California Sea Grant College Program

Cryptosporidium spp. are protozoan parasites that cause gastrointestinal disease in humans and animals, and are spread directly by fecal-oral transmission or indirectly by fecal contamination of water and food supplies. In California, there is evidence of significant fecal pathogen pollution flowing from terrestrial to aquatic ecosystems along the coast. To develop ecosystem monitoring and management strategies, we tested the hypothesis that Cryptosporidium spp. are detectable in nearshore filter feeding bivalves and in terrestrial storm runoff collected from fecal-impacted coastal ecosystems in California. The goals of this dissertation research were 1) to evaluate innovative detection methods for Cryptosporidium spp. in bivalve and water samples, 2) to evaluate bivalves such as mussels and clams as bioindicators of fecal contamination with Cryptosporidium spp. in marine, estuarine, and freshwater ecosystems, and 3) to evaluate farm management solutions to reduce the load of Cryptosporidium discharged into downstream waterways from coastal dairies. First, innovative molecular and immunologic methods were evaluated for detection of Cryptosporidium spp. in marine mussels (Mytilus californianus) and freshwater clams (Corbicula fluminea) using tissue spiking and tank exposure experiments. The most analytically sensitive detection method was immunomagnetic separation in combination with immunofluorescent detection of oocysts in mussel digestive tissues. Second, field studies tested 4800 mussels and 600 clams from marine, estuarine, and riverine ecosystems along the California coast forCryptosporidium spp. Genotypes detected in bivalves included the anthropozoonotic C. parvum genotype 2, as well as the host specific C. andersoni and C. felis that are shed by cattle and cats, respectively. In addition, 2 novel Cryptosporidium genotypes were detected in mussels. Third, a 3-year study evaluated the distribution of Cryptosporidium on coastal dairies and the efficacy of various farm management practices to reduce the load of Cryptosporidium oocysts in storm runoff. Calves were found to be important loading sources of Cryptosporidium on the farms, and vegetative buffers were found to effectively reduce the load of Cryptosporidium oocysts in storm runoff. In conclusion, Cryptosporidium spp. were detected in terrestrial runoff and nearshore bivalves, suggesting that Cryptosporidium spp. will be useful bioindicators of fecal contamination in ecosystem monitoring and management programs.