The National Carp Control Plan (NCCP), an initiative of the Australian government, aims to reduce common carp numbers in Australian waters. A key aspect of this plan is to use a biological control agent to kill common carp in waters of the Murray-Darling basin. Since 2008 CSIRO researchers have been investigating the potential for Cyprinid herpesvirus 3 (CyHV-3) to control common carp numbers in this region as well as exploring potential negative outcomes arising from the introduction of this exotic virus. One critical issue is the potential for non-target species (NTS) to be infected and negatively affected by CyHV-3.
Susceptibility studies performed in vitro and in vivo were undertaken and used to predict in situ outcomes. These studies indicated that NTS tested were not susceptible to CyHV-3. However, since the publication of these results, stakeholder groups have raised several concerns. These concerns must be resolved to mitigate against the infection of NTS by CyHV-3 and to ensure continued stakeholder engagement. Six areas of concern have been raised by stakeholders.
1. Immune-competency status of fish was not considered in susceptibility studies
2. Techniques used to determine viral infection were perceived to be unreliable
3. Undiagnosed mortalities of NTS were not adequately addressed
4. Positive PCR test results observed in NTS were not adequately explained
5. Only mature or advanced juvenile fish were assessed for susceptibility to CyHV-3
6. The range of NTS investigated for susceptibility was limited and did not include a number of species that may be exposed to CyHV-3
It is proposed that a discussion paper be prepared to examine these issues. This paper would determine if previous susceptibility testing for CyHV-3 in the NCCP adequately addressed those issues detailed above. Using the information collected, recommendations for susceptibility testing of NTS to CyHV-3 in the context of the NCCP would be presented. The current understanding of what constitutes best practice for viral susceptibility testing at the time of the review would also be discussed. This would include a commentary on the predictive capacity of in vitro and in vivo studies when translated to the in situ environment.