The development and implementation of a method using blue mussels (Mytilus spp.) as biosentinels of Cryptosporidium spp. and Toxoplasma gondii contamination in marine aquatic environments

Surveillance monitoring for microbial water quality typically involves collecting single discrete grab samples for analyzing only one contaminant. While informative, current approaches suffer from poor recoveries and only provide a limited snapshot of the microbial contaminants only at the time of collection. To overcome these limitations, bivalves have been proposed as effective biosentinels of water quality particularly for their ability to efficiently concentrate and retain microbial contaminants for long periods of time. In this study, we examined the use of indigenous blue mussels (Mytilus spp.) as biosentinels to monitor for the presence of Toxoplasma gondii and Cryptosporidium water. An efficient method to extract oocyst DNA from various mussel tissues followed by PCR-based detection of these pathogens was developed, which resulted in the detection down to 10 oocysts. This method was then used to conduct a small survey in Point Lobos and Morro Bay, California to determine prevalence T. gondii and Cryptosporidium. Results revealed that mussels from Morro Bay were contaminated with T. gondii (33 %), while mussels from Point Lobos were contaminated with T. gondii (54 %) and Cryptosporidium (26.9 %) oocysts. Phylogenetic analysis using the SSU rRNA gene identified two novel Cryptosporidium parvum-like genotypes. Overall, this study demonstrated the application of using native California Mytilus spp. as biosentinels for pathogen contamination along the central California shorelines. More importantly, T. gondii and Cryptosporidium were found at higher prevalence rates in Morro Bay and in Point Lobos, an area not previously reported to be contaminated with these pathogens.