV) to specific cell surface glycan receptors, which is the essential first step in RV infection, is mediated by the VP8* domain of the spike protein VP4. Recently, human histo-blood group antigens (HBGAs) have been identified as receptors or attachment factors for human RV strains. RV strains in the P[4] and P[8] genotypes of the P[II] genogroup share common recognition of the Lewis b (Le^b) and H type 1 antigens, however, the molecular basis of receptor recognition by the major human P[8] RVs remains unknown due to lack of experimental structural information. Here, we used nuclear magnetic resonance (NMR) spectroscopy-based titration experiments and NMR-derived high ambiguity driven docking (HADDOCK) methods to elucidate the molecular basis for P[8] VP8* recognition of the Le^b (LNDFH I) and type 1 HBGAs. We also used X-ray crystallography to determine the molecular details underlying P[6] recognition of H type 1 HBGAs. Unlike P[6]/P[19] VP8*s that recognize H type 1 HBGAs in a binding surface composed of an α-helix and a β-sheet, referred as the “βα binding site”, the P[8] and P[4] VP8*s bind Le^b HBGAs in a previously undescribed pocket formed by the edges of two β-sheets, referred to as the “ββ binding site”. Importantly, the P[8] and P[4] VP8*s retain binding capability to non-Le^b type 1 HBGAs using the βα binding site. The presence of two distinct binding sites for Le^b and non-Le^b HBGA glycans in the P[8] and P[4] VP8* domains suggests host-pathogen co-evolution under structural and functional adaptation of RV pathogens to host glycan polymorphisms. Assessment and understanding of the precise impact of this co-evolutionary process in determining RV host ranges and cross-species RV transmission should facilitate improved RV vaccine development and prediction of future RV strain emergence and epidemics.

Rotaviruses (RV)s are the main cause of severe diarrhea in humans and animals. Significant advances in understanding RV diversity, evolution and epidemiology have been made after discovering that RVs recognize histo-blood group antigens (HBGAs) as host cell receptors or attachment factors. While different RV strains are known to have distinct binding preferences for HBGA receptor ligands, their molecular basis in controlling strain-specific host ranges remains unclear. In this study, we used solution nuclear magnetic resonance spectroscopy and X-ray crystallography to determine the molecular-level details for interactions of the human P[8] and P[6] RV VP8* domains with their HBGA receptors ligands. The distinct binding patterns observed between these major human RVs and their respective glycan ligands provide insight into the evolutionary relationships between different P[II] genotypes that ultimately determine host ranges, disease burden, zoonosis and epidemiology, which may impact future strategies for development of vaccines to protect against RV infections.

Histo-Blood Group Antigens in Children with Symptomatic Rotavirus Infection

Group A rotaviruses are a major cause of acute gastroenteritis in children. The diversity and unequal geographical prevalence of rotavirus genotypes have been linked to histo-blood group antigens (HBGAs) in different human populations. In order to evaluate the role of HBGAs in rotavirus infections in our population, secretor status (FUT2+), ABO blood group, and Lewis antigens were determined in children attended for rotavirus gastroenteritis in Valencia, Spain. During three consecutive years (2013-2015), stool and saliva samples were collected from 133 children with rotavirus infection. Infecting viral genotypes and HBGAs were determined in patients and compared to a control group and data from blood donors. Rotavirus G9P[8] was the most prevalent strain (49.6%), followed by G1P[8] (20.3%) and G12P[8] (14.3%). Rotavirus infected predominantly secretor (99%) and Lewis b positive (91.7%) children. Children with blood group A and AB were significantly more prone to rotavirus gastroenteritis than those with blood group O. Our results confirm that a HBGA genetic background is linked to rotavirus P[8] susceptibility. Rotavirus P[8] symptomatic infection is manifestly more frequent in secretor-positive (FUT2+) than in non-secretor individuals, although no differences between rotavirus G genotypes were found.

