1. RNAi treatment of broodstock to reduce disease impacts in farmed prawns Melony Sellars Jeff Cowley, Min Rao, Brian Murphy, Dean Musson
Aquaculture Program - CSIRO Agriculture and food flagship

2. Knowledge to-date for prawns & RNAi
RNAi antivirals reduce viral loading of Penaeid prawns through tail muscle injection
of all commercially relevant viruses in juveniles under laboratory conditions
of broodstock Black Tiger females from GAV under commercially comparable conditions
Antivirals and the administration process do not adversely impact the ability of female Black Tiger prawns to spawn
Injection is the only reliable administration method at present

3. The challenge for our industry
GAV is endemic in Black Tiger prawns indigenous to coastal waters and it’s not uncommon for wild broodstock used in hatcheries to be infected with GAV at high prevalence
GAV is transmitted vertically from broodstock to progeny very effectively
GAV infections carried into ponds with seedsock are a primary contributor to ‘disease-related’ production losses during grow-out

4. Potential solutions to this challenge
Source broodstock from elsewhere
Expensive to collect broodstock from remote locations
Potential for introducing new pathogens (FRDC Project 2013/036)
Viability of local commercial broodstock suppliers
Undertake PCR-based screening selection for GAV-free or GAV-low broodstock
Expensive, labour intensive and requires laboratory support
Not practical when infection prevalence and loads are high
Stimulate the RNAi pathway to reduce or clear GAV infections by injecting broodstock with GAV-specific dsRNA
Grow-out of progeny from cleared parents and assessment of progeny performance – now underway
Registration requirements - Australian Pesticides and Veterinary Medicines Authority (APVMA)
Establish virus-free or disease-resistant breeding populations

5. Potential solutions to this challenge
Source broodstock from elsewhere
Expensive to collect broodstock from remote locations
Potential for introducing new pathogens (FRDC Project 2013/036)
Viability of local commercial broodstock suppliers
Undertake PCR-based screening selection for GAV-free or GAV-low broodstock
Expensive, labour intensive and requires laboratory support
Not practical when infection prevalence and loads are high
Stimulate the RNAi pathway to reduce or clear GAV infections by injecting broodstock with GAV-specific dsRNA
Grow-out of progeny from cleared parents and assessment of progeny performance – now underway
Registration requirements - Australian Pesticides and Veterinary Medicines Authority (APVMA)
Establish virus-free or disease-resistant breeding populations

6. Project goals
Demonstrate dsRNA antivirals can abrogate or reduce vertical transmission of GAV to progeny
Quantify improvements in health, survival and growth performance of progeny that are spawned from GAV infected parents that receive the antiviral compared to progeny from GAV infected parents that do not receive the antiviral
Deliver proof-of-concept that antivirals can be up-scaled for use in commercial hatcheries and result in progeny with lowered viral infection loads that realise commercial benefits in prawn health, growth and survival

7. Experimental workflow 2016-2017
Reproductive performance data
Growth and survival performance data
GAV load broodstock
GAV load broodstock
GAV load broodstock
GAV load female spawner
GAV load emrbyos
GAV load PL15
GAV load PL60
GAV load PL100
GAV load PL140
GAV load PL180
11July
29July
15Aug
20Aug
20Sept
Feb/Mar
Destination
GAV antivirals that reduce vertical transmission
Ablate & inject antiviral or saline
Spawning
10 treatment families
10 control families
Source broodstock from Qld EC
GAV PCR screen
Inject antiviral or saline
Harvest ponds once marketable size
Stock 2 treatment, 2 control ponds

8. Thankyou
This research is supported by the Australian Prawn Farmers Association, Fisheries Research and Development Corporation, Science and Industry Endowment Fund and CSIRO