Seroepidemiology of human group C rotavirus in South Africa

Sera from three separate healthy population cohorts were used to determine the incidence of group C rotavirus infections in 1,356 South Africans. Using an enzyme-linked immunosorbent assay based on a recombinant group C rotavirus VP6 protein, the total percent positivity was found to be 34.4% (range, 33 to 38%), with almost half of the population infected after the age of 20 years.

Comparative studies of human rotavirus serotype G8 strains recovered in South Africa and the United Kingdom

Epidemiological studies on the VP7 serotype prevalence of human rotaviruses in South Africa and the United Kingdom identified several strains which could not be serotyped as G1-G4 by monoclonal antibodies. Further analysis of these strains with a G8-specific monoclonal antibody and with probes for human rotaviruses confirmed them as G8 rotaviruses. These G8 strains exhibited a high degree of sequence identity when compared with each other and with other rotavirus G8 strains. Five South African strains were further characterized as VP6 subgroup I, but with a long RNA electropherotype, which is similar to the G8 strains previously isolated in Finland. In the UK strains, one was VP6 subgroup II with a long RNA electropherotype (similar to the Italian G8 strain). The other two were subgroup I with a short RNA electropherotype. None of these strains exhibited the super-short RNA electropherotype described in the prototype G8 strains recovered from Indonesia (69M).

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.

Rotavirus strains bearing the VP4P[14] genotype recovered from South African children with diarrhoea

Human rotavirus VP4P[14] strains were previously recovered in South Africa [18]. The strains exhibited a long RNA pattern, VP6 subgroup II and VP7 serotype G1. Two of the VP8 genes were cloned and sequenced and demonstrated a high nucleotide homology with the prototype P[14] strains (PA169 and HAL1166).

Astrovirus infection in South Africa: a pilot study

Astroviruses have been shown to be important aetiological agents associated with gastroenteritis in children, as have rotaviruses and the enteric adenoviruses. However, no inclusive studies have been conducted in South Africa to allow a comparison of the relative roles of these different viral agents. In this study, stool specimens were obtained between 1991 and 1993 from 225 young children with acute gastro-enteritis. These were examined for the presence of astroviruses using a monoclonal antibody-based ELISA, and for rotaviruses and enteric adenoviruses using commercially available kits. A control group of 56 infants and young children without symptoms of diarrhoeal illness was included in the study. Astroviruses were detected in 7% of the stools compared with 20% infected with rotaviruses and only 3% infected with enteric adenoviruses. In the control group, one specimen each had astrovirus or adenovirus and two shed rotaviruses. The astrovirus prevalence observed in this study is similar to that reported in other developing communities. Rotavirus and astrovirus infections were more prevalent in the autumn and early winter than in other seasons. Astrovirus and rotavirus infections predominated in children between 3 and 22 months of age.

Characterisation of gastro-enteritis-associated adenoviruses in South Africa

OBJECTIVE

To analyse adenovirus (Ad) numbers and types associated with paediatric gastro-enteritis in South Africa.

SETTING

Gauteng, 1994-1996.

METHODS

A total of 234 paediatric diarrhoeal stool samples were screened for Ad using commercial enzyme-linked immunosorbent assays (ELISAs). Adenoviral isolates were typed, where possible, using restriction enzyme analysis.

RESULTS

Ad was detected in 23 (9.8%) specimens, of which 8 (34.8%) were found by subgroup F-specific ELISA to contain Ad40 or 41. Six of these isolates were typed and 2 could not be typed. Of the remaining 15 specimens, 2 isolates had restriction profiles that did not correspond with known Ads, while 2 were identified as Ad31 and 1 as a subgroup C Ad. The remaining 10 specimens negative for Ad40/41 were non-cultivable and could not be typed.

CONCLUSIONS

The high percentage of non-cultivable Ads other than Ad40/41 is unusual, and may possibly indicate the prevalence of hexon variants of Ad40/41 or of emerging Ad types in South Africa.

Human Group C rotaviruses identified in Nigerian children

A survey investigating the prevalence of rotavirus infection in infants and young children with acute diarrhoea was undertaken in Jos State, Nigeria during the first half of 1998. In total, 182 faecal specimens were collected from children aged between 1 and 60 months with acute infantile gastroenteritis. Examination with a commercial ELISA assay for the presence of group A rotavirus antigen revealed 16 specimens positive for this antigen. However, examination of the double stranded RNA of the viral genome by polyacrylamide gel electrophoresis showed the presence of three human group C rotaviruses. This is the first report of group C rotaviruses in Nigeria and West Africa.