Molecular Epidemiology of Rotavirus in Children under Five in Africa (2006-2016): A Systematic Review

Group A human rotaviruses (RVA) are the most common causes of severe viral gastroenteritis in infants and young children worldwide. The available vaccines, while effective in Europe and North America have shown a reduced efficacy in Africa. One issue raised is the genetic variability of RVA. The objective of this study was to perform a literature review of molecular epidemiology to determine the prevalence of RVA genotypes circulating in Africa so as to establish a mapping of reliable data on these various genotypes. The search for articles was done from the National Institutes of Health (PUBMED) using three set of keywords. Articles were selected with inclusion criteria such as the date of publication, the age of the children, the sample size and the diagnostic techniques (standardized laboratory techniques). The data were imported into STATA SE version 11 software. Specific prevalence was estimated with Confidence Intervals (CI) of 95%. A total of 326 published studies were initially retrieved, out of which 27 studies were finally selected for the systematic review. The selected studies cover 20 African countries. The most encountered genotypes in Africa during this period were G1 (32.72%), followed by G2 (17.17%), G3 (9.88%), G9 (8.61%) and G12 (7.56%) among the G-types. The most common P-types were P[8] (48.71%) followed by P[6] (22.60%) and P[4] (11.58%) and the G1P[8] combination (22.64%) was the most encountered followed by G2P[4] (8.29%), G9P[8] (6.95%) and G2P[6] (5.00%). North Africa presented the highest prevalence of the P[8] genotype (65.70%). This review provides a comprehensive view of the current circulating rotavirus strains in Africa, which can be important in light of the new rotavirus vaccinations. Indeed, in Africa, the pursuit of national and continental studies for epidemiological surveillance of circulating rotavirus strains is vital for the promotion of future successful vaccines.

Diarrhoea in children under five years of age in South Africa (1997-2014)

OBJECTIVE

To present evidence from available reliable published data on the prevalence, incidence and severity of diarrhoea in children aged under five years in South Africa.

METHODS

We searched seven electronic databases. Two reviewers assessed the studies independently and extracted outcome data. The heterogeneity of the studies did not allow for a meta-analysis.

RESULTS

We found only one nationally representative study conducted in 1998 reporting a diarrhoea prevalence of 13% in children under five. Other studies were conducted in smaller settings across the country. Diarrhoea incidence was 10.13 per 1000 person years in children admitted to a tertiary hospital. Three studies reported severity of diarrhoea; however, they differed across study settings and time period.

CONCLUSION

The paucity of nationally representative prevalence data for SA necessitates more national surveys with standardised data-collection methods to allow for more effective comparisons.

Epidemiology of rotavirus A diarrhea in Chókwè, Southern Mozambique, from February to September, 2011

Acute diarrhea disease caused by Rotaviruses A (RVA) is still the leading cause of morbidity and mortality in children ≤5 years old in developing countries. An exploratory cross-sectional study was conducted between February and September, 2011 to determine the proportion of acute diarrhea caused by RVA. A total of 254 stool specimens were collected from children ≤5 years old with acute diarrhea, including outpatients (222 children) and inpatients (32 children), in three local health centers in Chókwè District, Gaza Province, South of Mozambique. RVA antigens were detected using enzyme immunoassay (EIA); the RVA G (VP7) and P (VP4) genotypes were determined by RT-PCR or analysis sequencing. Sixty (24%) out of 254 fecal specimens were positive for RVA by EIA; being 58 (97%) from children ≤2 years of age. RVA prevalence peaks in June and July (coldest and drier months) and the G[P] binary combination observed were G12P[8] (57%); G1P[8] (9%); G12P[6] (6%); and 2% for each of the following genotypes: G1P[6], G2P[6] G4P[6], and G9P[8]. Non-Typeable (NT) G and/or P genotypes were observed as follows: G12P [NT] (6%); G1P [NT], G3P[NT] and GNTP[NT] (4%). Considering the different GP combinations, G12 represented 67% of the genotypes. This is the first data showing the diversity of RVA genotypes in Mozambique highlighting the epidemiological importance of these viruses in acute diarrhea cases in children ≤2 years old. In addition, these findings will provide a baseline data before the introduction of the RVA monovalent (Rotarix(®) ) vaccine in the National Immunization Program in September 2015. J. Med. Virol. 88:1751-1758, 2016. © 2016 Wiley Periodicals, Inc.

