W.O.K. Grabow

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.

Incidence of adenoviruses in raw and treated water

Adenoviruses are of major public health importance and are associated with a variety of clinical manifestations, i.e. gastroenteritis, eye infections and respiratory infections. The importance of water in the epidemiology of adenoviruses and the potential health risks constituted by adenoviruses in water sources and supplies are widely recognised. This study was conducted to assess the incidence of human adenoviruses in raw and treated water systems. Various raw and treated water were routinely monitored for the presence of adenoviruses, over a 1-year period (July 2000-June 2001). The supplies were derived from acceptable quality surface water sources using treatment processes, which conform to international standards for the production of safe drinking water. Adenoviruses were detected by firstly amplifying the viruses in cell cultures and then amplifying the extracted nucleic acids of these viruses using molecular techniques (nested PCR). The results indicated human adenoviruses present in 13 (12.75%) of the raw and 9 (4.41%) of the treated water samples tested. The combination of cell culture and nested PCR has proved to be a quick and reliable method for the detection of adenoviruses in water environments.

Incidence of human calicivirus and rotavirus infection in patients with gastroenteritis in South Africa

Human caliciviruses (HuCVs) are reportedly responsible for 2.5–4% of nonbacterial sporadic gastroenteritis. The incidence of HuCV infection in South Africa is unknown. Stool specimens from 1,296 South African patients with sporadic gastroenteritis were screened for the presence of HuCVs using electron microscopy, recombinant enzyme immunoassays for Norwalk (NV) and Mexican (MX) viruses, and the reverse transcriptase‐polymerase chain reaction (RT‐PCR). RT‐PCR products were sequenced to ascertain which HuCV genogroups were present. HuCVs were detected in 43/1,296 (3.3%) specimens examined, with RT‐PCR proving to be the most sensitive detection method. Genetic analysis of the isolates indicated that 81% were Snow Mountain Agent, or MX‐like; 8% were NV‐like; and 11% were HuCV/Sapporo‐like. This study indicates that a combination of assays is needed for the accurate detection of HuCVs. Comparative data on hospitalised patients showed that the incidence of rotavirus infection was approximately ten times greater than that of HuCV infection. J. Med. Virol. 51:290–296, 1997.

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.

Molecular Epidemiology of Group A Rotaviruses in Water Sources and Selected Raw Vegetables in Southern Africa

ABSTRACT 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.

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.

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.

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.

Propagation of adenovirus types 40 and 41 in the PLC/PRF/5 primary liver carcinoma cell line.

The sensitivity of cell cultures to adenovirus types 40 and 41 (Ad40/41) was compared by means of cell culture infectious dose (ID50) assays using monolayer cultures in microtitre plates. The PLC/PRF/5 cell line derived from a primary human hepatocellular carcinoma was 100 times more sensitive to a laboratory strain of Ad41, and 10 times more sensitive to a laboratory strain of Ad40 and two Ad41 stool isolates, than Graham 293 and Chang conjunctival cells commonly used for the propagation of these viruses. In microtitre plate titration assays PLC/PRF/5 cells retained an optimal condition for longer and displayed cytopathogenic effects earlier and more clearly than the other cell lines. In contrast to previously used cells, PLC/PRF/5 cells also proved successful for the quantitation of Ad41, but not Ad40, by conventional plaque assays. The reason for the exceptional susceptibility of PLC/PRF/5 cells has not been elucidated, but the findings open attractive new doors for research on Ad40/41.

Rotavirus, astrovirus and adenovirus associated with an outbreak of gastroenteritis in a South African child care centre

An outbreak of gastroenteritis in the infant-toddler unit of a child care centre (CCC) in Pretoria, South Africa, was investigated for possible viral enteropathogens. Rotavirus was found in association with seven (70%) diarrhoeal episodes. Co-infection with rotavirus and human astrovirus (HAstV) was demonstrated in two of these episodes, and rotavirus, HAstV and enteric adenovirus (EAd) co-infection in another. Rotavirus occurred alone in four of the diarrhoeal episodes, while HAstV and EAd were each detected alone in one episode. Two HAstV and one rotavirus asymptomatic infection episodes also occurred. Overall, 8 of 10 children had rotavirus infections, of which 7 were symptomatic, 6 of 10 children had HAstV infections (4 symptomatic), and 2 of 10 children had EAd infection, both symptomatic. These results highlight the diversity of viral enteropathogens that may be associated with a diarrhoeal outbreak in a CCC and emphasize the need to investigate the possibility that multiple enteropathogens may simultaneously cause a single outbreak of diarrhoea.