Hepatitis A virus in surface water in South Africa: what are the risks?

The aim of this study was to assess the potential risk of infection constituted by HAV to persons using surface dam and river water for domestic and recreational purposes. It estimates the potential risk using a deterministic exponential risk assessment model with mean values and conservative assumptions. Hepatitis A virus was detected in 17.5% of river and 14.9% of dam water samples tested. The number of indicator organisms in these sources exceeded drinking and recreational water quality guidelines set by the United States Environmental Protection Agency (US EPA), indicating possible health risks to recreational water users. Based on the available data and taking all the assumptions into consideration, the probability of infection (Pinf) to the higher socio-economic population using the river water for recreational purposes was 1.1 x 10(-3) per day and 3.3 x 10(-1) per annum if 100 ml was ingested per day. For recreation in the dam water the Pinf value was 1.2 x 10(-4) per day and 4.2 x 10(-2) per annum. For the lower socio-economic population, risk values for drinking purposes (2 L day(-1)) were ten-fold greater. These surface waters therefore did not conform to the US EPA guidelines of 1 infection per 10,000 consumers per year for drinking water or eight gastrointestinal illnesses per 1,000 bathers per day in environmental waters used for recreational purposes. This is the first risk assessment study addressing the risk of infection by HAV in surface water to different socio-economic populations in South Africa.

Prevalence of vaccine-derived polioviruses in stools of immunodeficient children in South Africa.

AIMS: The aim of the study was to determine the prevalence of vaccine-derived polioviruses (VDPVs) in stool specimens of immunodeficient patients such as HIV-positive children (including those with an AIDS indicator condition, according to the Centres for Disease Control and Prevention classification) by applying various molecular techniques. METHODS AND RESULTS: A total of 164 stool samples from HIV-positive children and 23 stool samples from healthy immunocompetent children (the control group) were analysed during 2003 and 2004. By applying a reverse transcription polymerase chain reaction (RT-PCR) in combination with a nested PCR, a total of 54 enteroviruses were detected in the stool specimens of the immunodeficient children. The use of restriction enzymes and a Sabin specific RT-triplex PCR confirmed the presence of 13 polioviruses (PVs), such as seven Sabin PV type 1, four Sabin PV type 3 and two Sabin PV type 2 isolates. The 5'untranslated region and the VP1 capsid-encoding protein of the 13 PVs and the three PVs from the stools of the immunocompetent children were partially sequenced and their genetic relatedness was deduced from the constructed phylogenetic trees. The majority of the PVs isolated from the stools of the immunodeficient children (10 of 13 isolates) were classified as 'oral poliovirus vaccine (OPV)-like viruses', as these isolates had close sequence relationships (>99% in VP1 nucleotide sequences) to the original Sabin PV vaccine strains. Three PVs showed < or =99% VP1 sequence identity to the Sabin PV vaccine strains and were classified as 'suspected' immunodeficient VDPVs (iVDPVs). All of the OPV-like isolates and the 'suspected' iVDPVs carried mutations at specific positions in their partially sequenced regions, which have been associated with reversion of the attenuated Sabin PV vaccine strains to increased neurovirulence. CONCLUSIONS: Thus, this study adds further evidence to the observation that immunodeficient individuals may excrete OPV strains with potential neurovirulent phenotypes. SIGNIFICANCE AND IMPACT OF THE STUDY: Prolonged excretion of PVs by immunodeficient individuals is of major concern, because continued replication of PVs in the human gut could result in the reversion of these viruses to greater neurovirulence. When exposed to OPV, immunodeficient patients may become chronically infected, spreading potentially neurovirulent VDPVs for many months or years to close contacts and children who are no longer being vaccinated after termination of OPV vaccination in the near future.

Molecular epidemiology of group A rotaviruses in water sources and selected raw vegetables in southern Africa.

