Enteric Viruses And Aquatic Environment

摘要

Enteric viruses are mostly found in a variety of aquatic reservoirs including ground water, sewage water, streams, rivers and marine water. They are associated with health risks and responsible for variety of infections in humans. Enteric viruses existence varied greatly in the aquatic environment and also depends upon human activities. Traditional water quality indicators like bacterial coliforms provide no information regarding enteric viruses load in different types of water samples. Environmental water samples are analyzed by a variety of analytical methods for the detection and monitoring of enteric viruses. The virus particles in environment samples are concentrated by adsorption/elution protocols, ultrafiltration or ultra-centrifugation prior to isolation or detection. In spite of the limitations for each method traditional cell culture infectivity assay and molecular biology tools like nucleic acid amplification, microarray based assay or combination of cell culture and polymerase chain reaction are used as valuable informative tool to detect enteric viruses in aquatic environment. INTRODUCTION Water borne diseases have great socioeconomic impacts on public health all around the world. Natural water is a complex mixtures of inorganic, organic compounds and macro-organisms. Swage water comprises of different substance originates from industrial, commercial and residential activities. It also carries different chemicals toxic wastes and biological infectious agents of fungal, bacterial and viral origins. Enteric viral pathogens presence in waste water is important with public health perspective(Bosch, 1998). Enteric viruses commonly cause gastroenteritis and mostly transmitted through the fecaloral route. They include different group of viruses present in human intestinal tract and responsible for different illnesses like fever, meningitis, hepatitis, rashes and respiratory diseases. They are divided in to a number of different families including Picornaviridae (polioviruses, coxsackieviruses, echoviruses, enteroviruses and hepatitis A virus), Adenoviridae (adenoviruses), Reoviridae (reoviruses and rotaviruses), and Caliciviridae (noroviruses, caliciviruses, and astroviruses) (Wilhelmi et al., 2003).Although some enteric viruses have been found in the aquatic environments there is still a lack of comprehensive indicator system for monitoring of these organisms (Wyn Jones et al., 2011). These viruses have the ability to survive for a longer time (130) days and remain infectious at lower doses. They are discharged continuously to environment from their hosts (Fong and Lipp, 2005).The monitoring of enteric viruses in different aquatic environments would be helpful to assess the risk of human exposures. In aquatic environment the quantification of these viruses is difficult technically, requires a long time and is expensive. In fact, the viruses of primary concern are difficult or impossible to quantify. Therefore, many public agencies rely on bacterial indicator organisms to establish a quality However, they are not correlated with the occurrence of enteric viruses (Parkin et al., 2003). The main problems with bacterial indicators are, they do not reflect the presence for other pathogens, such as viruses and parasites, they do not depict the fact that many pathogens reproduce in the environment after being excreted by their host (Fong and Lipp, 2005). In some cases, where assays have been within the limits recommended for bacterial indicators in water, human enteric viruses have been found at dangerously high concentrations. Current microbial indicators (e.g. enterococci, fecal streptococci and fecal coliform bacteria) simply do not give information on the viral quality of water (Ehlers et al., 2005). Other studies suggest the use of alternative indicators of viral pathogens, such as bacteriophages, (Ogorzaly et al., 2009), or adenoviruses (Wyn Jones et al., 2011). But still there is no consensus on the best indicator for v