Association of Maternal Immunity with Rotavirus Vaccine Immunogenicity in Zambian Infants

Introduction

Live attenuated oral vaccines against rotavirus (RV) have been shown to be less efficacious in children from developing countries. Reasons for this disparity are not fully understood. We assessed the role of maternal factors including breast milk RV-specific IgA, transplacentally acquired infant serum RV-specific IgG and maternal HIV status in seroconversion among Zambian infants routinely immunized with Rotarix™ (RV1).

Methods

420 mother-child pairs were recruited at infant age 6–12 weeks in Lusaka. Clinical information and samples were collected at baseline and at one month following the second dose of RV1. Determination of breast milk RV-specific IgA and serum RV-specific IgA and IgG was done using standardized ELISA. Seroconversion was defined as a ≥ 4 fold rise in serum IgA titre from baseline to one-month post RV1 dose 2, while seropositivity of IgA was defined as serum titre ≥ 40 and antibody variables were modelled on log-base 2. Logistic regression was used to identify predictors of the odds of seroconversion.

Results

Baseline infant seropositivity was 25.5% (91/357). The seroconversion frequency was 60.2% (130/216). Infants who were IgA seropositive at baseline were less likely to seroconvert compared to their seronegative counterparts (P = 0.04). There was no evidence of an association between maternal HIV status and seroconversion (P = 0.25). Higher titres of breast milk rotavirus-specific IgA were associated with a lower frequency of seroconverson (Nonparametric test for trend Z = -2.84; P<0.01): a two-fold increase in breast milk RV-specific IgA titres was associated with a 22% lower odds of seroconversion (OR = 0.80; 95% CI = 0.68–0.94; P = 0.01). There was seasonal variation in baseline breast milk rotavirus-specific IgA titres, with significantly higher GMTs during the cold dry months (P = 0.01).

Conclusion

Low immunogenicity of RV1 vaccine could be explained in part by exposure to high antibody titres in breast milk and early exposure to wild-type rotavirus infections. Potential interference of anti-RV specific IgA in breast milk and pre-vaccination serum RV specific-IgA and IgG titres with RV1 seroconversion and effectiveness requires further research.

Engineering and expression of a human rotavirus candidate vaccine in Nicotiana benthamiana

BACKGROUND

Human rotaviruses are the main cause of severe gastroenteritis in children and are responsible for over 500 000 deaths annually. There are two live rotavirus vaccines currently available, one based on human rotavirus serotype G1P[8], and the other a G1-G4 P[8] pentavalent vaccine. However, the recent emergence of the G9 and other novel rotavirus serotypes in Africa and Asia has prompted fears that current vaccines might not be fully effective against these new varieties.

RESULTS

We report an effort to develop an affordable candidate rotavirus vaccine against the new emerging G9P[6] (RVA/Human-wt/ZAF/GR10924/1999/G9P[6]) strain. The vaccine is based on virus-like particles which are both highly immunogenic and safe. The vaccine candidate was produced in Nicotiana benthamiana by transient expression, as plants allow rapid production of antigens at lower costs, without the risk of contamination by animal pathogens. Western blot analysis of plant extracts confirmed the successful expression of two rotavirus capsid proteins, VP2 and VP6. These proteins assembled into VLPs resembling native rotavirus particles when analysed by transmission electron microscopy (TEM). Expression of the rotavirus glycoprotein VP7 and the spike protein VP4 was also tried. However, VP7 expression caused plant wilting during the course of the time trial and expression could never be detected for either protein. We therefore created three fusion proteins adding the antigenic part of VP4 (VP8*) to VP6 in an attempt to produce more appropriately immunogenic particles. Fusion protein expression in tobacco plants was detected by western blot using anti-VP6 and anti-VP4 antibodies, but no regular particles were observed by TEM, even when co-expressed with VP2.