Group A rotaviruses (RVs) are the most important cause of acute viral gastroenteritis in infants and young children. In this study raw and treated drinking water supplies at plants in two geographic areas, as well as selected irrigation water and corresponding raw vegetables in three regions of southern Africa, were screened for the presence of RVs using molecular techniques. Group A RVs were detected in 11.8% of partially treated and 1.7% of finally treated drinking water samples and in 14% of irrigation water samples and 1.7% of corresponding raw vegetable samples. Type-specific reverse transcriptase-PCR and sequence analysis revealed the presence of multiple types (G1, G2, G8, and G9) in irrigation water and single types (G1 or G3) in raw and treated drinking water. Group A RVs detected in all samples consisted of mixed P types (P[4], P[6], P[8], and P[9]), with P[6] predominating. The detection of types G8, G9, and P[6] reflects the emergence of these types in clinical infections. The similarity of environmental types to those in patients with clinical RV infections confirms the value of wastewater screening as a tool for assessing RVs circulating in communities, with the benefit of detecting types that cause both clinical and subclinical infections. The results provide new information on RV types in water and related environments and identify the potential risk of waterborne transmission. In addition, the presence of RVs in drinking water underlines shortcomings in quality specifications. These data provide valuable information regarding the prevalence of RVs in environmental sources, with important implications for vaccine development.

Detection and risk assessment of adenoviruses in swimming pool water.

AIMS: The role of swimming pool water as a source of human adenovirus (HAd) infection has previously been demonstrated. In this study, the risk of infection of HAds detected in a survey of swimming pool water from two indoor and one outdoor swimming pools over a period of 1 year was assessed. METHODS AND RESULTS: The HAds were concentrated from 1 l grab samples of swimming pool water using a silicon dioxide-based method. The extracted HAd DNA was amplified by means of a nested PCR method. Adenoviruses were detected in four of 26 samples (15.4%) from the indoor swimming pool A, eight of 38 samples (21.1%) from the indoor swimming pool B and three of 28 samples (10.7%) from the outdoor swimming pool C. Application of these results in an exponential risk assessment model indicated a daily risk of infection of 2.61 x 10(-3) for swimming pool A, 3.69 x 10(-3) for swimming pool B and 1.92 x 10(-3) for swimming pool C assuming a daily consumption of 30 ml of swimming pool water. CONCLUSIONS: No acceptable (tolerable) risk of infection has yet been recommended for swimming pool water. However, the quality of swimming pool water is generally expected to be similar to that of drinking water. One infection per 10 000 consumers per year has been recommended for drinking water. The risk of HAd infections calculated for the swimming pool water under investigation exceeded this acceptable risk. SIGNIFICANCE AND IMPACT OF THE STUDY: The finding that swimming pool water which conforms to generally accepted specifications for treatment, disinfection and indicator organisms constituted a risk of HAd infection, has implications for the swimming pool industry. The formulation of acceptable (tolerable) risks of infection for swimming pool water may be essential. Specifications will, therefore, have to be formulated to ensure that swimming pool water conforms to the acceptable risk of infection.

Risk assessment of adenoviruses detected in treated drinking water and recreational water.

