The increase in shrimp farming practices has resulted in the eutrophication of lagoon systems and the emergence of infectious diseases. Acute Hepatopancreatic Necrosis Disease (AHPND) is a bacterial type of disease that continuously causes ravages in culture ponds. Although it is known that a vast number of bacteria are associated with this disease, strains of Vibrio parahaemolyticus have been identified as carriers of the pVA1 plasmid, the causative agent.
In this study, an experimental infection was performed with Vibrio campbellii strain M270210, which harbors the same pVA1 plasmid, to observe its capacity to cause the disease and compare its virulence against the V. parahaemolyticus strain M0904, reported as highly virulent. Furthermore, we performed a challenge in which both strains were simultaneously inoculated in Mpc to test whether or not the mortality of shrimps would be affected compared to the individual treatments. Penaeus vannamei shrimp weighing 300 (±0.005) mg obtained from a larval production laboratory (UPL) in Rosario Sinaloa were acclimatized for one week. These were subsequently exposed through a bath challenge with three treatments: V. parahaemolyticus (Vp) strain M0904, V. campbellii (Vc) strain M270210, and simultaneous exposure to both strains (Mpc). First mortalities were observed at five h, nine h, and six h post-inoculation (hpi), respectively. A 50% survival (Kaplan-Meier estimator) was calculated at 13, 21, and 16 hpi, respectively.
All of the organisms challenged presented the characteristic symptoms of AHPND. By the end of the experiment, significant differences were found between Mpc and Vc (p=0.049) and between Vp and Vc (p=0.21) but not between Vp and Mpc (p=0.71). These results suggest some antagonistic effect between both bacterial strains because the combined inoculation of strains (Mpc treatment) showed a delay in mortality compared to the inoculation of only V. parahaemolyticus (Vp treatment).