Clearance of Penaeus monodon densovirus in naturally pre-infected shrimp by combined ns1 and vp dsRNAs

Penaeus monodon densovirus (PmDNV) is one of the major causes of stunted shrimp in Thailand and leads to considerable economic losses in overall shrimp production. Present study shows that the double-stranded RNA corresponding to the non-structural protein gene (ns1) and structural protein gene (vp) of PmDNV effectively inhibit viral propagation in naturally pre-infected shrimp. Multiple application of dsRNA was performed by injection into the haemolymph. The total amount of virus in the hepatopancreas of treated shrimp was measured by semi-quantitative PCR and histological methods. Observations indicated that PmDNV was almost eradicated in comparison to the high viral propagation in the control groups (no dsRNA and non-related dsRNA-gfp). For heavily infected shrimp, simultaneously knock down of ns1 and vp genes exhibited greater potency for viral depletion than dsRNA-ns1 alone. Furthermore, typical hypertrophic nuclei were also reduced in treated shrimp. This study therefore demonstrates the first result of an effective anti-PmDNV therapy in naturally pre-infected shrimp.