CONCLUSION

Our results suggest that the rotavirus proteins produced in N. benthamiana are candidates for a subunit vaccine specifically for the G9P[6] rotavirus strain. This could be more effective in developing countries, thereby possibly providing a higher overall efficacy for the existing vaccines. The production of rotavirus proteins in plants would probably result in lower manufacturing costs, making it more affordable for developing countries. Further investigation is required to evaluate the immunogenic potential of the VLPs and fusion proteins created in this study.

Rotavirus G and P types in children with acute diarrhea in Cairo, Egypt, 2011-2012

BACKGROUND

The WHO estimated the annual rotavirus-related mortality among children below 5 years old in Egypt in 2004 to be 30 deaths per 100 000, or out of an estimated 2616 deaths, 3.9% were because of rotavirus infection. The aim of this article was to study the epidemiology and circulating genotypes of rotaviruses in Cairo from 2011 to 2012.

MATERIALS AND METHODS

A total of 197 stool samples were collected from 130 inpatient children at the Cairo University Children Hospital and 67 outpatient children at the Al-Saff Children Clinic. The collected stool samples were then screened for rotavirus using enzyme immunoassay, followed by a screening for G-type and P-type using RT-PCR, and confirmation by sequence analysis.

RESULTS

Rotavirus was detected in 39.1% (77/197) of the children, with a higher rate in inpatients (43.9%, 57/130) than in outpatients (29.9%, 20/67). There was an increase of rotavirus infection in the winter season. The majority of rotavirus cases (85.7%) occurred during the first year of life. The predominant genotypes identified during this study were G3P[8] (37.7%) and G1P[8] (19.5%), but uncommon genotypes G1P[6] (3.9%), G9P[6] (1.3%), G8P[14] (1.3%), and G12P[6] (2.6%) were also detected.

CONCLUSION AND RECOMMENDATIONS

The change in genotype distribution, compared with previous studies, along with the high burden of rotavirus-associated diarrhea among Egyptian children below 2 years old, emphasizes the importance of continuing strain surveillance and the need of developing and introducing rotavirus vaccine in Egypt.

Zinc-fortified oral rehydration solution improved intestinal permeability and small intestinal mucosal recovery

A randomized double-blind placebo-controlled study was conducted in children admitted to hospital with gastroenteritis (≥3 loose stools per day). All were treated for 5 days following admission with either zinc (Zn, 3 mg) or without Zn-fortified rice-based oral rehydration solution (ORS). (13)C-sucrose breath test (SBT) and intestinal permeability (lactulose/rhamnose or L/R ratio) were performed concurrently prior to commencement of ORS with or without Zn and at day 5 post-admission. There was a significant improvement in the SBT results in both the Zn-fortified group, median (5th-95th percentile) 2.1% (0.4% to 8.3%) versus 4.4% (0.4% to 10.4%), P < .05, and control group, 1.4% (0.1% to 5.4%) versus 4.3% (0.4% to 11.4%), P < .05, between the day of admission and day 5 post-admission. In the Zn-fortified group, there was also a significant improvement in L/R ratio between the day of admission and day 5 post-admission, 53.0 (19.5-90.6) versus 17.7 (13.4-83.2), P < .05. Low levels of Zn improved intestinal permeability but did not enhance short-term recovery following diarrheal illness.

Enteric bacterial pathogens in children with diarrhea in Niger: diversity and antimicrobial resistance

Background

Although rotavirus is the leading cause of severe diarrhea among children in sub-Saharan Africa, better knowledge of circulating enteric pathogenic bacteria and their antimicrobial resistance is crucial for prevention and treatment strategies.

