RNA interference-based oral therapeutant for White Spot Syndrome Virus in shrimp

Aquaculture is the fastest growing animal food-producing sector and has been projected to play a very important role in meeting the food demand of the growing world population. Shrimp is the most important aquaculture commodity accounting for nearly twenty percent of the total value of international trade of fish products. However, as with other aquaculture species, shrimp aquaculture suffers significant losses (about 15 to 30 percent) annually due to disease outbreaks. White Spot disease (WSD), caused by the White Spot Syndrome Virus (WSSV), has been the most problematic viral pathogen affecting global shrimp farming since emerging in 1992. It is one of the most widespread viruses in the industry, occurring in virtually all shrimp farming countries. Over 50 crustacean species have been found to be susceptible to WSSV, including crayfish, crabs, lobsters, etc., which also act as carriers of the virus. It is highly virulent and may result in 80-100 percent mortality in ponds within 7-10 days of infection. Such extreme losses affect food security and cause profound socio-economic distress. Various strategies have been tried to control WSSV infection in shrimp - all with mixed results. In addition, various preventive strategies such as use of pathogen free shrimp larvae, application of bio-secure farming/aquaculture techniques, disinfection and use of WSSV resistant strains are commonly adopted to reduce the appearance of the pathogen. However, these strategies do not provide an effective protection once the viral infection appears in a shrimp farm. Currently, no viable commercial product exists to combat WSSV in shrimp. There is a clear and immediate need to develop a novel therapeutant and delivery method that can provide effective protection against WSSV in shrimp. RNA interference (RNAi) is a process within living cells that moderates the activity of their genes. RNAi based strategies appear to be promising in controlling WSSV in shrimp. Preliminary data suggest strongly that our RNAi strategy which targets four WSSV genes may provide very potent protection to shrimp against WSSV. In collaboration with an independent industry leading third party laboratory, an injection trial was conducted on juvenile shrimp, the results of which confirmed strongly the efficacy of our RNAi strategy in providing protection to shrimp against WSSV. It is anticipated that the work proposed in this project will produce new fundamental and applied knowledge that will be shared via collaboration, publications, conferences and word-of-mouth. Success in this project will catalyze action to commercialize a much needed product and validate methods to control viral disease that could open up a new area for improved disease control in animal husbandry. This project proposes the development of an RNAi-based therapeutant against WSSV of shrimp delivered orally through microalgae/yeast consumed by the shrimp.