Emerging Pathogens in Drinking Water
Emerging Pathogens in Drinking Water Abstract: This essay covers the incidence of emerging pathogens in drinking water and the detection methods used to isolate them. For years outbreaks of waterborne diseases have been related to specific pathogens. However in the past 20 years there have been increased reportings that other emerging pathogens are also involved. The lack of detection methods for these microbial organisms has allowed these supposed new pathogens to remain hidden despite the fact that they may have been causing disease for hundreds of years. Both old and new pathogens have been reviewed and the problems that they have or can potentially cause are assessed. One of the habitats, the biofilm, that these organisms colonise is also reviewed and the particular problems that this causes to the water companies. Introduction: It is taken for granted that drinking water will be safe and palatable for human consumption. However there are many problems associated with its safety, which arise due to presence of pathogens. ... The main ‘traditional’ pathogens associated with waterborne transmission in drinking water are Salmonella, Shigella and Escherichia. Much is known about these pathogens and how they cause disease although they still continually pose a problem for water companies in their detection and removal. In the past 20 years however there has also been the identification of several new or ‘emerging’ pathogens,(16) such as, Cryptosporidium parvum, Campylobacter, Aeromonas, and Legionella. The lack of information on how these organisms are causing outbreaks of disease and the new virulence factors that they posses is presenting new complications for the water companies supplying the nations water. Emerging pathogens are often not actually new pathogens but rather old pathogens that have just remained previously undetected. There is a current need to understand how new diseases are able to emerge and why new forms of old pathogens continue to occur. There are varying hypothesis as to why this occurs such as: changes in the host conditions, changes in the genes of the pathogen itself, changes in the water distribution systems,(3) Ecological changes, increase in international travel, microbial adaptation and breakdowns in public health systems.(16) Waterborne pathogens can fall into one of three major categories, bacteria, protozoa or viruses. ... (5) The bacteria contain the largest amount of known pathogens although not necessarily the most pathogenic. Figure1 outlines some of the major characteristics of this class of pathogens. Figure1: Table outlining some of the major waterborne bacterial pathogens to date. ... Infection is caused by inhalation of the organism; the organism can become aerosolised from drinking water by surface breaking. ... Pseudomonas aeruginosa Gram negative, motile Causes an infection called swimmers ear (not transmitted via drinking water) The protozoa are a class of unicellular eukaryotic micro-organisms that lack cell walls. ... Figure 2: Table illustrating some of the major waterborne protozoa in association with drinking water. ... Viruses account for far fewer cases of outbreaks of disease, although they are however present as definite emerging pathogens. Less is known about how these organisms cause infection so the details in figure 3 are only an outline of a few of the present ones which are known to have an effect in drinking water. Figure 3 : An outline of 3 of the most well known virus waterborne pathogens Viruses Rota virus Causes damage by infecting the tips of small intestinal villi resulting in diarrhoea (5) Particularly infectious for infants between 6 and 24 months. ... The main disease resulting from any of the pathogens stated is a gastro-enteritis infection. ... Traditional waterborne pathogens Salmonella typhi – This organism is responsible for up to 100 deaths in the U. ... Standard disinfecting methods should be sufficient to remove the bacteria from water. ... (16) The shigella bacteria has an incredibly low infective dose, of as few as 10 cells (14|) which relates to its long established link with gastro-enteritis due to contaminated drinking waters. ... This surfaces as tissue destruction (14) and is expressed by febrile colitis, and symptoms of dysentery,(15) One particular outbreak that is attributed to contaminated drinking water, occurred in 1995 where visitors to a resort in Idaho experienced severe diarrhoea due to all consuming the same drinking water. ... Coli has long been associated with outbreaks of gastro-enteritis; due to one of the main routes of this infection occurring via drinking water (1).