AIMS: Human adenoviruses (HAds) have previously been detected in sewage and polluted river and dam water, as well as treated drinking water. The 51 serotypes of HAds cause a wide range of infections with clinical manifestations associated with the gastrointestinal, respiratory and urinary tracts, and the eyes. Water may play a meaningful role in the transmission of many of these HAd serotypes, specifically the enteric HAds which are transmitted via the faecal-oral route. The presence of these viruses in water used for drinking and recreational purposes is considered to constitute a potential health risk. In this study, the risk of infection by the group of HAds previously detected over a period of 1 year in selected drinking water supplies, as well as river and dam water used for recreational purposes, was assessed. METHODS AND RESULTS: Adenoviruses were previously detected in nine of 204 (4.41%) samples of two drinking water supplies (A and B) treated and disinfected according to international specifications, in four of 51 (7.8%) samples of river water and nine of 51 (17.7%) samples of dam water. Application of these previously published results in an exponential risk assessment model indicated an annual risk of infection of 1.01 x 10(-1) and 1.7 x 10(-1) for drinking water supplies A and B, respectively, assuming a daily consumption of 2 l day(-1). The daily risk of infection constituted by HAds in the river water was calculated as 1.71 x 10(-4), and in the dam water as 3.12 x 10(-5), assuming a consumption of 30 ml of water per day. CONCLUSIONS: The risk of infection exceeded the tolerable risk of one infection per 10 000 consumers per year proposed for drinking water. However, the results for river and dam water used for recreational purposes were within the tolerable risk of one infection per 1000 bathers per day proposed for environmental waters used for recreational purposes. SIGNIFICANCE AND IMPACT OF THE STUDY: The study showed that the risk of HAd infection calculated for the drinking water supplies and the recreational water may overestimate the actual risk of infection, as conservative values were assumed for some of the variables. For a more accurate assessment of the potential risk of infection research should at least include a thorough investigation of the water consumption of individuals in South Africa, and the efficiency of recovery of the glass wool adsorption-elution method.

Prevalence, quantification and typing of adenoviruses detected in river and treated drinking water in South Africa.

AIMS: Human adenoviruses (HAds), of which there are 51 serotypes, are associated with gastrointestinal, respiratory, urinary tract and eye infections. The importance of water in the transmission of HAds and the potential health risks constituted by HAds in these environments are widely recognized. Adenoviruses have not previously been quantified in river and treated drinking water samples. In this study, HAds in river water and treated drinking water sources in South Africa were detected, quantified and typed. METHODS AND RESULTS: Adenoviruses were recovered from the water samples using a glass wool adsorption-elution method followed by polyethylene glycol/NaCl precipitation for secondary concentration. The sensitivity and specificity of two nested PCR methods were compared for detection of HAds in the water samples. Over a 1-year period (June 2002 to July 2003), HAds were detected in 5.32% (10/188) of the treated drinking water and 22.22% (10/45) of river water samples using the conventional nested PCR method. The HAds detected in the water samples were quantified using a real-time PCR method. The original treated drinking water and river water samples had an estimate of less than one copy per litre of HAd DNA present. The hexon-PCR products used for typing HAds were directly sequenced or cloned into plasmids before sequencing. In treated drinking water samples, species D HAds predominated. In addition, adenovirus serotypes 2, 40 and 41 were each detected in three different treated drinking water samples. Most (70%) of the HAds detected in river water samples analysed were enteric HAds (serotypes 40 and 41). One HAd serotype 2 and two species D HAds were detected in the river water. CONCLUSIONS: Adenoviruses detected in river and treated drinking water samples were successfully quantified and typed. The detection of HAds in drinking water supplies treated and disinfected by internationally recommended methods, and which conform to quality limits for indicator bacteria, warrants an investigation of the risk of infection constituted by these viruses. The risk of infection may have implications for the management of drinking water quality. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique as it is the first report on the quantification and typing of HAds in treated drinking water and river water. This baseline data is necessary for the meaningful assessment of the potential risk of infection constituted by these viruses.

Prevalence of vaccine-derived polioviruses in sewage and river water in South Africa.

