Depuration Investigation on Parasites and Bacterial Loads in Freshwater Clam (Batissa violacea) and Oyster (Crassostrea gigas) Using a Sand Filter and UV Radiation.

Freshwater clams (Batissa violacea) and oysters (Crassostrea gigas) are popular and important socioeconomic food security commodities that are commercially available to both locals and the hotel industry. Clams and oysters are consumed with various levels of preparation, ranging from raw to fully cooked. This study examined the presence and levels of bacterial and parasitic contaminants in freshwater clams and oysters from selected sites in Fiji and subjected them to depuration with a sand filter setup under ultraviolet (UV) and non-UV conditions for 50 h. Compared to the non-UV setup, the UV setup was significantly better in reducing total plate counts (TPC), coliforms, and fecal coliform (FC) for clams and FC and Vibrio spp. for oysters. The UV system had overall better performance; however, the non-UV setup also had effective performance. Multiple parasites were present in both oysters and clams. Elevated levels of FC and Vibrio spp. in both clams and oysters are a serious concern for food safety. The depuration system remained ineffective against parasites. Overall, depuration is an economical and effective system for the removal of bacterial contaminants from freshwater clams and oysters while keeping the animals in healthy and live condition. PRACTICAL APPLICATIONS: (1) Clams and oysters have a substantial undesirable biotic load in their bodies, which includes pathogens, heterotrophs, and parasites. (2) Depuration with sand filter and UV light setup effectively reduces TPC, coliform, fecal coliform, and Vibrio spp. loads from clams and oysters to safe levels for consumption.