Characterization of VP6 subgroup, VP7 and VP4 genotype of rotavirus strains in Lusaka, Zambia

In a previous study, rotavirus infection was determined in young children at the University Teaching Hospital in Lusaka. In this study, selected rotavirus strains were characterized by monoclonal antibody assay to the VP6 subgroup antigen present and by hybridization analysis of the VP7 and VP4 genes carried by the virus. The majority of the strains were characterized as a VP6 subgroup II, VP7 serotype G1 strain with a long electropherotype and bearing the VP4 P8 genotype. A further four minor rotavirus strains with a long RNA electropherotype and subgroup II antigen were also observed to be circulating bearing G1 or G4 VP7 genes and the VP4 P8 genotype. Two electrophoretic strains with differing short RNA electropherotypes and subgroup I antigenicity were also present. These strains hybridized to the VP7 type G2 and VP4 P4 genotype probes.

Epidemiology of rotavirus diarrhoea in Africa: a review to assess the need for rotavirus immunization

Rapid progress towards the development of rotavirus vaccines has prompted a reassessment of the disease burden of rotavirus diarrhoea in developing countries and the possible impact of these vaccines in reducing diarrhoeal morbidity and mortality among infants and young children. We examined the epidemiology and disease burden of rotavirus diarrhoea among hospitalized and clinic patients in African countries through a review of 43 published studies of the etiology of diarrhoea. The studies were carried out from 1975 through 1992, and only those in which a sample of more than 100 patients with diarrhoea were specifically screened for rotavirus by using an established diagnostic test were included. Rotavirus was detected in a median of 24% of children hospitalized for diarrhoea and in 23% who were treated as outpatients; 38% of the hospitalized patients with rotavirus were < 6 months and 81% were < 1 year of age. Rotavirus was detected year-round in nearly every country and generally exhibited distinct seasonal peaks during the dry months. In 5 countries where rotavirus strains had been G-typed, 74% of strains were of one of the four common serotypes (G1 to G4), G1 was the predominant serotype, and 26% were non-typeable. This cumulative experience from 15 African countries suggests that rotavirus is the most important cause of severe diarrhoea in African children and that most strains in circulation today belong to common G types that are included in reassortant vaccines. Wherever large numbers of cases of rotavirus diarrhoea occur early in infancy, immunization at birth may protect the children before their first symptomatic infection.

Retreatment for significant regression after excimer laser photorefractive keratectomy. A prospective, randomized, masked trial

PURPOSE

Regression, a gradual partial or complete return to the myopic state, remains a common complication of excimer laser photorefractive keratectomy (PRK) and limits the predictability of refractive outcome, especially in high myopia. An estimated 10% to 20% of patients, therefore, request a repeat PRK procedure. This study was designed to provide patient selection criteria and guidelines for successful retreatment.

METHODS

One hundred six patients who had regressed were randomized to 1 of 4 retreatment groups comprising (1) those with minimal haze after their first PRK who received an exact retreatment; (2) those with minimal haze treated with a 50% deliberate overcorrection; (3) those with significant haze (> or = 2+ haze) given an exact retreatment; and (4) those with significant haze who received a 50% overcorrection. A Visx 20/20 laser was used in each case. Mean follow-up after retreatment was 12 months (range, 6-18 months).

RESULTS

Deliberate overcorrection (groups 2 and 4) resulted in a statistically significantly better refractive outcome (P = 0.026 at 6 months). Analysis of variance showed that significant haze after the first PRK was the most important predictor of a poor outcome after retreatment, other factors being high original myopia, marked regression, and loss of best-corrected visual acuity.

CONCLUSIONS

A retreatment PRK procedure for significant regression will reduce residual myopia significantly in the majority of patients, and a deliberate overcorrection (50%) reduces the chance of further regression. However, patients with high myopia who have regressed beyond approximately -3.50 diopters originally and who show significant anterior stromal haze (> 2+) should be retreated only with great caution, because of the risk of further regression, haze, and loss of visual acuity.

Comparison of electron microscopy, enzyme-linked immunosorbent assay and latex agglutination for the detection of bovine rotavirus in faeces

The performance characteristics of 2 enzyme immunoassays (ELISAs) and 4 latex agglutination assays (LXs) were evaluated for the detection of bovine rotavirus in faecal specimens of young calves with diarrhoea. A total of 26 specimens from calves less than 5 months of age were examined with different commercial assays and compared with electron microscopy (EM) as the gold standard and with polyacrylamide gel electrophoresis (PAGE) for the detection of atypical, non-group A rotaviruses. In the 2nd study, EIA (Dako) and LX (Murex), the assays of choice, were used to analyse 97 further faecal specimens from calves with diarrhoea. The ELISAs proved to be the most sensitive compared with the other tests used. The EM and PAGE are 100% specific although slightly less sensitive than the commercial assays. The results show that all the commercial assays can accurately detect rotavirus in the stools of calves with gastroenteritis, although the suitability and choice of assay will depend upon the requirements of individual laboratories.