Polioviruses (PVs) are not associated with waterborne transmission to the same extent as many other enteric viruses. However, they are typically transmitted by the faecal-oral route, which implies that the risk of infection by exposure to the viruses in water cannot be underestimated. The risk appears particularly high for rural communities, which use sewage-polluted river water for domestic purposes. Thus, the presence in the environment of highly evolved, neurovirulent vaccine-derived poliovirus (VDPV) strains in the absence of polio cases would have important implications for strategies to terminate immunisation with oral poliovirus vaccine (OPV) following global polio eradication. The aim of the current study was to determine the prevalence of VDPVs in selected sewage and river water samples collected from 2001 to 2003, and to construct phylogenetic trees of the partially sequenced 5'untranslated region (5'UTR) and the VP1 region of the genomes to deduce the genetic relatedness between the PV strains. Using the monolayer plaque assay, 703 plaques from sewage and 157 plaques from river water samples were analysed. Application of a RT-multiplex PCR revealed that 176 of these plaques were non-polio enteroviruses, and 49 were PV isolates. The Sabin-specific RT-triplex PCR revealed the presence of 29 Sabin PV type 1, 8 Sabin PV type 2 and 12 Sabin PV type 3 isolates. The 5'UTR and the VP1 region of 13 PV type 1, 7 PV type 3 and 6 PV type 2 isolates were partially sequenced. The majority of the OPV isolates (24 out of 26) displayed close sequence relationships (>99% VP1 sequence identity) to the parental Sabin PV vaccine strains and were classified as "OPV-like viruses". Two isolates (D1 08/28 and OF1 05/21) were found to be highly divergent and were classified as "suspected" VDPVs. Isolate OF1 05/21 (a "suspected" VDPV type 1) showed more than 0.9% divergence in VP1, whereas isolate D1 08/28 (a "suspected" VDPV type 2) showed 1.4% divergence in VP1 from the parental Sabin PV vaccine strains. As with most of the other OPV-like isolates, these "suspected" VDPVs were carrying mutations, which have previously been associated with reversion of the attenuated Sabin PV strains to increased neurovirulence. It was estimated that the total period of replication for the two "suspected" VDPVs was between 12 and 16 months. In conclusion, this study provided new and relevant information on the prevalence of "suspected" VDPVs in sewage and river water, and opened the way to assess the possible broader significance of the findings reported here.

Detection of enteroviruses in untreated and treated drinking water supplies in South Africa.

Enteric viruses have been detected in many drinking water supplies all over the world. A meaningful number of these supplies were treated and disinfected according to internationally acceptable methods. In addition, counts of bacterial indicators (coliform bacteria and heterotrophic plate count organisms) in these water supplies were within limits generally recommended for treated drinking water and these findings have been supported by epidemiological data on infections associated with drinking water. The shortcomings of conventional treatment methods and indicator organisms to confirm the absence of enteric viruses from drinking water, was generally ascribed to the exceptional resistance of these viruses. In this study, the prevalence of enteroviruses detected from July 2000 to June 2002 in sewage, river-, borehole-, spring- and dam water as well as drinking water supplies treated and disinfected according to international specifications for the production of safe drinking water was analysed. A glass wool adsorption-elution technique was used to recover viruses from 10--20 l of sewage as well as environmental water samples, in the case of drinking water from more than 100 l. Recovered enteroviruses were inoculated onto two cell culture types (BGM and PLC/PRF/5 cells) for amplification of viral RNA with nested-PCR being used to detect the amplified viral RNA. Results from the study demonstrated the presence of enteroviruses in 42.5% of sewage and in 18.7% of treated drinking water samples. Furthermore, enteroviruses were detected in 28.5% of river water, in 26.7% of dam/spring water and in 25.3% of borehole water samples. The high prevalence of coxsackie B viruses found in this study suggested, that a potential health risk and a burden of disease constituted by these viruses might be meaningful. These findings indicated that strategies, other than end-point analysis of treated and disinfected drinking water supplies, may be required to ensure the production of drinking water that does not exceed acceptable health risks. More reliable approaches to ensure acceptable safety of drinking water supplies may be based on control by multiple-barrier principles from catchment to tap using hazard assessment and critical control point (HACCP) principles.

Prevalence of human adenoviruses in raw and treated water.

Human adenoviruses (HAds), of which there are 51 antigenic types, are associated aetiologically with gastrointestinal, respiratory, urinary tract and eye infections. The clinical importance of HAds and the potential health risks constituted by HAds in water environments are widely recognised. This study was conducted to assess the use of an optimised integrated cell culture molecular-based technique to determine the prevalence of HAds in raw and treated drinking-water supplies in South Africa. Selected supplies were monitored weekly for the presence of adenoviruses over a one-year period (July 2001 to June 2002). Drinking-water supplies were derived from acceptable quality surface water sources using treatment processes that conformed to international standards for the production of safe drinking water. Adenoviruses were detected by amplification in cell cultures, followed by amplifying the extracted nucleic acids using molecular techniques (nested PCR). HAds were detected in 29.8% (59/198) of the treated drinking water, 16% (8/50) of dam water and 44% (22/50) of river-water samples tested. The results of this study confirmed the presence of HAds in some raw and treated drinking water supplies in South Africa.

