A new method for quantifying white spot syndrome virus: Experimental challenge dose using TaqMan real-time PCR assay

White spot syndrome virus (WSSV) is an important pathogen in shrimp aquaculture. The susceptibility of crayfish (Procambarus clarkii) was assessed by means of serial dilutions of a solution containing WSSV. A TaqMan real-time PCR was used to quantify the WSSV challenge dose in P. clarkii. The results showed that WSSV copies could be detected at concentrations from 1.365 × 104 to 1.129 × 109 copies/μl. The viral infectivity (LD50), measured as the mortality of infected crayfish, indicated 60% mortality in the 105 dilution group (1.524 × 105 copies/μl). TaqMan real-time PCR represents a novel standard method, based on the by quantitation of WSSV copies, for determining the appropriate concentration of WSSV for use in infection experiments.

► The precise challenge dose of WSSV was identified firstly by TaqMan real-time PCR.
► WSSV copies were detected from 1.365 × 104 to 1.129 × 109 copies/μl in serial WSSV dilutions.
► The result showed the LD50 was about 105 dilution and WSSV copies was 1.524 × 105 copies/μl.