Snow mountain-like virus identified in young children with winter vomiting disease in South Africa

Human caliciviruses have been reported to be associated with both epidemics of acute diarrhoeal illness and with sporadic cases of gastroenteritis in children. In this study, we report the identification of genogroup II small round-structured viruses or human caliciviruses associated with an outbreak of winter vomiting disease in South Africa. The virus was initially identified by electron microscopic examination of the stools and then further characterised by recombinant immunoassay with expressed capsid proteins to human caliciviruses from genogroups I and II. Both antigenically by the EIA and by sequence analysis of a region of the RNA-dependent RNA polymerase gene, the virus was shown to belong to genogroup II of the human Caliciviridae.

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.

Characterisation of rotaviruses recovered from neonates with symptomatic infection

An unusually high number of diarrhoeal stools were obtained from neonates at different maternity units in Pretoria during late 1986 and the winter of 1987 and tested for the presence of rotavirus infection. Latex agglutination assay revealed rotavirus in 67% (93/139) of the stools from newborn babies. Gel electrophoresis of the rotavirus genome showed that a genomically stable strain of rotavirus was associated with the diarrhoeal illness in all maternity units investigated. Determination of the VP6 subgroup specificity using monoclonal antibodies demonstrated that all strains were of subgroup II. Examination of the VP4 and VP7 rotavirus genes, which encode for the outer capsid neutralisation proteins of the virus, was conducted by hybridisation analysis using probes directed at the divergent regions of the two genes. These results showed the presence of a VP7 serotype G4 rotavirus strain with a P6 VP4 genotype-the putative 'attenuated' VP4 gene allele-circulating in all maternity units studied.

Group B and C porcine rotaviruses identified for the first time in South Africa

The incidence of rotavirus at a pig farm in Gauteng was determined by polyacrylamide gel electrophoresis (PAGE). Faecal specimens were collected from 172 litters over a 6-month period. Rotavirus was detected in 37.8% of piglets exhibiting signs of scouring. When these PAGE patterns were examined, 84.6% group A, 4.6% group B and 10.8% group C rotaviruses were observed. A few specimens subsequently collected from other farms in the Gauteng. North-West and Northern Provinces also contained group B and C electropherotypes. This is the first report of group B and group C rotaviruses in the South African pig population.

Relative frequency of human rotavirus VP4 (P) genotypes recovered over a ten-year period from South African children with diarrhea

The relative frequency and distribution of the VP4 (P) genotypes of 227 human rotavirus field strains were investigated in South Africa. The stool samples were collected between 1984-1993 from infants and young children with diarrhea at Ga-Rankuwa Hospital, Pretoria, South Africa. The RNA was extracted from stools, heat denatured, and dot blotted onto nylon membranes. The blots were hybridized to PCR-generated, 32P radio-labelled VP4-specific probes (corresponding to the hyperdivergent region of the VP4 gene) of the following human rotavirus VP4 genotypes: P4, P6, P8, P9, P10, and P12. Of the 157 rotavirus strains typed by the probes, the P8 genotype was identified most frequently in 63.7% (n = 100) of the samples. The P4 and P6 genotypes were detected less frequently in 22.3% (n = 35) and 8.3% (n = 13) of the samples, respectively. Five cases of dual infection between P8 and P4 genotypes occurred, indicating the potential for reassortment between members of different rotavirus genogroups. The P9 genotype could not be confirmed in 3 cases (1.9%), while the P10 genotype was not observed at all, indicating the scarcity or absence of these VP4 genotypes in this region. Interestingly, we identified the newly-described P12 VP4 genotype in 6 cases (3.8%), suggesting a wide geographical distribution. Furthermore, several samples with sufficient RNA by gel electrophoresis remained untyped by the probes used in this study, and may represent putative "new" human VP4 genotype(s).

Monitoring of rotavirus infection in a paediatric hospital by RNA electrophoresis

During the spring of 1987 and the autumn of 1988, stool specimens were collected from infants and young children in the paediatric unit at H. F. Verwoerd Hospital, Pretoria, and examined for the presence of rotaviruses to assess the potential for hospital-acquired infection in the paediatric wards. Stool samples were also collected from children admitted to the hospital for causes unrelated to gastro-enteritis to investigate the possible asymptomatic carriage of rotavirus in this population. Hospital-acquired rotavirus infection was determined in only 9% of cases. Very little asymptomatic carriage of the virus was identified. Electrophoretic analysis of the rotavirus strains showed that the majority of the infections (20 of 42) were associated with a particular strain with a long RNA profile, while 7 minor strains co-circulated (5 with a long electrophoretype and 2 with a short one). An apparent small outbreak of nosocomial infection with a single strain was observed to occur in one of the paediatric wards during the spring and early summer.

