Appendix A
Emerging and Reemerging Waterborne Pathogens

This appendix addresses a requirement of the committee’s statement of task; specifically the requirement to “. . . define currently known waterborne pathogen classes and anticipate those emerging waterborne pathogens that are likely to be of public health concern.” For the purposes of this report, emerging and reemerging pathogens can be defined as recently identified waterborne pathogens or those pathogens that were once thought to be under control from a public health perspective but are reappearing and causing increased incidence or geographic range of infections in exposed human populations. In recent years, several such waterborne pathogens have arisen, including recognized pathogens from fecal sources and some “new” pathogens from environmental sources. Several factors contribute to the (re)emergence of waterborne pathogens in the United States (Theron and Cloete, 2002), including the following:

  • Changes in human demographics. There is an increasing number of “vulnerable subpopulations” in the United States such as infants, children, pregnant women, the elderly, and the immunocompromised (e.g., AIDS patients) who are particularly susceptible to infections resulting from exposure to waterborne pathogens compared to the general populace (see also NRC, 2001).

  • Changes in human behavior. Urbanization of rural areas allows infections arising in formerly isolated areas, which may once have remained obscure and localized, to reach large and densely populated areas. The use of heated drinking water with warm water reservoirs also promotes the emergence of waterborne pathogens because these systems are ideal habitats for a number of pathogens of public health concern, such as Legionella spp. (Lee and West, 1991).



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Indicators for Waterborne Pathogens Appendix A Emerging and Reemerging Waterborne Pathogens This appendix addresses a requirement of the committee’s statement of task; specifically the requirement to “. . . define currently known waterborne pathogen classes and anticipate those emerging waterborne pathogens that are likely to be of public health concern.” For the purposes of this report, emerging and reemerging pathogens can be defined as recently identified waterborne pathogens or those pathogens that were once thought to be under control from a public health perspective but are reappearing and causing increased incidence or geographic range of infections in exposed human populations. In recent years, several such waterborne pathogens have arisen, including recognized pathogens from fecal sources and some “new” pathogens from environmental sources. Several factors contribute to the (re)emergence of waterborne pathogens in the United States (Theron and Cloete, 2002), including the following: Changes in human demographics. There is an increasing number of “vulnerable subpopulations” in the United States such as infants, children, pregnant women, the elderly, and the immunocompromised (e.g., AIDS patients) who are particularly susceptible to infections resulting from exposure to waterborne pathogens compared to the general populace (see also NRC, 2001). Changes in human behavior. Urbanization of rural areas allows infections arising in formerly isolated areas, which may once have remained obscure and localized, to reach large and densely populated areas. The use of heated drinking water with warm water reservoirs also promotes the emergence of waterborne pathogens because these systems are ideal habitats for a number of pathogens of public health concern, such as Legionella spp. (Lee and West, 1991).

