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Carp virus updates
Two carp photographed under artificial light in an aquarium
The fish of concern.
Source: Rudi Kuiter

In 2023, a new round of questioning began in regard to the status of the Cyprinid herpesvirus-3 (carp virus).

click here to learn ‘what’s the go with the carp virus?’

Every few years this topic hits the mainstream media and causes a lot of confusion, debate and controversy. In May I was able to attend an online webinar hosted by the Department of Agriculture, Fisheries and Forestry all about the next phase for carp biocontrol. The webinar was facilitated by Australia Chief Environmental Biosecurity Officer, Dr Bertie Hennecke, and featured Toby Piddocke from the Fisheries Research and Development Corporation (FRDC).

Recent updates

The National Carp Control Plan (NCCP) is still in the research phase. This phase is the largest feasibility assessment of a biological control agent undertaken in Australia. The research covers 19 different projects involving 11 national and international research institutions and over 40 research scientists. The different search projects can be grouped under four main categories:

  • Understanding carp virus effectiveness
  • Understanding risk
  • Managing risk
  • Benefits and costs

The invasive carp out-competes native fish species in habitat that has been modified. Source: Arthur Rylah Institute.

The program is entering ‘NCCP Phase 2′, which begins with prioritising the above research actions. The vital parts of this phase include; priority research actions (field trial planning), Minister’ agreement to proceed, public stakeholder consultation, legislative and regulatory approvals and finally a decision point on whether to release the virus

So, what now?

The current headline messages arising from the virus research include:

  • 40-80% reductions in carp numbers possible (dependant on demography)
  • Initial major outbreaks followed by ongoing seasonal kills of mainly small carp
  • Suppression through “boom” cycles
  • A “carpageddon” is rather unlikely, rather; a concerted effort to introduce the virus and initiate outbreaks in targeted carp populations
  • Water quality risks are less than if the virus was self-propagating, but considerable effort likely needed for broadscale rollout and risk management will require broadscale surveillance.
  • Broadscale water quality impacts unlikely, but could occur in some habitat types.

A hand holds a carp out of the water in dappled light - out-of-focus greenery is visible in the background.
Carp (Cyprinus carpio). Photo credit: Queensland Government

Something to clarify…

One of the biggest concerns to the public regarding the release of this virus is the susceptibility of non-target species (NTS). The World Organisation for Animal Health (WOAH/OIE) lists carp and carp-hybrids as the only species filling its criteria as susceptible to Cyprinid herpesvirus-3 infection. However, detection of the virus has been found in genomic DNA in several other freshwater fishes and invertebrates – this doesn’t necessarily mean they are infected. The main challenges and uncertainties remain, hoping to be addressed in the ongoing research. The project is earmarked by a variety of stop-go decision points as the research progresses:

Priority research actions NCCP 2024. Source: Department of Agriculture Fisheries and Forestry (DAFF)

Two other key concerns involve risks to the wider ecosystem (ie. water quality) and development of genetic resistance (ie. developed immunity).

A classic example of this is the biological control of rabbits using Myxoma virus in 1950 and the Rabbit Calicivirus in 1995. Both the virus and rabbits are constantly evolving, meaning that changes in virus severity and genetic resistance in rabbits means that numbers are slowly climbing again. However, biological control is by far the most nationally cost-effective control option for rabbits and keeping their numbers down is vital for industry.

It is important to go slowly with the carp virus as adequate research is a crucial element to any kind of biocontrol, particularly around the risks to NTS.

For now, all we can do is wait and see how the carp virus research progresses!

Watch the full webinar here on the Department of Agriculture, Fisheries and Forestry’s webpage here.

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