Source: UNIV OF CALIFORNIA (VET-MED) submitted to
CRYPTOSPORIDIUM IN BIVALVES AS INDICATORS OF FECAL POLLUTION IN THE CALIFORNIA COASTAL ECOSYSTEM
Sponsoring Institution
Cooperating Schools of Veterinary Medicine
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0194679
Grant No.
(N/A)
Project No.
CALV-UCWATER01-W963
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Jul 1, 2002
Project End Date
Jun 30, 2004
Grant Year
(N/A)
Project Director
Conrad, P. A.
Recipient Organization
UNIV OF CALIFORNIA (VET-MED)
(N/A)
DAVIS,CA 95616
Performing Department
PATHOLOGY, MICROBIOLOGY & IMMUNOLOGY
Non Technical Summary
Bivalves such as clams and mussels have been shown to concentrate Cryptosporidium oocysts, thus acting as indicators of fecal pollution in aquataic ecosystems. The results of this study will be highly significant in watershed management and minimizing the impact of fecal pollutants in our coastal ecosystems.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3130812104010%
3130812107010%
3130812109010%
3130812111010%
3130812117010%
7220812104010%
7220812107010%
7220812109010%
7220812111010%
7220812117010%
Goals / Objectives
The freshwater, estuarine and nearshore marine waters of California are highly utilized but only minimally monitored and understood with regard to human pathogens. Cryptosporidium is a widespread fecal pathogen that has caused many waterborne epidemics of diarrheal disease in people. It was recently documented for the first time in marine mammals along the California coast. No studies have yet been conducted to investigate the magnitude and sources of Cryptosporidium contamination in California waters. This study will be the first to evaluate the aquatic epidemiology of Cryptosporidium along the California coast.
Project Methods
This is a two year study. In year one we will sample bivalves at 50 sites along the California coast including freshwater, estuarine and nearshore marine sites to map out the hot spots for Cryptosporidium contamination. The second year will target the ten most contaminated sites for further investigation of potential pollution sources, as indicated by the Cryptosporidium genotypes we detect and identification of possible pollution sources in the vicinity of bivalve collections sites. This study will be the first to evaluate the aquatic epidemiology of Cryptosporidium along the California coast.

Progress 07/01/02 to 06/30/04

Outputs
The goal of this study was to evaluate bivalve clams and mussels as bioindicators of fecal protozoan contamination using 3 approaches: 1) bivalve tissue spiking experiments to compare several detection techniques, 2) tank exposure experiments to evaluate bivalves that that had filtered Cryptosporidium oocysts from inoculated water under a range of simulated environmental conditions, and 3) sentinel bivalve outplanting to assess the distribution and magnitude of fecal contamination in riverine, estuarine, and nearshore marine ecosystems in California. Our spiking and tank experiments showed that immunofluorescent and DNA amplification techniques could be used to detect Cryptosporidium in bivalve tissues and that immunomagnetic beads could be used to concentrate parasites from bivalve tissues. In the tank experiments, oocyst dose and bivalve collection time were found to be significant predictors for detecting C. parvum oocysts in bivalve tissues. In the sentinel bivalve study, Cryptosporidium and Giardia were detected in clams from all 3 riverine study regions, with significant variation by sampling year and season. The presence of C. parvum DNA in clam tissues was confirmed with PCR and sequence analysis and could have come from human or animal sources of fecal contamination. At estuarine and nearshore marine study sites, Cryptosporidium were detected in mussels from sites considered at higher risk and at lower risk for fecal contamination. Genotypes detected in mussels included C. felis and C. andersoni that are shed in the feces of cats and cattle, respectively. In addition to these host-specific genotypes, C. parvum was also detected in mussel batches and could have come from human or animal fecal sources. Exposure to freshwater outflow and precipitation in the week preceding mussel collection were the most significant risk factors for Cryptosporidium detection in mussels. This study has shown that filter feeding bivalves can be used as bioindicators of fecal pollution in freshwater and nearshore marine ecosystems in California, and has provided important clues regarding the risk factors and contributing sources of fecal pollution.

Impacts
This project has important implications for the management of fecal pathogens in wastewater and runoff from both urban and farming areas, as well as for nearshore animals such as marine mammals and shellfish.

Publications

  • Miller, W.A., Atwill, E.R., Gardner, I.A., Miller, M.A., Fritz, H.M., Hedrick, R.P., Melli, A.C., Barnes, N.M., and Conrad, P.A. 2005. Clams (Corbicula fluminea) as bioindicators of fecal contamination with Cryptosporidium and Giardia spp. in freshwater ecosystems of California. International Journal for Parasitology, In Press.


Progress 01/01/03 to 12/31/03

Outputs
Cryptosporidium spp. are zoonotic protozoa that causes diarrheal disease and are shed in the feces of many animals and humans in California. Bivalves such as mussels (Mytilus spp.) and clams (Corbicula spp.) are plentiful in salt and freshwater coastal California ecosystems, respectively, and can be efficiently tested for Cryptosporidium using molecular techniques optimized in the investigators laboratories. These techniques were first validated using tank exposure experiments for mussels and clams. They were then applied to mussels and clams that were out-planted at sites considered at higher risk and at lower risk for fecal pollution. Cryptosporidium and Giardia were detected in mussels and clams out-planted at higher risk sites but not at lower risk sites, with a higher prevalence in the wet season than the dry season. Agencies charged with species management, food safety, and water quality may benefit from these pathogen detection assays and risk assessment methods.

Impacts
This project has important implications for the management of fecal pathogens in wastewater and runoff from both urban and farming areas, as well as for nearshore animals such as marine mammals and shellfish.

Publications

  • No publications reported this period


Progress 01/01/02 to 12/31/02

Outputs
The objective of this study is to obtain critical data on the epidemiology of Cryptosporidium in freshwater, estuarine, and nearshore marine ecosystems along the California coast, to assess the magnitude of fecal pathogen contamination, and to identify potential contributing sources of these pollutants. Bivalves may be sensitive and practical water quality monitoring tools for fecal pollution because they are found in many aquatic ecosystems, concentrate pathogenic protozoa such as Cryptosporidium, and retain these elevated Cryptosporidium levels over the subsequent days and weeks. We are testing the following two hypotheses: 1) Cryptosporidium species are present in Pacific coast bivalves collected at sites exposed to fecal contamination, including sites near human sewage outfalls and livestock runoff, and 2) Cryptosporidium genotypes will differ significantly in bivalves collected at sites exposed to human fecal contamination (e.g. near sewer discharge sites) compared with bivalves collected at sites contaminated with livestock feces (e.g. downstream from agricultural runoff). We have tested bivalves from freshwater, estuarine, and nearshore marine sites located near livestock runoff (high impact sites), human sewage outfalls (high impact sites), or more than 5 km from both livestock and human sewage impacts (low impact sites). Cryptosporidium DNA has been detected in wild mussels (Mytilus californianus) from high impact sites along the California coast, but not from mussels collected at low impact sites during the wet and dry seasons. Freshwater clams (Corbicula) are being evaluated as bioindicators of fecal pollution in freshwater ecosystems.

Impacts
The results of this study may help guide optimal watershed management in efforts to minimize the impact of fecal pollutants in our coastal California ecosystems.

Publications

  • No publications reported this period