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GLOBAL WARMING AND TRANS-BOUNDARY MOVEMENT OF WATERBORNE MICROBIAL PATHOGENS
Citation:
ASHBOLT, N. GLOBAL WARMING AND TRANS-BOUNDARY MOVEMENT OF WATERBORNE MICROBIAL PATHOGENS. Presented at International Symposium on Dialogue between Social and Natural Sciences, Honolulu, HI, February 26 - 28, 2007.
Impact/Purpose:
To provide broad-based support for the Microbiological and Chemical Exposure Assessment Research Division and to facilitate outreach and communications with peers, stakeholders, clients, and the public.
Description:
Subtle increases in temperatures 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 waters; 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 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 waters used to irrigate crops.