DYNAMICS OF VIBRIO SP PJ IN ORGANS OF ORALLY INFECTED KURUMA PRAWN, PENAEUS-JAPONICUS

Kuruma prawns (Penaeus japonicus) were experimentally infected with Vibrio sp. PJ by the oral administration. At 3, 6, 8, 10, 12, 24, 36, and 48 h post-inoculation, prawns were sampled to determine the cell number and distribution of the pathogen in various organs by viable cell count and the enzyme-labeled antibody technique (ELAT). Vibrio sp. PJ was detected by culture method from the stomach and hemolymph at 3 h and from the hemolymph and almost all the organs sampled at 6 h post-inoculation. However, the pathogen started to disappear from all the organs from 8 h to 12 h. At 12 h, it reappeared in the hepatopancreas and lymphoid organs. Twenty-four hours after inoculation, the pathogen was detected from the hemolymph and all the organs except the stomach and gills, and at 36 h the pathogen was found distributed in all the organs. Principally the same distribution pattern of the pathogen was found by ELAT. These results seem to indicate that the process in the pathogenesis of Vibrio sp. PJ infection in orally challenged kuruma prawns consist of five stages namely, establishment of the pathogen, distribution of the pathogen, clearance of the pathogen by host prawn, secondary multiplication of the pathogen, and systemic infection. The results also suggest that the pathogen multiplied in the stomach in the establishment stage and in the hepatopancreas and lymphoid organs in the secondary multiplication stage.