Quantitation of infectious myonecrosis virus in different tissues of naturally infected Pacific white shrimp, Litopenaeus vannamei, using real-time PCR with SYBR Green chemistry

The Pacific white shrimp, Litopenaeus vannamei, is the most important shrimp species in volume in world aquaculture. However, in recent decades, outbreaks of diseases, especially viral diseases, have led to significant economic losses, threatening the sustainability of shrimp farming worldwide. In 2004, Brazilian shrimp farming was seriously affected by a new disease caused by the Infectious myonecrosis virus (IMNV). Thus, disease control based on rapid and sensitive pathogen detection methods has become a priority. In this study, a specific quantitation method for IMNV was developed using real-time PCR with SYBR Green chemistry and viral load of the principal target tissues of chronically infected animals was quantified. The quantitative analysis revealed that mean viral load ranged from 5.08 × 10⁸ to 1.33 × 10⁶ copies/μg of total RNA in the hemolymph, 5.096 × 10⁵ to 1.26 × 10³ copies/μg in the pleopods, 6.85 × 10⁸ to 3.09 × 10⁴ copies/μg in muscle and 8.15 × 10⁶ to 3.90 × 10³ copies/μg in gills. Different viral loads of IMNV were found with greater values in the hemolymph and muscle, followed by the pleopods and gills.