Foodborne Illness Case Detected Unicapsula seriolae by PCR-Based Test to Detect A Wide Range of 18S Ribosomal RNA Gene of Genus Kudoa

Abstract

In April 2018 in Toyama Prefecture, cases of foodborne illnesses possibly caused by Kudoa septempunctata were reported from eating raw flounder, amberjack, and tuna sashimi. Leftover foods and feces from two of the patients were immediately tested for K. septempunctata, but there were none detected. Therefore, we suspected the presence of myxosporean other than K. septempunctata. We performed a PCR-based test with specific primers, developed by us, to detect a wide range of 18S ribosomal DNA (rDNA) from the genus Kudoa and Unicapsula. In one of the leftover foods, amberjack sashimi, we detected Unicapsula seriolae (U. seriolae) 18S rDNA using another set of specific primers. Two rounds of PCR amplification were carried out on DNA from stool samples of the patients using both primer sets to detect 18S rDNA of the genus Kudoa or of U. seriolae. Lastly, 18S rDNA of U. seriolae was also detected in feces from the two patients by sequence analysis of the PCR products. Therefore, U. seriolae contamination was predicted to be responsible for illness in the reported cases. Additionally in this study, we were able to demonstrate the use of our PCR primer sets to screen for the genus Kudoa and Unicapsula.