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Indicators for Waterborne Pathogens Breakdown of public health systems. Although public health measures such as water and wastewater treatment act to minimize human exposure to waterborne pathogens and reduce the incidence of waterborne disease, these systems can and do fail on occasion—often with extensive public health ramifications. Such breakdowns also provide opportunities for pathogens to reemerge. Microbial adaptation. Microbes are constantly evolving in response to changing environments and environmental conditions. With the increasing use and release of antibiotics and drugs into our waterways, strains of microorganisms that are antibiotic- or drug-resistant have also been increasingly identified (see Chapter 3 for further information). Changes in agricultural practices. Intensive farming operations (especially concentrated/confined animal feeding operations, or CAFOs) result in high concentrations of animal wastes, which in turn lead to increased pollution of our nation’s waters by runoff and intentional (point source) discharges. This is of public health concern because a number of pathogens (e.g., Cryptosporidium) routinely contained in such fecal sources can be transmitted to humans through inadequately treated drinking water or through recreational water exposure. Throughout this report, waterborne pathogens (including those that can be considered emerging or reemerging) can be categorized into four groups: viruses, bacteria, protozoa, and others. (“Others” include cyanobacterial toxins and protists; however, this group is not discussed extensively in this report for reasons outlined in Chapter 1.) Indeed, Chapter 3 on the ecology and evolution of waterborne pathogens and indicator organisms is divided into separate sections for viruses, bacteria, and protozoa. The issue of new and (re)emerging waterborne pathogens has been reviewed in several published reports and articles (EPA, 1998; LeChevallier et al., 1999; Szewzyk et al., 2000; Theron and Cloete, 2002) from a public health and/or water treatment perspective. Therefore, in response to the statement of task, this appendix includes a brief summary of the health effects and mode of transmission of select emerging and reemerging waterborne pathogens in all four groups taken from these and other sources (see Table A-1). Lastly, several of the waterborne pathogens listed in Table A-1 are discussed to some extent (in some cases extensively) elsewhere in this report. REFERENCES EPA (U.S. Environmental Protection Agency). 1998. Announcement of the Drinking Water Contaminant Candidate List; Notice. Federal Register 61(94): 24354-24388. Hilton, C., K. Holmes, K. Spears, L.P. Mansfield, A. Hargreaves, and S.J. Forsythe. 2000. Arcobacter, newly emerging food and waterborne pathogens. Presentation at SGM Warwick, April 12. LeChevallier, M.W., M. Abbaszdegan, A.K. Camper, G. Izaguirre, M. Stewart, D. Naumovitz, M. Mardhall, C.R. Sterling, P. Payment, E.W. Rice, C.J. Hurst, S. Schaub, T.R. Slifko, J.B. Rose, H.V. Smith, and D.B. Smith. 1999. Emerging pathogens: Names to know and bugs to watch out for. Journal of the American Water Works Association 91(9): 136-172.

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Indicators for Waterborne Pathogens Lee, J.V., and A.A. West. 1991. Survival and growth of Legionella species in the environment. Journal of Applied Bacteriology Symposium Supplement 70: 121S-129S. NRC (National Research Council). 2001. Classifying Drinking Water Contaminants for Regulatory Consideration. Washington, D.C.: National Academy Press. Szewzyk, U., R. Szewzyk, and K.H. Schleifer. 2000. Microbiological safety of drinking water. Annual Review of Microbiology 54: 81-127. Theron, J., and T.E. Cloete. 2002. Emerging waterborne infections: Contributing factors, agents, and detection tools. Critical Reviews in Microbiology 28: 1-26.

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Indicators for Waterborne Pathogens TABLE A-1 Emerging and Reemerging Waterborne Pathogens of Public Health Concern Waterborne Pathogen Health Effects Mode of Transmission References and URLs Viruses Adenoviruses Respiratory infections; gastroenteritis; febrile (fever-related) disease with conjunctivitis Fecal-oral transmission; waterborne transmission http://www.ce.berkeley.edu/~nelson/ce210a/Adenovirus/CE210a-adenovirus-k.htm; http://www.cdc.gov/ncidod/dvrd/revb/respiratory/eadfeat.htm; EPA, 1998 Astrovirus Diarrhea Fecal-oral transmission Szewzyk et al., 2000 Coxsackieviruses Diarrhea and vomiting; skin rashes; myocarditis and pericarditis (inflammation of the heart tissue and the membranous sac enveloping the heart, respectively); aseptic meningitis Person-to-person transmission; fecal-oral transmission; contaminated water, particularly recreational water http://www.awwarf.com/newprojects/pathogens/COXSACKI.html; EPA, 1998 Echoviruses Subclinical infections; myocarditis; aseptic meningitis Fecal-oral route EPA, 1998 Enteroviruses Gastroenteritis; poliomyelitis (inflammation of the gray matter of the spinal cord); meningitis; respiratory disease; diabetes; encephalitis (inflammation of the brain) Fecal-oral route or respiratory route LeChevallier et al., 1999; Theron and Cloete, 2002 Hepatitis viruses Gastroenteritis Fecal-oral route; fecally contaminated water and food; person-to-person transmission LeChevallier et al., 1999 Norwalk/Caliciviruses Diarrhea and vomiting Contaminated surface water, groundwater, ice; contaminated shellfish; swimming in water containing sewage EPA, 1998; LeChevallier et al., 1999 Rotavirus Diarrhea Fecally contaminated surface water Szewzyk et al., 2000; Theron and Cloete, 2002

