Enteropathogens isolated from children with gastro-enteritis at Ga-Rankuwa Hospital, South Africa

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.

Prevalence of rotavirus infection in children below two years presenting with diarrhea

BACKGROUND

Rotavirus is a common cause of diarrhea in children. There is a need for data on prevalence of rotavirus diarrhea especially in our setting. This study was carried out to determine the prevalence of rotavirus infection in children upto two years presenting with diarrhea and to ascertain factors associated with rotavirus infection in them.

METHODS

A cross sectional observational study was carried out to determine the prevalence of rotavirus infection amongst children less than 2 years presenting with diarrhea. The clinical profile of the children was analyzed along with detection of rotavirus antigen in stool.

RESULTS

A total of 250 children with diarrhea were included in the study. The Male: Female ratio was 0.97:1. We found 24% children presenting with diarrhea to be positive for rotavirus antigen. 78.3% of children with rotaviral diarrhea were in the age group of 6-15 months. There was a significant association between type of feeding and rotavirus diarrhea with reduced prevalence while on exclusive breast-feeding. Though only 10.4% of children with rotavirus diarrhea had severe dehydration, 61.5% of children with severe dehydration were positive for rotavirus.

CONCLUSION

Rotavirus diarrhea caused substantial morbidity in our study population. The rotavirus positivity in these children was 24% and there was a significant association of rotavirus infection with type of feeding and severity of dehydration.

Anticipating rotavirus vaccines: epidemiology and surveillance of rotavirus in South Africa

Rotavirus infection is associated with acute infantile gastroenteritis in infants and young children globally. In South Africa, rotavirus infection has been shown to be associated with approximately one-quarter of all diarrhoeal admissions to hospital. Rotavirus infection predominantly occurs in infants less than 12 months of age (75%) and has a peak of shedding during the cooler, drier months of the year. A secondary peak during the spring has been observed. Multiple infections with rotavirus and at least one other microbial agent are common. The circulating VP7 serotypes and VP4 genotypes have been determined in various regions of South Africa and show a geographic specific distribution. A decade previously, P[8]G1 or G4 strains predominated, and P[4]G2 strains occurred in an epidemic pattern in one region. More recently, rotavirus strains with P[6] genotype have become common and novel VP7/VP4 genotype combinations are occurring across the country. G9 strains have been reported from Cape Town to Vendaland. The circulating rotavirus types observed in this study add to the knowledge of the natural history of rotavirus infection and provide the groundwork to consider future vaccine strategies.

Seroepidemiological study of genogroup I and II calicivirus infections in South and southern Africa

Diarrhoea is associated with the daily death of between 180 and 200 children under the age of 5 years in South Africa. Until recently, many cases and outbreaks of diarrhoea were not associated with a known aetiologic agent. Previous studies using baculovirus-expressed Norwalk virus (NV) and Mexico virus (MxV) capsid antigens have shown that human calicivirus infection is common in South Africa. In this study, our surveillance was extended to different populations, as well as to four other southern African countries: Namibia, Angola, Zimbabwe, and Mozambique. More than 1,700 specimens, some involved in previous cohort studies of infectious diseases, were enrolled in the surveillance. The overall seroprevalence of antibody against NV was >90% for all cohorts except for Mozambican refugees that had 83. 8% sero-positivity. The MxV antibody prevalence was higher than NV, with >95% positivity for all cohorts, except for one in Namibia that had 81% exposure. This study is one of only a few reporting on the concurrent incidence of NV and MxV infections in a cohort study, and has determined that small round structured viruses are prevalent in the local populations of South and Southern Africa. These agents may account for a number of previously unknown or unidentified causes of diarrhoeal illness, in both adults and children, in southern Africa.

Managed care and public health departments: who is responsible for the health of the population?

This review examines changes over the past decade in the delivery of health care in the United States, specifically the move toward managed care and capitation. Over 77 million Americans are now enrolled in health maintenance organizations, and the health care delivery system is reorganizing into large group practices and integrated health systems. Examined here are the implications of this shift on the interaction between managed care and public health agencies. How will a population-based system of health care be achieved in light of managed care organizations' responsibility only for their enrolled population, in contrast to the responsibility of the public health service for the entire population? Where does the responsibility of MCOs end and that of public health begin? Should certain public health functions be absorbed by managed care organizations? What are the prospects for partnership between these two systems?

