Develop Methodology to Identify and Characterize Caliciviruses and Sources of Human Pathogens in Water

2003 Research Abstracts - Table of Contents

National Exposure Research Laboratory - FY03 Research Abstract

Scientific Problem and Policy Issues

The Safe Drinking Water Act, as amended in 1996, requires EPA to develop a list of unregulated microbiological and chemical contaminants to aid in setting priorities for the Agency's drinking water program. The initial list of contaminants, called the Contaminant Candidate List (CCL), was published in 1998 in the Federal Register (63 FR 10274). Caliciviruses were included in this list because they have been responsible for drinking water-related outbreaks of acute gastroenteritis in the U.S. Caliciviruses are divided into four genera— Norovirus, Sapovirus, Vesivirus and Lagovirus. Vesiviruses and lagoviruses infect only animals. Sapoviruses infect humans, but are genetically and physically closely related to the two animal genera. Noroviruses are the major cause of waterborne disease as they are highly infectious to people of all ages. Recently, norovirus strains were discovered in cattle with diarrhea. This discovery led to concern about the possible zoonotic spread of these viruses between cattle and humans.

Research Approach

The study's objectives were to determine if any sapovirus or norovirus strains are present in local Ohio cattle herds and to determine the relationship of any strains found to known human noroviruses. The approach was to examine pooled fecal samples from local herds using a molecular assay. For samples that contain viruses, this molecular assay produces many DNA copies of a part of the virus genome. These DNA copies were then sequenced. Because the sequences of the virus genomes are unique for different strains, those found in the fecal samples of local herds could be used 1) to prove that a positive result was really caused by a sapovirus or a norovirus, and 2) to show the relationship of the strains found to other animal and human strains.

Results and Impacts

The molecular assay was used to screen RNA extracted from pooled fecal samples from four veal calf herds. Noroviruses were found in three of the herds and sapoviruses in four. The sequences that were found in these samples were used to improve the molecular assay, and the modified assay was used to test 75 veal calf fecal samples. 72% of these were positive for noroviruses. A subset of 21 of the positive samples was sequenced and confirmed to be human-like noroviruses. This study shows that noroviruses are frequently found in Ohio cattle herds. Although the strains that were found were very similar to human strains, they were not identical and are likely to be bovine-specific. However, zoonotic transmission from cattle to humans cannot be ruled out.

This research project directly supports ORD's efforts to improve the scientific foundation for safe drinking water. The results of this research support the Government Performance and Results Act Goal 2 ("Clean and Safe Water"), Objective 2.1 ("Ensure Safe Drinking Water and Recreational Waters"), and Sub-Objective 2.1.7 Long Term Goal 2 ("By FY 2010, develop new data, innovative tools and improved technologies to support decision making by the Office of Water on the Contaminant Candidate List and other regulatory issues, and implementation of rules by states, local authorities and water utilities"). It was done in support of an FY03 GPRA annual performance goal ("The Office of Water will have data, methods, assessments and technology evaluations necessary to support scientifically sound risk assessment and risk management decisions on unregulated contaminants of potential public health concern") and annual performance measure #101 ("Develop methodology to identify and characterize H. pylori, caliciviruses and sources of human pathogens in water").

Research Collabortation and Research Products

This research was performed under a collaborative agreement with the Ohio State University.

The findings of this research have been published (Publication No. NERL-CI-MCEARD-02-059):

Smiley, J.R., A.E. Hoet, M. Traven, H. Tsunemitsu and L.J. Saif. 2003. Reverse transcription-PCR assays for detection of bovine enteric caliciviruses (BEC) and analysis of the genetic relationships among BEC and human caliciviruses. J. Clin. Microbiol. 41, 3089-3099.

Future Research

An important outcome of this study is the finding that some molecular assays designed to detect human noroviruses in environmental waters can also detect the bovine strains. Laboratories analyzing these waters need to take this into account and modify the assays to minimize this source of potentially false-positive results. Additional research may be needed to verify that the modifications are sufficient.

Contacts for Additional Information

Questions and inquiries can be directed to:
G. Shay Fout, Ph.D.
US EPA
National Exposure Research Laboratory
Cincinnati, OH 45268
Phone: 513/569-7387
E-mail: fout.shay@epa.gov

2003 Research Abstracts - Table of Contents

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