Methodology/Principal Findings

As a part of rotavirus gastroenteritis surveillance in Maradi, Niger, we performed stool culture on a sub-population of children under 5 with moderate-to-severe diarrhea between April 2010 and March 2012. Campylobacter, Shigella and Salmonella were sought with conventional culture and biochemical methods. Shigella and Salmonella were serotyped by slide agglutination. Enteropathogenic Escherichia coli (EPEC) were screened by slide agglutination with EPEC O-typing antisera and confirmed by detection of virulence genes. Antimicrobial susceptibility was determined by disk diffusion. We enrolled 4020 children, including 230 with bloody diarrhea. At least one pathogenic bacterium was found in 28.0% of children with watery diarrhea and 42.2% with bloody diarrhea. Mixed infections were found in 10.3% of children. EPEC, Salmonella and Campylobacter spp. were similarly frequent in children with watery diarrhea (11.1%, 9.2% and 11.4% respectively) and Shigella spp. were the most frequent among children with bloody diarrhea (22.1%). The most frequent Shigella serogroup was S. flexneri (69/122, 56.5%). The most frequent Salmonella serotypes were Typhimurimum (71/355, 20.0%), Enteritidis (56/355, 15.8%) and Corvallis (46/355, 13.0%). The majority of putative EPEC isolates was confirmed to be EPEC (90/111, 81.1%). More than half of all Enterobacteriaceae were resistant to amoxicillin and co-trimoxazole. Around 13% (46/360) Salmonella exhibited an extended-spectrum beta-lactamase phenotype.

Conclusions

This study provides updated information on enteric bacteria diversity and antibiotic resistance in the Sahel region, where such data are scarce. Whether they are or not the causative agent of diarrhea, bacterial infections and their antibiotic resistance profiles should be closely monitored in countries like Niger where childhood malnutrition pre-disposes to severe and invasive infections.

Norovirus and rotavirus survival in urine collected from a public ecological sanitation system in Ouagadougou, Burkina Faso

Urine from urine-diversion toilets (UDTs) is routinely used as fertilizer for urban agriculture in Ouagadougou, Burkina Faso. Because urine from UDTs can be accidentally spoiled by feces, we determined whether virulent enteric viruses could persist in urine that is used for agricultural purposes and pose a threat to human health. Urine samples (N = 60) were first collected from 42 UDTs during the months of January and February 2012 in Ouagadougou and screened negative for the presence of norovirus (NoV) and group A rotavirus (RV). Composite urine from five collection sites was used to determine whether spiked murine norovirus (MNV) and group A bovine rotavirus (boRVA) could remain infectious at 15, 25, and 42 °C over an incubation period of 42 days in phosphate buffered saline (control) and urine. For both viruses, infectivity was determined by plaque assay and the presence of viral genome was evaluated by real-time RT-PCR. A decrease in the infectious titer was observed in composite urines that were experimentally seeded with MNV and boRVA. The decrease in the infectious titer was greater for MNV than for boRVA. Given that MNV was more labile to urine than boRVA was, MNV and boRVA genomes were still detectable after the 42 and 49 days incubation period for MNV and boRVA, respectively. Our data using substitutes of human NoV and RV suggested that there is a virucidal activity of urine against RVs and NoVs, given that the effect was lesser for RV. In spite of disappointing results for boRVA, the use of urine as fertilizer is still promising provided that future safety studies are extended to other enteric viruses.

Detection and molecular characterisation of noroviruses in hospitalised children in Malawi, 1997-2007

Despite the increasing recognition of noroviruses as major pathogens associated with community-acquired diarrhoea in children, there are few studies from Africa. Long-term surveillance studies of rotavirus gastroenteritis in Malawian children have provided an opportunity to undertake a study of the importance and epidemiological features of norovirus infection in this population. Faecal specimens were collected from children <5 years of age admitted to hospital with acute diarrhoea, as well as from a comparison group of diarrhoea-free children, in Blantyre, Malawi between 1997 and 2007. Norovirus was detected using real-time PCR and strains genotyped by nucleotide sequence analysis. Norovirus was detected in 220/1,941 (11.3%) faecal specimens, comprising genogroup GI (1.8%), GII (9.4%) and mixed GI/GII (0.1%). The median age of children with norovirus was 6 months (range, 0-48 months). Norovirus was detected throughout the year, with peaks at the end of the rainy season (March) and towards the end of the dry season (August-November). Norovirus GII.4 was the most commonly detected genotype accounting for 70% of strains characterised, followed by GII.2 (6%), GII.6 (4%) and GII.12 (4%). Sub typing of GII.4 noroviruses demonstrated local circulation of strains prior to their subsequent detection in association with global epidemics of gastroenteritis. The prevalence of norovirus in children without diarrhoea was similar to the level in cases. This largest study to date of norovirus infection in African children indicates the potential role of paediatric surveillance in predicting the emergence of norovirus strains with global epidemic potential.