Application of a molecular method for the detection of group A rotaviruses in raw and treated water.

Group A human rotaviruses (HRVs) are the most important aetiological agents of acute viral gastroenteritis in infants and young children in both developing and industrialised countries. Rotaviruses are resistant to many chemical disinfectants and reportedly survive well in treated tapwater and sewage. In this study a group A specific reverse transcriptase-polymerase chain reaction (RT-PCR) followed by a nested-PCR was applied for the detection of HRVs in raw and treated drinking-water samples drawn at a water reclamation plant. For a period of two years (July 2000 to June 2002), borehole, raw and treated drinking-water samples were collected weekly. Viruses were recovered from the water samples using a glass wool adsorption-elution technique followed by secondary concentration using precipitation with polyethylene glycol. In the first year of the study group A HRVs were detected in 11% sewage samples, 8% partially treated waters and 5% final treated drinking waters. The results of the second year of the study showed the presence of group A HRVs in 11% sewage and untreated surface water samples, 15% partially treated water and 6.5% final treated drinking waters. No HRVs were detected in the water samples from the boreholes. The presence of group A HRVs in treated drinking-water samples suggested that this water could be a potential source of infection to consumers. The data also implied that either the water treatment did not remove HRVs or the treated water was contaminated post-treatment.

Detection of enteroviruses in treated drinking water.

This study deals with the routine monitoring of drinking water for the presence of enteroviruses, over a period of 1 year. A rapid and simple method was employed for the simultaneous detection and typing of enteroviruses in large-volume water samples. This included an integrated cell culture/nested PCR approach, followed by restriction enzyme analysis. The two drinking water supplies studied were derived from acceptable quality surface water sources using treatment processes, which conform to international specifications for the production of safe drinking water. Enteroviruses (predominantly coxsackie B viruses) were detected in 11% and 16% of the drinking water samples from two treatment plants, respectively. This study confirms that acceptable water quality indicators do not necessarily reflect the virus content of drinking water.

Potentially pathogenic features of heterotrophic plate count bacteria isolated from treated and untreated drinking water.

Heterotrophic plate counts (HPCs) are commonly used to assess the general microbiological quality of drinking water. Drinking water quality specifications worldwide recommend HPC limits from 100 to 500 cfu ml(-1). A number of recent studies revealed evidence that these bacteria may not be as harmless as generally accepted. It appears that immuno-compromised individuals are particularly at risk. This would include the very young and very old patients with diseases such as AIDS and patients on therapy for purposes such as organ transplantation and cancer treatment. In this study, 339 bacterial colonies were isolated at random from selected treated and untreated drinking water in South Africa using routine heterotrophic plate count tests. In a first step to screen for potentially pathogenic properties, 188 (55.5%) of the isolates showed alpha- or beta-haemolysis on human- and horse-blood agar media. Subsequent analysis of the haemolytic isolates for enzymatic properties associated with pathogenicity revealed the presence of chondroitinase in 5.3% of the isolates, coagulase in 16.0%, DNase in 60.6%, elastase in 33.0%, fibrinolysin in 53.7%, gelatinase in 62.2%, hyaluronidase in 21.3%, lecithinase in 47.9%, lipase in 54.8% and proteinase in 64.4%. Fluorescein and pyocyanin were not produced by any of the isolates. Among the haemolytic isolates, 77.7% were resistant to oxacillin 1 microg, 59.6% to penicillin G 2 units, 47.3% to penicillin G 10 units, 54.3% to ampicillin 10 microg and 43.1% to ampicillin 25 microg. Cell culture studies revealed that 96% of haemolytic isolates were cytotoxic to HEp-2 cells, and 98.9% of the 181 cytotoxic isolates adhered to HEp-2 or Caco-2 cells. HEp-2 cells were invaded by 43.6%, and Caco-2 cells by 49.7%, of the 181 cytotoxic isolates. The invasion index on HEp-2 cells ranged from 1.9 x 10(-1) to 8.9 x 10(-6), whereas the invasion index on Caco-2 cells varied between 7.7 x 10(-2) and 8.3 x 10(-6). The most commonly isolated genera with these potentially pathogenic features were Aeromonas, Acinetobacter, Aureobacterium, Bacillus, Chryseobacterium, Corynebacterium, Klebsiella, Moraxella, Pseudomonas, Staphylococcus, Tsukamurella and Vibrio. The results obtained in this study support earlier findings on potentially pathogenic features of bacteria detected by routine HPCs on drinking water. These findings are in agreement with some epidemiological studies, which indicated an association between HPCs in drinking water and the incidence of gastroenteritis in consumers. However, the extent of the health risk concerned needs to be defined in more detail for meaningful revision of quality guidelines for HPCs in drinking water.

