No abstract

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. , and in the dam water as 3AE12 · 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.

The risk of infection constituted by enteroviruses detected in drinking water supplies analysed in this study were assessed. Coxsackie B viruses (CBV) were used as a model in these assessments. A high proportion of Coxsackie B virus infections are asymptomatic. However, clinical manifestations may range from mild, undifferentiated febrile illness or upper respiratory tract infection to a severe, systemic and sometimes fatal disease of sensitive populations. Dose-response studies suggested that an exponential model best describes infectivity of CBV. The analysis of 172 samples of treated drinking water supplies described in this study revealed the presence of CBVs in 11% (water treatment unit A) and 16% (water treatment unit B) of the samples. This incidence of CBV was used as a basis for risk assessment. The results indicated that the drinking water supplies concerned constitute a risk of CBV infection of 3.91 × 10-3 (unit A) and 7.4 × 10-3 (unit B) per year. The estimated risk of infection are about an order of magnitude higher than the yearly acceptable risk of one infection per 10,000 consumers proposed for drinking water supplies.

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.

Giardia spp. and Cryptosporidium spp. are recognized worldwide as highly infectious protozoan parasites that can cause severe gastrointestinal disease in humans and animals. The detection of these pathogens in activated sludge samples becomes interesting since there is an increasing trend for the use of sewage sludge (biosolids) in agriculture. A total of 22 samples were collected and evaluated by means of Centrifugal -Concentration, followed or not followed by a purification process (ether clarification and sucrose flotation). Student t tests for comparison of the two procedures indicated a higher recovery rate of Giardia cysts with Centrifugal -Concentration; with regard to Cryptosporidium oocysts, no significant differences were found between the two methods, as only two samples were positive. The Centrifugal -Concentration procedure was shown to be the simplest and cheapest to perform, as emphasized by the efficiency recovery results.