UC Marine Council
Cryptosporidium in Bivalves as Indicators of Fecal Pollution in the California Coastal Ecosystem
- Author(s): Miller, Woutrina
- et al.
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The California coastal ecosystem is highly impacted by fecal pollution from sewage outfalls, agricultural runoff, and urban stormwater runoff. In the past, water quality monitoring has focused on toxins and bacterial coliform counts. However, this methodology does not address the public health threat of zoonotic protozoal parasites or allow for the identification of pollution sources.
Cryptosporidium species are pathogenic protozoal parasites that are shed by both humans and animals, are endemic in the California livestock populations, have a low infective dose, and have environmentally stable oocysts that can be spread via contaminated water. The diarrheal disease cryptosporidiosis is especially threatening to the immunocompromised population such as AIDs patients. Cryptosporidium has been documented in wildlife along the California coast but no studies have yet investigated the magnitude and sources of this pathogen in the marine environment.
Bivalves, such as clams and mussels, concentrate Cryptosporidium oocysts, thus acting as indicators of fecal pollution. Bivalves can be efficiently tested for Cryptosporidium using a Real-Time PCR technique that we recently developed. The assay can detect the DNA of a single organism and gives a quantitative result. This method can also be used to differentiate between Cryptosporidium species and genotypes from animal and human sources.
Our preliminary studies show that Cryptosporidium DNA is detectable in wild bivalves collected off the California coast. We propose a two year study: the first year will sample bivalves at 20 sites along the coast to map out the hot spots of Cryptosporidium contamination. The second year will target the 10 most highly contaminated sites for further investigation into the probable sources of contamination, as indicated by the Cryptosporidium genotypes and the possible pollution sources located near the collection sites. The results of this study will be very valuable in watershed management and minimizing the impact of fecal pollutants on our coastal ecosystems.