BOX 3-1
Summary of Important Ecological and Evolutionary Questions That May Affect the Understanding of Various Indicators for Waterborne Pathogens and Infectious Diseases

  1. What is the distribution and abundance of waterborne pathogens? Are these environmental reservoirs of pathogens biotic or abiotic?

  2. What are the fates of freshwater pathogens when imported into marine or brackish waters?

  3. Is the residence time of a pathogen sufficient to allow genetic exchange or change to occur?

  4. What biotic and abiotic factors influence the viability and survivability of waterborne pathogens? Are there environmental conditions that promote genetic exchange or the acquisition of genetic elements that confer selective advantage under clinical conditions?

  5. What effect do sampling and environmental variations have on the efficacy of indicators?

forces begin to act on these introduced or exotic microorganisms, whether eukaryotes or prokaryotes.

This chapter describes basic principles of ecology and evolution for waterborne viruses, bacteria, and protozoa (and yeasts and molds to a lesser extent) of public health concern as an aid to better understand how selective forces may alter one’s ability to assess the microbial quality of water. Indeed, indicators of microbial water quality can be the pathogenic organisms themselves, other microorganisms, or other physical or chemical aspects of the aquatic environment (see Chapter 4 for further information), and any biological indicator is subject to evolutionary and ecological changes. The final section is a summary of the chapter and its conclusions and recommendations.

Answers to several sets of related and fundamental questions (summarized in Box 3-1) are imperative to facilitate the understanding of indicators of waterborne pathogens and emerging infectious diseases. These questions include but are not limited to the following:

  1. What is the natural distribution and abundance of waterborne pathogens? Are there environmental reservoirs of these microorganisms and, if so, what environmental conditions promote their maintenance or growth? Are these environmental reservoirs biotic or abiotic (i.e., from the living or nonliving)? Can waterborne pathogens colonize and proliferate in sediments or within aquatic systems? The concepts of growth and regrowth are most often applied to water distribution systems and wastewater discharges (and their receiving waters), respectively.

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