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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03503

    Bacteriological and histopathological analysis of Penaeus vannamei experimentally infected with Vibrio parahaemolyticus strains

    K. G. Aguilar-Rendón, R. Lozano-Olvera, B. Yáñez-Rivera, S. A. Soto-Rodriguez*

    *Corresponding author:

    ABSTRACT: Vibrio parahaemolyticus strains have been identified as the causative agent of acute hepatopancreas necrosis disease (Vp AHPND+) of shrimp. In the present work, a highly virulent (M0904) and less virulent (M0607) strain of Vp AHPND+ were used in experimental infections of Penaeus vannamei. During the experimental infections, histopathological analysis was done, and samples from the bottom (B) and water column (WC) of each aquarium were taken to estimate the bacterial growth. The first deaths of shrimp challenged with Vp M0904 occurred at four h post-infection (p.i.), reached 50% mortality at 17 h p.i., and showed more acute pathological progression associated with AHPND, despite both strains having similar bacterial densities from 0 to 4 h p.i. The first deaths of shrimp inoculated with Vp M0607 occurred at 13 h p.i., a delay of nine h. These shrimps displayed reduction of reserve vacuoles in R and B cells of the hepatopancreas, and reached 50% shrimp mortality at 27 h p.i. As the bacterial growth in WC and B in the first hours was similar for both strains, bacterial density was not a significant factor of Vp virulence. As pirAB toxin is the causative agent of AHPND, it is possible that there is a threshold level at which the toxin damages hepatopancreatic tissues and so, production or secretion of the toxin can be dependent of the Vp strain. We propose stage of remission as a new AHPND stage, where hepatopancreatic embryonic (E) cells can be used as a biological indicator of the stage.