Clams ( Corbicula fluminea) as bioindicators of fecal contamination with Cryptosporidium and Giardia spp. in freshwater ecosystems in California

• Published in: International journal for parasitology Vol. 35; no. 6; pp. 673 - 684
• Main Authors: Miller, Woutrina A., Atwill, Edward R., Gardner, Ian A., Miller, Melissa A., Fritz, Heather M., Hedrick, Ronald P., Melli, Ann C., Barnes, Nicole M., Conrad, Patricia A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2005; Elsevier Science
• Subjects: Animals; Base Sequence; Biological and medical sciences; Biomarkers - analysis; Bivalve; Bivalvia - parasitology; California; Clam; Cryptosporidium; Cryptosporidium - isolation & purification; Cryptosporidium parvum - genetics; Cryptosporidium parvum - isolation & purification; DNA, Protozoan - analysis; Ecosystem; Fecal pollution; Feces - parasitology; Fluorescent Antibody Technique, Direct - methods; Fresh Water - parasitology; Freshwater; Fundamental and applied biological sciences. Psychology; Giardia; Giardia - isolation & purification; Immunomagnetic Separation - methods; Life cycle. Host-agent relationship. Pathogenesis; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; Molecular Sequence Data; Oocysts - isolation & purification; Polymerase Chain Reaction - methods; Protozoa; Risk Factors; Vectors. Intermediate hosts; Water Pollution; Waterborne pathogens; California; United States; North America; America; Cryptosporidium; Giardia; Fecal pollution; Clam; Bivalve; Waterborne pathogens; Corbicula fluminea; Protozoa; Apicomplexa; Parasite; Biological indicator; Diplomonadida; Contamination; Pollution; Bivalvia; Ecosystem; Walerborne pathogens; Invertebrata; Mollusca
• ISSN: 0020-7519; 1879-0135
• DOI: 10.1016/j.ijpara.2005.01.002

This study evaluated clams as bioindicators of fecal protozoan contamination using three approaches: (i) clam tissue spiking experiments to compare several detection techniques; (ii) clam tank exposure experiments to evaluate clams that had filtered Cryptosporidium oocysts from inoculated water under a range of simulated environmental conditions; (iii) sentinel clam outplanting to assess the distribution and magnitude of fecal contamination in three riverine systems in California. Our spiking and tank experiments showed that direct fluorescent antibody (DFA), immunomagnetic separation (IMS) in combination with DFA, and PCR techniques could be used to detect Cryptosporidium in clam tissues. The most analytically sensitive technique was IMS concentration with DFA detection of oocysts in clam digestive gland tissues, which detected 10 oocysts spiked into a clam digestive gland 83% of the time. In the tank experiment, oocyst dose and clam collection time were significant predictors for detecting Cryptosporidium parvum oocysts in clams. In the wild clam study, Cryptosporidium and Giardia were detected in clams from all three study regions by IMS-DFA analysis of clam digestive glands, with significant variation by sampling year and season. The presence of C. parvum DNA in clams from riverine ecosystems was confirmed with PCR and DNA sequence analysis.