Factors affecting sporoplasm release in Kudoa septempunctata.

The myxosporean parasite Kudoa septempunctata has been isolated from cultured olive flounder (Paralichthys olivaceus) and was recently identified as a cause of food poisoning in humans. Since the sporoplasm plays an important role in causing diarrhea by invading intestinal cells, the specific factors affecting the release of sporoplasm from spores should be determined. Thus, we investigated the effect of digestive and serum enzymes, fetal bovine serum (FBS), temperature, and the role of glucose in cell culture media on the release of sporoplasm. Sporoplasm release was observed in the groups treated with FBS and media containing glucose. In addition, 1,10-phenanthroline inhibited the release of sporoplasm in the FBS medium. These results indicate that K. septempunctata uses glucose for releasing its sporoplasm and that zinc or metalloprotease is related to the release mechanism. The present study provides important information for the development of agents to prevent sporoplasm release and the consequent food poisoning caused by K. septempunctata.