Molecular characterization of astroviruses by reverse transcriptase PCR and sequence analysis: comparison of clinical and environmental isolates from South Africa.

A comparative analysis was performed with 25 isolates of astroviruses (AstVs) detected in sewage sources and 22 concurrently identified clinical AstV isolates from the Tshwane (Pretoria) Metropolitan Area in South Africa. The samples and specimens were screened for AstVs by using an enzyme immunoassay and/or a reverse transcriptase PCR (RT-PCR) for the highly conserved untranslated region (3' end) of the genome. The RT-PCR results were confirmed by oligonucleotide probe dot blot hybridization. Viable viruses were propagated in cell cultures for amplification when a minimal specimen was available or indeterminate sequences were obtained. AstV strains were characterized by RT-PCR and partial sequence analysis of the capsid region. The presence of multiple human AstV (HAstV) types in a single sewage sample complicated identification of individual strains, and additional type-specific RT-PCR and sequence analyses of the capsid region were required for characterization. Amplification and characterization of one genotype from a sample, therefore, did not preclude the possibility that a sample harbored additional different genotypes. Genotype and sequence information obtained from AstVs in wastewater samples were compared to information obtained from AstV strains from human stools. HAstV type 1 (HAstV-1), as well as HAstV-3, -5, -6, and -8, were identified among the clinical isolates, and HAstV-1, -2, -3, -4, -5, -7, and -8 were identified among the environmental samples. Phylogenetic analysis demonstrated that HAstV-1, -3, -5, and -8, which were present in human stool and sewage samples, clustered together, indicating that these viruses are closely related. The concurrent presence of identical HAstV strains in wastewater samples and in hospitalized patients suggests that AstVs present in the environment pose a potential risk to communities in which fecally contaminated water is used for recreational and domestic purposes.

Distribution of genotypes of F-specific RNA bacteriophages in human and non-human sources of faecal pollution in South Africa and Spain.

AIMS: To assess whether the distribution of genotypes of F-specific RNA bacteriophages reflects faecal pollution of human and animal origin in water environments. METHODS AND RESULTS: Stool samples, animal feedlot waste slurries and a wide variety of faecally polluted waters were studied in South Africa and Spain. Genotyping was performed by plaque and spot hybridization with genotype-specific probes. Only genotypes II and III were detected in human stool. Animal faeces contained predominantly, but not exclusively, genotypes I and IV. Raw hospital and municipal sewage contained mostly genotypes II and III, whereas genotypes I and II prevailed in settled sewage, secondary treated sewage and non-point diffuse effluents from developing communities. Abattoir wastewaters contained mostly genotypes I and IV. No differences were observed between the distribution of genotypes in Spain and South Africa. CONCLUSIONS: Although the association of genotypes II and III with human excreta and I and IV with animal excreta was statistically significant, the results suggest that the association cannot be used for absolute distinction between faecal pollution of human and animal origin. SIGNIFICANCE AND IMPACT OF THE STUDY: This study contributes greatly to understanding the usefulness of genotypes of F-specific RNA bacteriophages in source tracking of faecal wastes.