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Indicators for Waterborne Pathogens Bacteria Arcobacter Diarrhea Drinking water reservoirs and treatment plants Hilton et al., 2000 Aeromonas hydrophila Gastroenteritis Drinking water biofilms EPA, 1998; Theron and Cloete, 2002 Campylobacter (including C. jejuni, C. coli, and related species) Acute gastroenteritis Contaminated poultry products; unpasteurized milk; water LeChevallier, et al., 1999; Szewzyk et al., 2000; Theron and Cloete, 2002 Helicobacter pylori Gastroduodenal disease including chronic active gastritis; peptic and duodenal ulcer disease; gastric cancer Unknown; fecal-oral transmission is highly probable EPA, 1998; LeChevallier et al., 1999; Theron and Cloete, 2002 Legionella spp. Legionnaires disease (severe lung inflammation) and Pontiac fever (influenza-like form of disease) Source water to drinking water Szewzyk et al., 2000 Mycobacterium avium complex Pulmonary disease Drinking water treatment and distribution system EPA, 1998; LeChevallier et al., 1999 Pathogenic Escherichia coli Hemorrhagic colitis (bleeding from inflamed colon) with bloody diarrhea and hemolytic-uremic syndrome (acute illness following a respiratory infection causing bloody diarrhea) Contact with contaminated beef or dairy products LeChevallier et al., 1999; Szewzyk et al., 2000; Theron and Cloete, 2002 Pseudomonas aeruginosa Nosocomial infections (infections associated with hospital stays) in immunocompromised patients and patients with underlying diseases such as wound and urinary tract infections and pneumonia; tracheobronchitis in cystic fibrosis patients Water exposed to fecal contamination; surface waters influenced by wastewater discharge; nutrient-rich water Szewzyk et al., 2000 Yersinia enterocolitica Gastrointestinal infections Unknown; contaminated food and water are the most likely sources Szewzyk et al., 2000; Theron and Cloete, 2002

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Indicators for Waterborne Pathogens Waterborne Pathogen Health Effects Mode of Transmission References and URLs Protozoa Acanthamoeba Granulomatous amoebic encephalitis (swelling of the brain characterized by granulation tissue) in immunosuppressed people; keratitis (severe and potentially blinding infection of the cornea) Contamination of contact lens or storage case http://www.awwarf.com/newprojects/pathegeons/ACANTHAM.html; EPA, 1998 Cryptosporidium parvum Subclinical infections and self-limiting diarrhea in healthy adults; severe diarrhea in infants and immunocompromised persons Drinking water Szewzyk et al., 2000; Theron and Cloete, 2002 Cyclospora cayetanensis Diarrhea, abdominal cramping, decreased appetite, and low-grade fever that can last for several weeks Unknown; fecal-oral route either directly or via water is thought to be highly probable LeChevallier et al., 1999 Giardia lamblia Subclinical infections and self-limiting diarrhea in healthy adults; severe diarrhea in infants and immunocompromised persons Drinking water Szewzyk et al., 2000; Theron and Cloete, 2002 Microsporidia Diarrhea and cholangiopathy (infection of bile ducts) in immunocompromised persons Surface water; sewage-contaminated waters EPA, 1998; LeChevallier et al., 1999; Szewzyk et al., 2000 Toxoplasma gondii Flu-like illness and/or swollen glands in the neck, armpits, or groin Water contaminated by cats LeChevallier et al., 1999 Other Cyanobacteria toxins Poisoning; gastrointestinal disease Nutrient-rich surface water EPA, 1998; LeChevallier et al., 1999; Szewzyk et al., 2000