Epidemiological study on infectious diarrheal diseases in children in a coastal rural area of Kenya

Diarrheal diseases are major causes of morbidity and mortality among children in developing countries. We have analyzed the causative agents of diarrhea in children under five years of age who resided in rural environments but attended a hospital in Malindi, a coastal town in Kenya. Bacterial diarrhea was found in 239 (27.7%) of 862 patients with diarrhea. Diarrheagenic Escherichia coli, including enteropathogenic, enterotoxigenic, and enterohaemorrhagic strains, was isolated from 119 (13.8%) patients, followed by Salmonella spp. (63 cases, 7.3%) and Shigella spp. (56 cases, 6.5%). Intestinal parasites were found in 109 (12.6%) of the patients. Entamoeba histolytica and Giardia lamblia were found in 67 (7.8%) and 42 (4.9%) of the cases, respectively. Rotavirus was found in 69 (16.1%) of 428 cases, a part of the 862 cases. Significant differences in age distribution were seen in diarrheal cases due to Campylobacter spp., G. lamblia, and rotavirus. No significant seasonal incidence of specific pathogens was found, but the number of diarrheal patients was significantly correlated to rainfall. Drinking water was contaminated with bacteria at concentrations ranging from 10(3) to 10(6) CFU/ml in 98% of the households and by coliform bacteria at concentrations of 10(2) to 10(5) CFU/ml in 72% of the households. These results suggest that the main routes of infection may be contaminated drinking water and fecal-oral transmission of enteric pathogens. Consequently, we propose that the enhancement of hygienic practice through health education is a feasible control measure of diarrhea in the study area.

Study of Norwalk virus and Mexico virus infections at Ga-Rankuwa Hospital, Ga-Rankuwa, South Africa

Small round-structured viruses (SRSVs) or Norwalk-like viruses have been implicated as an important causative agent of gastroenteritis outbreaks. We used the relatively newly developed recombinant enzyme immunoassays (EIAs) to determine the seroprevalence of Norwalk virus (NV) and Mexico virus (MxV) in a family-based cohort and an antenatal clinic cohort at Ga-Rankuwa Hospital, Ga-Rankuwa, South Africa. High prevalences (96 to 99%) of anti-NV and anti-MxV antibodies were detected in both cohorts. We also investigated the pattern of antibody acquisition in a cohort of infants and young children without gastroenteritis and found that by 48 months of age all children had acquired adult antibody levels to both these viruses. Lastly, we tested 276 stool specimens collected from infants and young children with gastroenteritis for the presence of NV or MxV antigen by recombinant EIAs to each virus, by electron microscopy (EM), and by reverse transcription (RT)-PCR. NV and MxV antigens were present in 1.8 and 4.3% of the stool specimens, respectively, by the recombinant EIAs; 9.2% were positive for SRSVs by EM, and 25% of these SRSVs gave a positive result by RT-PCR for primer pair 35-36 directed to a region of the RNA-dependent RNA polymerase gene. The seroprevalence studies indicate a high level of exposure to these viruses in both children and adults. Although the viral antigens are not highly prevalent in diarrheal stools, it was determined by the two assays for NV and MxV that children are, nevertheless, infected early in life.

Campylobacter jejuni/coli and enterotoxigenic Escherichia coli (ETEC) in faeces from children and adults in Tanzania

The occurrence of Campylobacter and enterotoxigenic E. coli (ETEC) was studied in faecal samples from Tanzanian children (< 5 years of age), adolescents and adults (only Campylobacter) with and without diarrhoea. The Campylobacter strains isolated were tested for subspecies, enterotoxigenicity and serotype. Out of 394 children with diarrhoea 18% were infected with Campylobacter and 20% with ETEC. In 278 samples tested for Campylobacter and 136 tested for ETEC from asymptomatic children the corresponding numbers were 12 and 5%, respectively. In children < 18 months with diarrhoea Campylobacter was noted in 22% and ETEC in 18%, whereas the figures were 11 and 4% respectively in asymptomatic children. In the age group 18 months to 5 years Campylobacter was demonstrated in 2% of the children with diarrhoea and 27% had ETEC, while the figures were 15 and 8% for asymptomatic children. Among adults the prevalence of Campylobacter-positive samples was 1% both for symptomatic and asymptomatic individuals. There were no seasonal differences in the prevalences of both Campylobacter and ETEC either in the symptomatic or the asymptomatic group. Campylobacter jejuni was the dominating Campylobacter species among both symptomatic and asymptomatic individuals. C. jejuni strains from patients with diarrhoea were significantly more often enterotoxigenic than were C. coli strains. The serotype pattern regarding Campylobacter was in general similar for symptomatic and asymptomatic individuals. We conclude that Campylobacter and ETEC are common causes of bacterial diarrhoea in Tanzanian children, and that Campylobacter infections are more important in children younger than 18 months, than in older ones.