Community-acquired infectious diarrhoea in children under 5 years of age in Dakar, Senegal

BACKGROUND

In sub-Saharan Africa, infectious diarrhoea is a major cause of childhood morbidity and mortality. A cross-sectional study was undertaken to document the pathogens potentially involved in community-acquired childhood diarrhoea in Dakar, the capital of Senegal.

METHODS

Between September 2007 and March 2008, 176 children aged 1 month to 5 years were recruited consecutively from a primary health care institution in an urban area. Clinical data were recorded and stool samples were collected. Bacterial pathogens were identified using conventional methods and/or PCR assays. Rotaviruses and adenoviruses were detected by a rapid immunochromatographic test. Intestinal parasites were diagnosed by microscopy.

RESULTS

Rotavirus was the most common enteric pathogen, detected in 27% of patients, followed by Shigella (12%), diarrhoeagenic Escherichia coli (8%), enteric adenovirus (8%), Salmonella (4%), Campylobacter jejuni (3%) and Plesiomonas shigelloides (2%). Mixed bacterial/viral infections were detected in 6% of cases. Parasites, mostly protozoa, were detected in 14% of children. Using ipaH PCR, 30% of samples were positive for Shigella/entero-invasive E. coli. Detection of rotavirus was more frequently associated with younger age groups (<24 months), whereas bacterial diarrhoea was isolated more often in children over 1 year of age. Detection of bacterial pathogens was significantly associated with malnutrition. Antibiotics were prescribed for 77% of children who attended for consultation. No pathogen was found in 36% of them, whereas a virus was detected without any other associated bacterial or parasitic pathogen in 23% of patients.

CONCLUSION

In developing countries, there is a need to develop reliable, easy-to-use, inexpensive rapid diagnostic tests to guide the management of diarrhoea in infants and children and thereby prevent over-use of antimicrobial agents.

Financing vaccinations - the South African experience

South Africa provides a useful country case study for financing vaccinations. It has been an early adopter of new vaccinations and has financed these almost exclusively from domestic resources, largely through general taxation. National vaccination policy is determined by the Department of Health, based on advice from a national advisory group on immunisation. Standard health economic criteria of effectiveness, cost-effectiveness, affordability and burden of disease are used to assess whether new vaccinations should be introduced. Global guidelines and the advice of local and international experts are also helpful in making the determination to introduce new vaccines. In terms of recent decisions to introduce new vaccines against pneumococcal disease and rotavirus diarrhoea in children, the evidence has proved unequivocal. Universal rollout has been implemented even though this has led to a fivefold increase in national spending on vaccines. The total cost to government remains below 1-1.5% of public expenditures for health, which is viewed by the South African authorities as affordable and necessary given the number of lives saved and morbidity averted. To manage the rapid increase in domestic spending, efforts have been made to scale up coverage over several years, give greater attention to negotiating price reductions and, in some cases, obtain initial donations or frontloaded deliveries to facilitate earlier universal rollout. There has been strong support from a wide range of stakeholders for the early introduction of new generation vaccines.

Case-control study of the etiology of infant diarrheal disease in 14 districts in Madagascar

Background

Acute diarrhea is a major cause of childhood morbidity and mortality worldwide. Its microbiological causes and clinico-epidemiological aspects were examined during the rainy seasons from 2008 to 2009 in 14 districts in Madagascar.

Methods

Stool specimens of 2196 children with acute diarrhea and 496 healthy children were collected in a community setting. Intestinal parasites were diagnosed by microscopy and bacteria by culturing methods. Rota-, astro and adenoviruses were identified using commercially available ELISA kits and rotaviruses were confirmed using reverse transcriptase polymerase chain reaction (RT-PCR).

