Monitoring the secreted profile of PirAvp and PirBvp toxins from Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease

The lethal PirAvp and PirBvp toxins from Vibrio parahaemolyticus are responsible for acute hepatopancreatic necrosis disease (VPAHPND) in shrimp. After causing infection in the stomach of shrimp, VPAHPND released PirAvp and PirBvp toxins into the culture medium and lead to massive sloughing of cells. These effects resulted in high mortality rate during the first 35 days after culture. However, there have not been many studies on the amount of these toxins in the culture process over time. Thus, in the present study, we use lateral flow immunoassay (LFIA) strip and ELISA to screen the concentration of pathogenic bacteria in cultured medium over time to detect the disease early. The results showed that ELISA was able to detect PirAvp and PirBvp levels at 0.043 and 0.020 μg/ml, respectively. After incubation, bacteria secrete both PirAvp and PirBvp toxins equally, but after 12 h, the secretion of PirBvp increased three times more than PirAvp. Verifying with LFIA strip showed that test strip was able to detect clearly PirAvp and PirBvp at 3 h and 107 CFU/ml. After each point time, the detectable LFIA signal increased by one dilution order. This result indicated that PirAvp and PirBvp toxins were secreted over time, which help to study the role of these toxins in the pathogenic process. Furthermore, LFIA strip can be used for early detection of AHPND to help reduce economic losses for shrimp farmers.