Identification of potential general markers of disease resistance in Exopalaemon carinicauda via three‐round challenge selection with an acute hepatopancreatic necrosis disease‐causing strain of Vibrio parahaemolyticus

Sixteen candidate disease‐resistant parameters were selected through which to evaluate the acute hepatopancreatic necrosis disease (AHPND)‐resistant capability of Exopalaemon carinicauda after three generations of selection for AHPND‐causing strain of Vibrio parahaemolyticus (VP_AHPND) resistance in our previous study. However, these parameters required further verification. In this study, another AHPND‐resistant E. carinicauda series was obtained through a short‐term selection procedure, consisting of three virulent challenge rounds of selection (about three‐week interval for each challenge) with VP_AHPND infection. After this selection, the survival rate at 144 hr post infection (hpi) increased from 23.33% to 37.78% and the observed 48‐hr LD₅₀ of VP_AHPND to shrimp increased from 10^5.5 cfu/ml to 10^6.5 cfu/ml. Then, the immune response of this AHPND‐resistant E. carinicauda was studied using the 16 candidate AHPND‐resistant parameters selected for in our previous study. The improved VP_AHPND clearance rate in hpi, increased total haemocyte counts, haemocyanin concentration, alkaline phosphatase activity and expressions of six immune‐related genes (Tollip and ALF in haemocytes and hepatopancreas; lysozyme, crustin and cathepsin B in hepatopancreas; and LGBP in haemocytes) at 24 hpi after the three‐round challenge selection suggest that these immune parameters may be reliable markers for the evaluation of the physiological status and potential AHPND‐resistant phenotypes in E. carinicauda.