Results

Intestinal microorganisms were isolated from 54.6% of diarrheal patients and 45.9% of healthy subjects (p = <0.01). The most common pathogens in diarrheic patients were intestinal parasites (36.5%). Campylobacter spp. and Rotavirus were detected in 9.7% and 6.7% of diarrheic patients. The detection rates of Entamoeba histolytica, Trichomonas intestinalis and Giardia lamblia were much greater in diarrheal patients than in non diarrheal subjects (odds ratios of 5.1, 3.2, 1.7 respectively). The abundance of other enteropathogens among the non diarrheal group may indicate prolonged excretion or limited pathogenicity.

Conclusion

In developing countries, where the lack of laboratory capacities is great, cross sectional studies of enteropathogens and their spatial distribution, including diarrheal and non diarrheal subjects, are interesting tools in order to advise regional policies on treatment and diarrheic patient management.

Spike protein VP8* of human rotavirus recognizes histo-blood group antigens in a type-specific manner

Rotaviruses (RVs), an important cause of severe diarrhea in children, have been found to recognize sialic acid as receptors for host cell attachment. While a few animal RVs (of P[1], P[2], P[3], and P[7]) are sialidase sensitive, human RVs and the majority of animal RVs are sialidase insensitive. In this study, we demonstrated that the surface spike protein VP8* of the major P genotypes of human RVs interacts with the secretor histo-blood group antigens (HBGAs). Strains of the P[4] and P[8] genotypes shared reactivity with the common antigens of Lewis b (Le(b)) and H type 1, while strains of the P[6] genotype bound the H type 1 antigen only. The bindings between recombinant VP8* and human saliva, milk, or synthetic HBGA oligosaccharides were demonstrated, which was confirmed by blockade of the bindings by monoclonal antibodies (MAbs) specific to Le(b) and/or H type 1. In addition, specific binding activities were observed when triple-layered particles of a P[8] (Wa) RV were tested. Our results suggest that the spike protein VP8* of RVs is involved in the recognition of human HBGAs that may function as ligands or receptors for RV attachment to host cells.

Health care seeking behavior for diarrhea in children under 5 in rural Niger: results of a cross-sectional survey

BACKGROUND

Diarrhea remains the second leading cause of death in children under 5 years of age in sub-Saharan Africa. Health care seeking behavior for diarrhea varies by context and has important implications for developing appropriate care strategies and estimating burden of disease. The objective of this study was to determine the proportion of children under five with diarrhea who consulted at a health structure in order to identify the appropriate health care levels to set up surveillance of severe diarrheal diseases.

METHODS

A cluster survey was done on 35 clusters of 21 children under 5 years of age in each of four districts of the Maradi Region, Niger. Caretakers were asked about diarrhea of the child during the recall period and their health seeking behavior in case of diarrhea. A weighted cluster analysis was conducted to determine the prevalence of diarrhea, as well as the proportion of consultations and types of health structures consulted.

RESULTS

In total, the period prevalence of diarrhea and severe diarrhea between April 24th and May 21st 2009 were 36.8% (95% CI: 33.7 - 40.0) and 3.4% (95% CI: 2.2-4.6), respectively. Of those reporting an episode of diarrhea during the recall period, 70.4% (95% CI: 66.6-74.1) reported seeking care at a health structure. The main health structures visited were health centers, followed by health posts both for simple or severe diarrhea. Less than 10% of the children were brought to the hospital. The proportion of consultations was not associated with the level of education of the caretaker, but increased with the number of children in the household.

CONCLUSIONS

The proportion of consultations for diarrhea cases in children under 5 years old was higher than those reported in previous surveys in Niger and elsewhere. Free health care for under 5 years old might have participated in this improvement. In this type of decentralized health systems, the WHO recommended hospital-based surveillance of severe diarrheal diseases would capture only a fraction of severe diarrhea. Lower levels of health structures should be considered to obtain informative data to ensure appropriate care and burden estimates.