Adhesion and its role in the virulence of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) organisms are an important cause of diarrheal disease in young children. The virulence of EPEC is a multifactorial process and involves a number of distinct stages. Initial adherence to intestinal mucosa is mediated by fimbriae which bring about a distinct form of adhesion, localized adhesion. Intimate adhesion of the bacterium to the eukaryotic membrane occurs, resulting in the activation of signal transduction pathways. Microvilli are disrupted and effaced from the apical membrane which then cups around the organism to form pedestal structures, the attaching and effacing lesion. Diarrhea may be produced by alteration of the permeability of the apical membrane and also through a malabsorption mechanism. The pathways involved in the production of the attaching and effacing lesion are described. EPEC organisms were originally thought to belong to a number of distinct serogroups; it is now apparent that many isolates belonging to these serogroups are not pathogenic or belong to other pathogenic groups of E. coli. In addition, isolates falling outside of these serogroups are considered to be true EPEC. The definition of EPEC based on serotyping is inaccurate and should be replaced by methods that specifically detect the virulence properties of EPEC.

Early child health in Lahore, Pakistan: VIII. Microbiology

The causative agents of acute diarrhoea were investigated in children under the age of five years from 1985-1991 in three socio-economically different areas in Lahore, Pakistan. The aim was to determine the frequencies of the most common enteropathogens in faeces. The total isolation rate was 73.4%; two thirds (53.5%) were of bacterial and one third (19.9%) of viral origin. ETEC-LT (23.4%), Rota virus (19.9%), EPEC (15%) and Campylobacter (12%) were the single most frequent pathogens in all age groups and areas of living. The positivity of Campylobacter increased from 1.6% to 12% after the change of isolation technique. Shigella was isolated significantly (p > 0.001) more in children over than under one year of age. The incidence of bacterial infections was high during all seasons, while in certain years Rota virus was relatively low in the summer compared to the cooler months. The prevalence of ETEC-LT diarrhoea was higher in the periurban slum as compared to the village and the urban slum. The study is the first of its kind in Pakistan, and the results are similar to other comparable studies. It is thus possible to establish a well functioning and reliable microbiological laboratory in developing countries in a setting with restricted trained personnel and material resources.

The relative importance of Shigella in the aetiology of childhood gastroenteritis in Saudi Arabia

The role of shigella infection in childhood gastroenteritis was studied over a 2-year period. Shigella species were found in the faecal specimens of 70 (1%) of 7369 children with gastroenteritis, but in only 1 (0.1%) of 1130 controls. S. flexneri was the commonest isolate (51%), followed by S. sonnei (37%). Most shigella species were isolated during the winter. The prevalence of shigellosis was highest for children 1-5 years of age but equal for both sexes. Fever, abdominal cramps, vomiting, and bloody diarrhoea were the predominant clinical features. Of the shigella isolates, 73% were resistant to cotrimoxazole, 43% to ampicillin, and 41% to chloramphenicol. One-third of isolates were resistant to greater than or equal to 3 antibiotics. All isolates were susceptible to nalidixic acid. The illness was mild and self-limiting and most patients recovered without antimicrobial therapy.

Cryptosporidiosis

Before 1982, only eight case reports of human cryptosporidiosis and fewer than 30 papers on Cryptosporidium spp. appeared in the biomedical literature. At that time, cryptosporidiosis was thought to be an infrequent infection in animals and rarely an opportunistic infection in humans. The concept of Cryptosporidium spp. as pathogens has changed dramatically within the past 8 years because of improved diagnostic techniques, increased awareness within the biomedical community, and the development of basic research programs in numerous laboratories. Presently, greater than 1,000 publications including over 400 case reports in the biomedical literature address Cryptosporidium spp. and cryptosporidiosis. Cryptosporidium parvum is now thought to be one of the three most common enteropathogens causing diarrheal illness in humans worldwide, especially in developing countries. It is likely that cryptosporidiosis was previously included in the 25 to 35% of diarrheal illness with unknown etiology. Because of the severity and length of diarrheal illness and because no effective therapy has been identified, cryptosporidiosis is one of the most ominous infections associated with AIDS. The role of C. parvum as an enteropathogen is well established; documentation of its role as a cause of hepatobiliary and respiratory diseases is now appearing in the literature. Our present understanding of the natural history, epidemiology, biology, and immunology of Cryptosporidium spp. as well as the clinical features, pathogenicity, and treatment of cryptosporidiosis are reviewed here.