Evaluation of the diagnostic reliability of the gill-based Ray’s fluid thioglycollate medium assay for Perkinsus olseni infections in Manila clams (Ruditapes philippinarum) across Korean tidal flats

A study evaluating the diagnostic reliability of gill-based Ray’s fluid thioglycollate medium (RFTM) assays for detecting Perkinsus olseni infections in Manila clams across Korean tidal flats found that while gills are a strong proxy for whole-body infection in high-prevalence areas, their accuracy drops significantly in low-infection environments. The research analyzed six tissues from clams collected at six sites, revealing that the visceral mass consistently harbored the highest parasite loads (27.8%-49.0%), followed by the mantle and gills. At most sites, gill infection levels correlated strongly with whole-body infection intensity (r²=0.6-0.95), but at Padori—where infection prevalence was lowest—the gill assay's efficacy plummeted to 56%, leading to a 44% false negative rate. These findings highlight the limitations of relying solely on gill tissue for diagnostic purposes and advocate for a dual-tissue approach combining gill and whole-body samples to enhance accuracy in surveillance efforts.

Cho, Y.-G., Nobuhisa, K., Choi, H. J., Kwon, M.-G., Yang, H.-S., & Choi, K.-S. (2025). Evaluation of the diagnostic reliability of the gill-based Ray’s fluid thioglycollate medium assay for Perkinsus olseni infections in Manila clams (Ruditapes philippinarum) across Korean tidal flats. Parasites, Hosts and Diseases, 63(2), 157–167. https://doi.org/10.3347/phd.25014