Pathogenic agents in freshwater resources

Abstract

Numerous pathogenic agents have been found in freshwaters used as sources for water supplies, recreational bathing and irrigation. These agents include bacterial pathogens, enteric viruses, several protozoans and parasitic worms more common to tropical waters. Although infected humans are a major source of pathogens, farm animals (cattle, sheep, pigs), animal pets (dogs, cats) and wildlife serve as significant reservoirs and should not be ignored. The range of infected individuals within a given warm-blooded animal group (humans included) may range from 1 to 25%. Survival times for pathogens in the water environment may range from a few days to as much as a year (Ascaris, Taenia eggs), with infective dose levels varying from one viable cell for several primary pathogenic agents to many thousands of cells for a given opportunistic pathogen.As pathogen detection in water is complex and not readily incorporated into routine monitoring, a surrogate is necessary. In general, indicators of faecal contamination provide a positive correlation with intestinal pathogen occurrences only when appropriate sample volumes are examined by sensitive methodology.Pathways by which pathogens reach susceptible water users include ingestion of contaminated water, body contact with polluted recreational waters and consumption of salad crops irrigated by polluted freshwaters. Major contributors to the spread of various water-borne pathogens are sewage, polluted surface waters and stormwater runoff. All of these contributions are intensified during periods of major floods. Several water-borne case histories are cited as examples of breakdowns in public health protection related to water supply, recreational waters and the consumption of contaminated salad crops. In the long term, water resource management must focus on pollution prevention from point sources of waste discharges and the spread of pathogens in watershed stormwater runoff.

Campylobacter spp. , Giardia spp. , Cryptosporidium spp., Noroviruses, and Indicator Organisms in Surface Water in Southwestern Finland, 2000-2001

“…In some studies a significant correlation has been found between the level of thermotolerant coliforms and the number of samples positive for certain pathogens (4,34). However, a poor correlation similar to that shown in the present study has also been demonstrated elsewhere (8, 14,26,43). The presence or absence of a correlation between fecal indicators and pathogens could reflect the occasional appearance of enteropathogens in surface waters and the different rates of survival and recovery of the pathogens compared with those of fecal indicators.…”

“…The presence or absence of a correlation between fecal indicators and pathogens could reflect the occasional appearance of enteropathogens in surface waters and the different rates of survival and recovery of the pathogens compared with those of fecal indicators. One possible factor affecting the low correlation could also be different microbial densities in the original contamination sources, and therefore, the failure to detect pathogens was due to sampling volumes that were too small (14,17). For detection of Giardia spp.…”

Salmonellae in the Environment

“…Together, these and other studies suggest that faecal indicators are potentially a useful warning of the potential presence of salmonellae in aquatic environments (Geldreich, 1996). However, relationships are not always found between faecal indicators and salmonellae in aquatic environments; an observation that may be related to various reasons such as different survival rates between salmonellae and faecal indicators, also the possibility that salmonellae being in a viable but nonculturable state.…”

Long-term and short-term variations of Escherichia coli population structure in tropical coastal waters

“…Faecal pollution in rivers has been reported in Malaysia (Law 1980;Kenzaka et al 2001). The main sources of faecal contamination are poultry manure, agricultural runoff, industrial waste, poorly treated or untreated sewage from urban areas and other anthropogenic input (Geldreich 1996;Ferguson et al 2003;Wilkinson et al 2006). As shown by the correlation coefficient, salinity explicated about 22 % of change in coliform counts, therefore, other factors, e.g.…”

“…Faecal pollution can be introduced from multiple sources, e.g. agricultural runoff, industrial waste, inadequately treated sewage from urban areas and other anthropogenic input (Geldreich 1996;Ferguson et al 2003).…”