Efficacy of double-stranded RNA for the large-scale control and prevention of sacbrood virus in Apis cerana (Hymenoptera: Apidae) apiaries

Sacbrood virus (SBV) infection in Apis cerana has caused tremendous damage in India, Thailand, Vietnam, and China since the 1970s. The disease caused by this virus results in colony collapse disorder in A. cerana and is also a devastating disease affecting A. cerana in South Korean apiaries. It has almost resulted in the elimination of the species. Therefore, control measures for this emerging threat are urgently needed. SBV RNA interference (RNAi) targeting VP1 was prepared to test the safety and efficacy of protection and treatment in artificially infected larvae and in infected colonies in South Korean apiaries. The efficacy of VP1 double-stranded RNA (dsRNA) was confirmed for the protection and treatment of infected larvae by increasing the survival rate in comparison with that in untreated larvae. Furthermore, an optimal application procedure was established for the large-scale RNAi treatment of SBV in apiaries. The protection of healthy colonies from SBV by RNAi was demonstrated in 100% of apiaries, and the treatment results showed that after five administrations, the SBV in infected colonies was mitigated to a safe level at which no symptoms of the disease were observed. Importantly, the low cost of dsRNA production in this study enables its application as a specific drug in large scale in South Korean apiculture.