The occurrence of E. coli O157:H7 in South African water sources intended for direct and indirect human consumption.

The occurrence of Escherichia coli O157:H7 in selected water samples in South Africa was investigated. The chromogenic Rainbow agar O157 medium designed for the rapid identification of E. coli O157:H7 was used for the detection of these organisms in various river-water samples in the Vaal Barrage Reservoir drainage basin of South Africa. A total of 204 samples were obtained from 15 sites where water was used for direct and indirect human consumption. Samples were filtered through Gelman filter-units and incubated on Rainbow agar O157 which produced different colours according to the bacterial chromogenic properties. Six hundred and sixty-three suspected E. coli O157:H7 colonies, with colours ranging between dark blue, grey and black, were subcultured onto sorbitol-MacConkey agar and screened for different virulence factors specific for E. coli O157:H7 and agglutination with anti-E. coli O157 antiserum. The results indicated that none of the suspected colonies contained all of the virulence factors necessary to classify them as E. coli O157:H7. None of these organisms agglutinated with antisera against E. coli O157. The probability of being infected with E. coli O157:H7 from direct or indirect consumption of these river water sources is therefore low. Some samples did, however, contain enterohaemorrhagic E. coli virulence properties, such as Stx1, Stx2 and enterohaemolysin, which might impose a health risk if ingested.

The occurrence of hepatitis A and astroviruses in selected river and dam waters in South Africa.

Over a period of one year (June 1997-May 1998) samples of surface waters, used for domestic and recreational purposes, were collected weekly from the same sites on the Klip River and Vaal Dam, Gauteng, South Africa. Sensitive and specific reverse transcriptase-polymerase chain reaction-oligonucleotide probe assays were used to detect HAV and HAstV RNA in concentrates of the water and infectious virus in cell cultures infected with the water concentrates. HAV was detected in 18 (35.3%) of the river and 19 (37.3%) of the dam water samples, often in association with the RNA from other enteric viruses. HAstV was detected less frequently and was present in 11 (21.6%) of the river and 3 (5.9%) of the dam water samples. A seasonal pattern was noted for HAV but not for HAstV. Cell culture amplification in a variety of carefully selected cell culture systems enhanced the detection of both viruses. Infectious viruses were detected in dam water samples where microbiological indicators of faecal pollution were absent or within acceptable limits. The presence of these viruses in the dam and river water could pose a potential health risk for people using these waters for domestic or recreational purposes.

New methods for the detection of viruses: call for review of drinking water quality guidelines.

Drinking water supplies which meet international recommendations for source, treatment and disinfection were analysed. Viruses recovered from 100 L-1,000 L volumes by in-line glass wool filters were inoculated in parallel into four cell culture systems. Cell culture inoculation was used to isolate cytopathogenic viruses, amplify the nucleic acid of non-cytopathogenic viruses and confirm viability of viruses. Over a period of two years, viruses were detected in 23% of 413 drinking water samples and 73% of 224 raw water samples. Cytopathogenic viruses were detected in 6% raw water samples but not in any treated drinking water supplies. Enteroviruses were detected in 17% drinking water samples, adenoviruses in 4% and hepatitis A virus in 3%. In addition to these viruses, astro- and rotaviruses were detected in raw water. All drinking water supplies had heterotrophic plate counts of < 100/mL, total and faecal coliform counts of 0/100 mL and negative results in qualitative presence-absence tests for somatic and F-RNA coliphages (500 mL samples). These results call for a revision of water quality guidelines based on indicator organisms and vague reference to the absence of viruses.

Detection and rapid differentiation of human enteroviruses in water sources by restriction enzyme analysis.

