You are here: home » Oceans and Human Health » Pathogen Source Tracking » Detecting Emerging Pathogens » More Information
More Information about the Use of Molecular Techniques to Detect Emerging Pathogens in Coastal Ecosystems
Background
Waters used for recreation and shellfish production are frequently contaminated with human and animal feces that carry protozoan parasites and pathogenic bacteria. Major sources of this contamination include agricultural and urban surface runoff, effluents from malfunctioning water and waste water treatment plants, storm water drainage systems, wastewater discharges, and domestic and wild animals occupying buffer areas surrounding rivers and streams. Pathogenic protozoans that have been reported in estuarine and marine waters, shellfish, and marine mammals and threaten public health include Cryptosporidium sp., Toxoplasma sp., Giardia sp., and Microsporidia. For this Statement of Work, NOAA, the United States Department of Agriculture (USDA), and Center for Disease Control and Prevention (CDC) will collaborate to investigate the presence and prevalence of protist pathogens of public health concern in the coastal environment. These protists were selected for study because they:
- originate from human and animal feces;
- have been reported in shellfish and/or marine mammals;
- do not replicate outside of the host and therefore may serve as indicators of recent fecal contamination; and
- may serve as a potential source of human exposure from individuals involved in water contact recreation or from consuming raw shellfish.
Technology currently does not exist to rapidly and accurately detect and quantify the abundance of the aforementioned protists in water, sediments and shellfish. The major objective of this research will be to develop this biotechnology. Project investigators will also compare the sources of protist pathogens identified by this study with the sources of fecal bacteria contamination identified at the same sample sites. These contrasts should provide a better understanding of the routes of fecal contamination of coastal areas.
Traditionally, microscope- and antibody-based techniques have been used to identify protist pathogens. However, these methods cannot identify the species and⁄or genotypes that specifically infect humans. To identify the species and genotypes of protists that infect humans, molecular technology such as polymerase chain reaction (PCR) and gene sequencing must be applied. For this study, the USDA and CDC will design and evaluate the required biotechnologies, including pathogen-specific primers.
These molecular-based assays, including real-time polymerase chain reaction (RTPCR), will then be calibrated and validated against conventional microscopy using positive and negative controls. In addition, exposure chambers will be spiked with known amounts of the pathogens and the minimum detection levels and recovery of selected pathogens from water, sediment, and shellfish for the new biotechnologies will be determined. Multiple tissues of shellfish will also be assayed with the new biotechnologies to determine the best tissues for field applications. Data from environmental samples will be compared with GenBank listings to determine if specific host sources can be identified.