Evaluation of F-RNA coliphages as indicators of viruses and the source of faecal pollution

Abstract

It is a growing concern that analyses of true indicators of pathogenic viruses have not been properly established. Water treatment and catchment management strategies based on bacteriological indicators do not provide the necessary protection against viral infections because viruses are more persistent than bacteria in water environments. More than 100 types of human pathogenic viruses may be present in faecally polluted water, but only a small number can be detected by currently available methods. Analysing for enteric viruses such as the polio and hepatitis viruses is specialised and is neither practical nor commercially viable for a water utility. Human enteric viral disease is considered to be predominantly associated with human wastes, as opposed to animal wastes, and a distinction between these is desirable. Somatic coliphages are not always present whenever enteric viruses were detected and have been found to multiply in the environment outside the body. It has previously been shown that for monitoring purposes, F-specific RNA bacteriophages are model organisms and suitable indicators of the possible presence of human pathogenic enteric viruses as they behave like waterborne viruses. F-specific bacteriophages have been suggested as a useful alternative to the traditional bacterial indicators as their morphology and survival characteristics closely resemble those of some of the important human enteric viruses. F-specific RNA phages are becoming the indicators of choice for viruses in water and have been accepted as one of the rapid screening tests to determine the quality of water. Studies have shown that based on hybridisation tests, F-RNA coliphages could be associated with either a human or animal source. F-RNA coliphages have been grouped into four groups with Groups 2 and 3 being of human origin and Groups 1 and 4 originating from animals. This study aimed to fulfil the requirement of both developing a relatively simple method for F-RNA coliphage analyses in samples from the Umgeni Water catchment and further testing to elucidate whether the contamination was of animal or human origin using gene hybridisation techniques to type the F-RNA phages. The standard ISO method for the isolation of F-RNA coliphages was used and genotyping assays were performed according to methods adapted by the University of Pretoria’s Medical Virology Department. Highly specific nucleic acid probes for the detection of F-specific RNA bacteriophages were used in this study to fingerprint the origin of faecal pollution. The E. coli data generated for the sample sites indicated that certain sites tended to have more faecal pollution problems than others. Somatic coliphages were isolated in numbers as high as 1 100 pfu.10 ml -1 and were consistently isolated in higher numbers than F-RNA coliphages. The strongest positive correlation (r = 0.842) was between E. coli and F-RNA coliphage concentrations. The F-RNA coliphages isolated from one river sample and wastewater works effluent hybridised with the GA probe belonging to Group 2, which was of human origin.