Waterborne Pathogens
The potential for contamination of the Regional Water Supply by waterborne pathogens poses a direct risk to human health. Because the Water Department does not currently filter its water supply, watershed management is an important method for protecting water quality at the source. Therefore, potential sources and exposure pathways of pathogens need to be managed in the watershed to minimize the likelihood of contamination in the reservoirs. Elevated levels of pathogens in a water supply increase the risk of waterborne disease. A cleaner water source can also reduce the need for excess chlorination, which has been associated with other health risks (Lawton, 1999).
Humans are the primary source of waterborne pathogens; however, infected domestic animals and wildlife can also be sources of pathogenic organisms (Schaub and Roberson, 1997; Rand, n.d.). Potential routes of exposure from human or animal faeces to the water supply include run-off from roads, changing water levels in streams and the
reservoir shoreline, and direct defecation into the reservoir (Aramini et al., 1997). Vegetation in the drawdown area of Sooke Reservoir emerges during the summer and fall, attracting animals into this high risk area. Roads in the watershed area used by animals and humans have also been shown to be a potential route of contamination (Aramini et al., 1997).
Pathogenic micro-organisms in surface water supplies can include parasites (e.g., Giardia, Cryptosporidium), viruses (e.g., Hepatitis A, coxsackieviruses), and bacteria (e.g., E. coli, Salmonella, Shigella) (Fox, 1999; Schaub and Roberson, 1997). Giardia and Cryptosporidium are among the most widespread protozoan pathogens causing diarrhea and gastro-intestinal problems in humans worldwide (Smith and Lloyd, 1998).
The degree of illness ranges from asymptomatic in some people to life-threatening in immuno-compromised individuals (e.g., people with AIDS). Toxoplasma gondii is a more specific parasite that is only transmitted to humans through the faeces of domestic and wild cats, such as cougars. After a cyst is ingested, the disease called toxoplasmosis is usually asymptomatic in most people, but can cause birth defects and serious or fatal disease in immuno-compromised individuals (Aramini et al., 1997). E. coli and other bacteria can cause bacillary disentery and gastro-intestinal illness (Schaub and Roberson,
1997).