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Emerging Pathogens

Technical Document

Introduction

The Safe Drinking Water Act (SDWA) requires the EPA to prioritize contaminants for future regulation based on public health risks, particularly to vulnerable populations (Section 1412(b)). The SDWA also requires the EPA to periodically (every 5 years) publish a list of contaminants not currently subject to regulation, but are known or anticipated to occur in public water systems and which may require future regulation¹. To accomplish this, the EPA developed the drinking water Contaminant Candidate List (CCL). The first was published in the Federal Register on March 2, 1998. The CCL serves as the primary source of priority contaminants for the EPA’s drinking water program. Contaminants on the list may be selected for possible regulation, guidance development, health advisories, future research, and/or monitoring programs. It should be noted that the CCL is a notice and not a regulatory action.

Regarding the list of microbiological contaminants on the CCL, the EPA generally did not include microorganisms that have not caused (or are not expected to cause) a waterborne outbreak in the United States, or those considered susceptible to filtration and/or disinfection¹.

Organisms included on the CCL are listed in the table below.

Other groups have identified additional emerging pathogens including pathogenic Escherichia coli and Campylobacter jejuni (bacteria), hepatitis A virus (virus), and Cyclospora cayetanensis and Toxoplasma gondii (protozoa)².

Research Needs

Additional research is needed on CCL microbes and other emerging pathogens. Research topics include sample collection and analytical methods, the occurrence and distribution of these microorganisms in water, routes of exposure, susceptibility of the human population, the microbial dose necessary to cause disease, and resistance to treatment¹.

Current Efforts at ASI

In response to these research needs as well as client requests, ASI’s staff has begun developing and testing analytical procedures for several emerging pathogens. Projects are currently underway in our laboratories on protozoa, bacteria and viruses. Propagation of Cyclospora cayetanensis oocysts and Microsporidia (Enterocytozoon bieneusi and Encephalitozoon intestinalis) spores constitute a significant focus of ASI’s emerging pathogen research efforts.

Various detection techniques, including traditional methods such as cell culture and advanced molecular techniques like Polymerase Chain Reaction (PCR), are being evaluated. For example, ASI is currently optimizing a multiplex PCR procedure to detect enteroviruses (the poliovirus, echovirus and coxsackie virus groups), rotavirus and hepatitis A virus in a single analysis. In addition, ASI performs Integrated Cell Culture/Reverse Transcriptase-PCR (ICC/RT-PCR) which allows the detection of only infectious viral particles. However, methods for these microorganisms are currently at the experimental stage, and validated protocols do not yet exist.

We are also examining and evaluating the efficiency of various means of collection and concentration of emerging pathogens from the environment. For example, Aeromonas hydrophila has been included in the EPA’s proposed (April 1999) Unregulated Contaminant Monitoring Rule (UCMR) which requires assessment monitoring beginning in January, 2001.

Plans to perform drinking water treatment unit (DWTU) performance validation including disinfectant efficacy and filter efficiency studies using select emerging pathogens are underway. We are continuing this research with the expectation of offering microbiological testing of several emerging pathogens in the near future.

References

1. EPA. Announcement of the Drinking Water Contaminant Candidate List. EPA-815-Z-98-001. Fed. Reg., 63:10273-10287 (1998).

2. LeChevallier, M.W. 1998. Committee report: Emerging Pathogens: Names to Know and Bugs to watch out for." Microbial Contaminant Research Committee, Amer. Water Works Assoc.

Relevant Literature

1. Marshall, M.M., et al. 1997. Waterborne Protozoan Pathogens. Clin. Microbiol. Rev., 10:67-85.

2. Reynolds, K.A. 1998. Reducing Occupational Risks of Microbial Contaminants in Water. Water Cond. & Purif., 40:60-65.

3. Friedman-Huffman, D. and Rose, J.B. 1998. Waterborne Pathogens: Emerging Issues, Emerging Treatments – A Review. Water Cond. & Purif., 40:48-53.

4. Centers for Disease Control. 1996. "Surveillance for Waterborne Disease Outbreaks, United States, 1993-1994" Morbidity & Mortality Weekly Report. 45:22-1.

5. Centers for Disease Control. 1990. "Viral Agents of Gastroenteritis," Morbidity & Mortality Weekly Report. 39:RR-5.

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