Seasonal occurrence of the pathogenic Vibrio sp of the disease of sea urchin Strongylocentrotus intermedius occurring at low water temperatures and the prevention methods of the disease

To obtain fundamental data to prevent the disease of sea urchins Strongyloc entrotus intermedius occurring at low water temperatures, an ecological sur vey on the causative bacterium, Vibrio sp. was carried out for one year at monthly intervals in 1996 at Date City Fisheries Breeding Center. The causa tive bacterium of the disease was detected in samples of seawater, on the s urface of sea urchins and on rearing cages throughout the year. It was pres umed that sea urchins suffered from injury or breakdown when they were gath ered for handling of selection for shipping and consequently the disease oc curred through invasion of the causative Vibrio into the coelome, To preven t this disease, effects of treatments with higher temperature, disinfectant s, drugs and ultraviolet irradiation were examined by using two representat ive causative Vibrio strains Da-2 and Sr-3. Pathogenicity in experimental i nfection of both strains at 20 degreesC were similar to those at 11 degrees C. They showed high sensitivity to benzyl penicillin and erythromycin, but were resistant to cloxacillin, spiramycin and chemotherapeutics. Their susc eptibilities to ultraviolet irradiation were higher than that of causative bacterium Flexibacter sp. of spotting disease. Moreover, among the eight di sinfectants tested in vitro, treatment with a 500 ppm chlorine dioxide for 30 min at 15 degreesC was found to significantly disinfect the bacteria wit hout any injury to the sea urchins.