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Global Warming and Trans-Boundary Movement of Waterborne Microbial Pathogens - Book Chapter
Citation:
ASHBOLT, N. Global Warming and Trans-Boundary Movement of Waterborne Microbial Pathogens - Book Chapter. Chapter 5, Sumi, A., Fukushi, K. and Hiramatsu, A. Tokyo (ed.), In Adaptation and Mitigation Strategies for Climate Chang. Springer, New York, NY, , 71-82, (2010).
Impact/Purpose:
Potential ramifications of climate change, as they reklate to waterborne pathogens (primarily viruses, bacterial & parasitic protozoa), are the focus of this chapter. It seems clear that climate change will impact on waterborne pathogens in various ways (Rose et al. 2001), pertinent to transboundary issues are: 1) increases in intense storm events (increasing sewage/animal waste flows into waterways/aquifers) (Charron et al. 2004; Schijven and de Roda Husman 2005; Yang and Goodrich 2008; De Toffol et al. 2009; Richardson et al. 2009); 2) warmer surface water temperatures or salinity changes (for increased autochthonous pathogen growth) (Niemi et al. 2004; Koelle et al. 2005; Lebarbenchon et al. 2008); and 3) changes in food production, as most obvious in animal diseases (Lightner et al. 1997; Rapoport and Shimshony 1997), but also of concern with zoonoses and from changes in social behavior (Schwab et al. 1998; Nancarrow et al. 2008; CDC 2009a). When considering trans-boundary effects on waterborne pathogens, it is therefore the flow of pathogens in surface water (fresh & marine) and in groundwater, as well as in the varying ways water is used/reused in association with human activities (e.g. food production) that are the transboundary issues discussed in this chapter (examples in Table 1). Changes in infectious and vector-borne diseases associated with rising sea levels, losses of habitat, international travel etc. are not addressed in this chapter.
Description:
Subtle increases in temperature can have profound impacts on the prevalence of various waterborne microbial pathogens. Such impacts may be seen in three major areas, 1) fecally contaminated drinking water, 2) fresh produce that has been irrigated or processed with contaminated water, and 3) seafood where pathogens and microbial toxins are present. Each of these areas is influenced by rainfall events, which have a fundamental influence on the fate and transport of pathogens. Temperature alone can also impact, as seen with the epidemic strains of cholera (disease from certain Vibrio cholerae bacteria). In coastal environments, cholera outbreaks associate with particular phytoplankton blooms in nutrient-enriched coastal waters; with blooms varying due to changing precipitation regimes and El Niño. A further ecological interaction is seen by bacteriophage mediated cholera toxin genes inserted into non-toxic V. cholerae strains. For microorganisms, boundaries occur at the tens of micron scale, with most terrestrial microbes living in slime on surfaces (biofilm). As ambient water temperatures increase, there is a clear increase in the growth of biofilms and their associated pathogens, many of which appear to be amoeba associated. Most opportunistic bacterial pathogens (such as strains of Aeromonas, Legionella, Mycobacterium) and even frank, fecally-derived pathogens (e.g. Campylobacter jejuni, Cryptosporidium parvum, and enteric viruses) have been observed to accumulate within biofilm amoeba. With rising temperatures and increased application of recycled waters, biofilm pathogens will be presenting a range of pathogen challenges to communities. Human behavior is also influenced by climate change, with increased consumption of uncooked foods and water during warmer conditions, as well as increased travel (trans-boundary transport of pathogens). Increased rainfall events also promote zoonotic diseases (e.g. cryptosporidiosis, E. coli O157:H7 infections) via contamination of drinking water sources and water used to irrigate crops.