Topical anaesthesia for phacoemulsification surgery

Although phacoemulsification with only topical anaesthesia is possible, the level of any discomfort perceived by the patient is unknown. Topical anaesthesia eliminates any risk of inadvertent ocular or orbital injury. Twenty-four patients undergoing phacoemulsification under only topical anaesthesia (g. amethocaine 1%) were compared with 23 patients undergoing the same procedure with peribulbar anaesthesia (5 ml lignocaine 2%, 5 ml bupivacaine 0.5% and 75 units hyaluronidase). Perceived pain on administration of the anaesthesia, per-operatively and post-operatively was assessed by a nursing officer using a visual analogue scale (0-10). It was found that there was no difference in pain score between the two groups on induction of anaesthesia. Per-operatively and post-operatively scores were higher in the topical group than in the peribulbar group (p < 0.05, Mann-Whitney U-test), though most of these were within the range 0-3, ('no pain' to 'slight pain'). There was no difference in the amount of analgesia dispensed to the two groups on the ward post-operatively. In conclusion, topical anaesthesia provides adequate anaesthesia for phacoemulsification. Although a small increase in the level of discomfort was observed, the pain levels reported were small and may not be clinically significant when set against the reduced incidence of anaesthetic-related complications.

Geographic distribution of human rotavirus VP4 genotypes and VP7 serotypes in five South African regions

The rotavirus outer capsid proteins elicit the production of neutralizing antibodies and are known to play a role in inducing resistance to disease. In this study, cDNA probes directed at the six most common human rotavirus VP7 serotypes (G1 to G4, G8, and G9) and five human rotavirus VP4 genotypes (P4, P6, P8, P9, and P10) were utilized. Hybridization analysis of 572 human rotavirus strains collected from five regions in South Africa was performed to determine the distribution of the VP7 serotypes and VP4 genotypes in nature. VP7 serotype G1 was identified most frequently, occurring in 51% of the rotavirus strains tested. VP7 serotypes G2 and G4 occurred in similar numbers, although their distribution varied regionally. Few serotype G3 strains and no G8 or G9 strains were identified. The P8 VP4 genotype occurred most frequently overall (66%), and the P4 genotype was detected next most frequently. The P6 genotype was identified in 28 symptomatically infected neonates and in 8 symptomatic infants. Few P9 strains were identified. The potential for reassortment events was demonstrated by dual infections with different viruses.

Repair of Descemet's membrane detachment after intraocular surgery

We repaired three unselected cases of Descemet's membrane detachment. A visually successful outcome was achieved in one case, an anatomically successful outcome in another, and no improvement in the last. We believe that large detachments should be repaired early rather than waiting for possible spontaneous reattachment, and we advocate sulfur hexafluoride fluid-gas exchange as the procedure of choice.

Detection and quantitation of hepatitis B virus DNA: comparison of two commercial hybridization assays with polymerase chain reaction

Serum hepatitis B virus (HBV) DNA is now the most important and reliable marker for monitoring hepatitis B viral replication. Quantitative detection of HBV DNA in serum is based on commercial standardized molecular hybridization test systems. We compared two hybridization assays, the Digene Hybrid Capture assay (Digene Diagnostics, Beltsville, MD) and the Abbott HBV DNA assay (Abbott Laboratories, North Chicago, IL, USA) with the polymerase chain reaction (PCR) technique, for detection and quantitative measurement of serum HBV DNA. Forty-two patients with various HBV serological marker profiles were included in this study. The patients were divided into four groups according to their HBV DNA values after HBV DNA determination in the serum by the Abbott assay. For each patient HBV DNA was then determined by the Digene assay and by PCR. In the case of Digene and PCR there was a 97.6% correspondence in the outcome of the two methods, whereas in the Abbott assay and PCR there was only 69% correspondence. The McNemar test of symmetry showed no statistically significant difference between the Digene assay and PCR, whereas there was a significant difference (P < 0.01) in the Abbott assay and PCR. For low positive HBV DNA values between 1.5 and 20 pg ml-1 the Abbott assay yields inconclusive results. Differences observed between the two hybridization assays underline the need for standardization of HBV DNA quantitation.