HomeMy WebLinkAboutShellfish Sampling Presentation 120518Newport Bay Shellfish Study
Presentation to the
Water Quality/Tidelands Committee
December 4, 2018
Bob Stein, Public Works Department
Assessing Shellfish Contamination:
Study Question
Is monitoring for viral and bacterial pathogens in shellfish a
more reliable method for assessing contamination of shellfish by a sewage source as compared to using an indicator such as
fecal coliform or coliphage?
Background
•Newport Bay Fecal Coliform (FC) TMDL adopted in 1999
•Included in the TMDL is the objective to restore shellfish
harvest beneficial use:
•Monthly median not to exceed 14 MPN/100 mL
•Not more than 10% exceed 43 MPN/100 mL
•BMPs have improved water quality but not anything close to
the TMDL standards.
Fecal Coliform Indicator
•Fecal Coliform (FC) is not an appropriate indicator for shellfish safety at Newport Bay
•There are continuous input of significant FC loadings from non-fecal
sources:
Urban runoff (2 large tributaries, large and small drains)
Birds, wildlife, domestic animals
Natural sources
Regrowth
Is FRNA Coliphage an Appropriate Indicator of
Shellfish Safety?
•Coliphages: viruses that infect E. coli bacteria
•F-specific coliphage (FRNA) have been used to indicate virus contamination of drinking water
•FRNA are commonly found in sewage, less frequently in animal feces
•FRNA phage have been used as indicators of norovirus contamination in shellfish (Flannery et al. 2009)
•However, FRNA levels in water do not always correlate with viruses
•Jiang et al. (2007) found no correlation between F+ coliphage with
adenovirus and enterovirus in Newport Bay
Direct Testing of Pathogens in Shellfish
•Fecal coliforms and coliphage do not consistently correlate with pathogens in shellfish.
•The safest approach to assess shellfish safety is to test directly for pathogens, such as Norovirus and other viral pathogens (e.g. adenovirus and enterovirus) and bacterial pathogens (e.g. Salmonella & E. coli 0157).
•Norovirus are among the most common human pathogens in shellfish
•Humans are the only known host of NoV; thus, their presence in shellfish indicate human fecal contamination.
•NoV have been among the most important pathogen related to outbreaks involving shellfish.
•NoV do not replicate in shellfish.
Why Not Test for Norovirus and Pathogens in
the Water Column?
•Testing water for pathogens is challenging
•Viruses (and other pathogens) in source waters can occur at very low levels requiring filtering 10 – 100 liters of water to find detectable levels
•Shellfish are naturally occurring filters
•Cultured bivalve mollusks can filter 1 to 4 liters/hour
Why test for pathogens other than Novovirus?
•Norovirus are more specific (but maybe not 100% specific) to human fecal waste; however, lab methods are based on detecting molecular targets and there is limited data on correlating quantity of virus
copies with illness rates
•Salmonella & E. coli 0157 have also been found in shellfish
•Culture methods are available to detect actual organisms (versus molecular target); unlike molecular methods that detect DNA targets from dead organisms
Shellfish Collection
Team
Collection
Attire
5/8/18 Samples Taken at Coast Highway Bridge
Collected mussels are put on
blue ice and shipped in a
Styrofoam box overnight to a
laboratory certified to test
for viral and bacterial
pathogens.
May 21,
2018
Sampling
August 13,
2018
Sampling
August 27,
2018
Sampling
Positive for
Samonellat
Santa Ana-
Delhi
Channel
Correlation between Fecal Coliform in Water
Column vs. Shellfish?
•How well do FC and FRNA levels in water correlate with pathogen levels in shellfish?
May 21,
2018
Sampling
Final Thoughts
•City is currently funding the sampling and analyses. We would like the OC Watershed stakeholders to participate.
•Regional Water Quality Control Board is looking to change the TMDL
standard for shellfish from FIB to ??? How can we coordinate the
programs?
•Certified laboratories for pathogen testing must be used!
Ensure we don’t have shellfish impacted by sewage
Provide data as a basis for legal defense.