The objective of this study was to assess the application and efficiency of molecular techniques for the detection and serotyping of enteroviruses from environmental water samples. Samples of water were collected at regular intervals upstream and downstream of an informal settlement. Techniques for the detection of enteroviruses included a reverse transcription polymerase chain reaction (RT-PCR), nested PCR (n-PCR) and Sabin-specific triplex PCR. A specific 297 bp fragment was amplified by the n-PCR and subjected to restriction enzyme (RE) analysis to differentiate between various serotypes of prototypical enteroviruses. Enteroviruses that gave inconclusive restriction patterns were typed by partial sequencing of the VP1 region. Results indicated a high incidence of enteroviruses, predominantly coxsackie B viruses. The results on polioviruses, as well as other enteroviruses, contributed valuable information on enteroviruses circulating in the community. The molecular approach described here proved suitable for the rapid, sensitive, specific and cost effective, simultaneous detection and typing of enteroviruses in water.

Evaluation of a rapid test for HIV antibodies in saliva and blood.

OBJECTIVE: To test whole blood and saliva for HIV antibodies (anti-HIV) using a rapid test strip capillary flow immunoassay, and to correlate the test strip results with blood specimen results obtained from routine diagnostic anti-HIV assays. DESIGN: A prospective pilot study of selected HIV-positive and HIV-negative individuals, children and medico-legal cases from Gauteng, South Africa. METHODS: Whole blood specimens taken from every individual and medico-legal case (total study population 153) and saliva specimens taken from 76 selected cases were tested for anti-HIV using the respective Hema-Strip HIV-1/2, Sero-Strip HIV-1/2 and Saliva-Strip HIV-1/2 (Saliva Diagnostic Systems Inc.) rapid test strip methodology. All results were correlated with the currently recommended anti-HIV assays. RESULTS: The whole blood test strip results correlated 100% with the traditional diagnostic results. Only two saliva test strip results tested false-negative, both from marasmic and severely dehydrated babies, while the other results were in concordance. All test strip results on postmortem blood and saliva were fully concordant with the diagnostic assay results. CONCLUSION: The anti-HIV test strip methodology for whole blood and saliva specimens is rapid, reliable and easy to perform and interpret. Saliva specimens can be readily collected from any individual, and there is a reduction in hazard risk. Anti-HIV saliva testing using the test strip methodology is recommended for South Africa, particularly in high-risk situations such as the paediatric and forensic medicine settings. A large field study obtaining specimens from different regions in South Africa is advised.

Elimination of viruses, phages, bacteria and Cryptosporidium by a new generation Aquaguard point-of-use water treatment unit.

The elimination of human viruses, phages, bacteria and Cryptosporidium oocysts by a new generation commercial Aquaguard purifier for the domestic treatment of drinking water, has been evaluated. The unit basically consists of a candle prefilter, activated carbon filter and ultraviolet irradiation compartment. Drinking water seeded with selected laboratory test strains of resistant micro-organisms was passed through the unit. Similar tests were carried out with sewage-contaminated river water and secondary treated waste water containing naturally occurring organisms. Test procedures were based on internationally accepted principles for the evaluation of point-of-use water treatment units, including a standard test protocol of the United States Environmental Protection Agency. Reduction in numbers of seeded test organisms at several log levels higher than those expected in water for which the unit is intended, was determined by the cultivation of viable organisms. In the case of seeded viruses and Cryptosporidium parvum oocysts the qualitative absence of nucleic acid was determined by the reverse transcriptase polymerase chain reaction (RT-PCR). At the design flow rate of one litre per minute, numbers of polio, hepatitis A, adeno types 2 and 41, rota SA11, human rota and astro viruses, as well as somatic and MS2 coliphages, and Escherichia coli, Streptococcus faecalis, Clostridium perfringens, total coliform bacteria, enterococci, heterotrophic bacteria and C. parvum oocysts, were reduced by more than 99.999% in all waters tested. This efficiency conforms to specifications for such units. The quality of the treated water was well within microbiological limits of international specifications for drinking water.