Susceptibility of freshwater fishes to barramundi nodavirus.
- There is a need to address concerns about the risk of possible lethal transmission of barramundi nodavirus to freshwater fishes already under threat in their natural habitat.
- Important freshwater fishes will be exposed to the nodavirus from cell cultures to determine their susceptibility.
- By using the OVL isolation facility in Townsville, well outside the Murray-Darling region, there is minimal risk to the natural fish populations.
- Confirmation that barramundi nodavirus can cause lethal infections in freshwater fishes will strengthen the application of strict licence conditions on barramundi farming in southern Australia.
- Confirmation that barramundi nodavirus does not affect freshwater fishes will possibly allow expansion of the barramundi farming into regions needing new sustainable economic development.
A barramundi infection model.
- To establish a realistic virus dose and route of infection for the challenge trials, an infection model using barramundi will be developed.
- OVL has ready access to barramundi larvae and fry of all ages.
- The model is also necessary to help quantify the effect of virus exposure to disinfectants and different environmental conditions.
What is the viability of barramundi nodavirus?
- Fish health management requires good information on how to effectively decontaminate facilities following outbreaks of VNN.
- Knowledge of the persistence of barramundi nodavirus in the environment will allow fisheries managers to decide on effective conditions for barramundi farming licences that minimise the risk of transferring virus outside the culture facility.
Sensitivity of the cell culture isolation system.
- While sensitive detection tests are available, the barramundi cell line offers a more practical diagnostic method that can be used by any laboratory with cell culture/ virology capability.
- An evaluation of the cell culture isolation system’s ability to detect virus in carrier (no disease) fish, and standardization of the cell culture presentation, is required before the method can be recommended.
Final report
This project has confirmed the knowledge that management of barramundi translocations outside their natural range requires fisheries authorities take into account the risk that barramundi nodavirus may lethally infect native freshwater fishes. The project has shown barramundi nodavirus can multiply and spread throughout the body of freshwater fishes, and that the spread of infection from fish to fish is a possibility in freshwater.
The project has created knowledge on the Australian application of a sensitive molecular detection test for nodavirus in healthy fishes. This knowledge has lead to industry and government support for further research on diagnostic test development for nodaviruses which will lead to a national Standard Diagnostic Procedure. Further, this knowledge has led the barramundi hatchery sector to support a research project applying the molecular detection test to screen captive barramundi breeders for nodavirus with the aim to produce nodavirus-free barramundi fry.
