There are a couple of articles on CAARRRP herpes doing the rounds that answer a lot of the questions and concerns some people have had:
https://theconversation.com/carpageddon ... alia-58787
Yesterday’s announcement of funding for a National Carp Control Plan – including the release of the carp herpes virus – has generated a lot of interest in the media. I welcome plans to release the virus by the end of 2018. In January I wrote an article here explaining the concept and why I think it could work in Australia.
Since the announcement I’ve listened to discussions on radio and television highlighting the concerns of the public. I hope to address some of the confusion and set the record straight.
What will we do with piles of dead fish?
Among people who live near the Murray River or one of its tributaries, this is the main objection to the release of the virus. This in itself suggests that those close to the rivers understand the implications of carp being 80% of the biomass in the Murray Darling Basin. Many people have lived through black-water events (where oxygen levels drop resulting in large fish kills) and they know how unpleasant it is to have a lot of dead fish at one time.
Their concerns are justified. Fortunately, Science Minister Christopher Pyne is aware that hundreds of thousands, possibly millions of tonnes of dead carp will need to be cleaned up, and this will require community consultation and potential legislative changes. Pyne says we can use dead carp as fertiliser, as pet food or bury them in large graves. It is interesting to note that the fertiliser company Charlie Carp welcomes the move and may expand their business into South Australia so they can respond to large fish kills there.
The trick will be disposing of the fish quickly because after 48 hours they will begin to rot and will not be suitable for use. My reading of the announcement suggests that planning for this one time big carp kill will be a large part of the $15 million spent over the next two years.
How is the virus transmitted?
There were some giggles about how this virus is transmitted among fish, given that herpes is a sexually transmitted disease in humans. However, all the fish have to do is bump into one another to transmit the virus, and they can also be infected by the virus that lives in the water, although the virus will only survive for a few days outside of the body of a fish.
Once infected, any survivors will carry the carp-specific herpes virus for life. Stress can re-activate the virus, causing it to persist in the carp population and allowing it to spread rapidly under crowded conditions.
What a waste – we could have sold these fish overseas!
It is true that Australians resist eating carp due a perception that they are “junk” fish. Some say they have a muddy flavour, or that they are too bony. Neither of these issues stop people in Europe, the Middle East and Asia eating carp, where they are a common part of the diet.
There are two problems with the suggestion that we are missing a commercial opportunity here. The first is the economic viability of shipping fish to the other side of the world. We cannot get them there alive so we will need to freeze or can the carp, and once we’ve done that, consumers must pay enough to cover the processing and shipping.
I was on a committee with the NSW Department of Fisheries 15 years ago that was looking for markets for carp products. Enthusiastic investors with support from government could not find a way to make money with this export.
The second problem is that any industry relying on carp as a product will not remove carp from our rivers. Carp are causing enormous damage to the ecology of rivers and lakes across our continent and fishing alone will never remove enough of them to return those ecosystems to health.
But biological control never works, does it?
“Myxomatosis and cane toads – need I say more?” was a text to my local ABC radio station by someone concerned about the failure of biological control in the past. Yes, cane toads were a disastrous introduction to Australia and it is now clear that the problem was insufficient research prior to release. The carp herpes virus has been researched in Australian laboratories for 7 years so far. See my previous article for more on why this looks like a safe bio-control option.
Myxomatosis actually worked beautifully, killing 500 million rabbits in two years after the first release in 1950. Resistance did increase in the decades to follow and in 1996 another virus (calicivirus) was released to further reduce rabbit populations.
The rabbit plague of 1860 onward was the fastest spread of any mammal in the world. Rabbits had an enormous environmental and economic impact right across Australia, leading us to build the rabbit-proof fence. In 1887 the state of New South Wales was offering a reward of £25,000 for any successful method not previously known for exterminating rabbits. Although srabbits were useful for food in the depression and to make lots of hats, nobody wants to return to pre-myxomatosis times.
And no, we didn’t kill all the rabbits, just like we will not kill all the carp. However, a virus transmitted by water may be more effective as suggested by the government’s goal of a 95% carp reduction by 2045.
Carp are natural by now – our native fish rely on them for food
Australian native fish have been seriously impacted by carp. Many of them are visual predators, such as the magnificent Murray Cod. The turbidity created by carp reduces their ability to hunt and thrive, even though the high biomass of carp may give them plenty to eat.
The muddy river that runs through my home town is a hazard for swimmers and boaters because you can’t see the snags. This is due almost entirely to the presence of carp. None of us can remember when the Murray River ran clear and native fish were more common than introduced fish, but Senator Anne Ruston, Assistant Minister for Water Resources, recalls her mother and grandmother talking about being able to see the bottom of the river.
If you cannot imagine why anybody cares what type of fish are living in our rivers, remember that native Australian fish and plants are not adapted to the muddy rivers we have now. Let’s give them a chance to grow and thrive again in an environment more similar to the natural situation.
Sounds like a waste of money
Our Deputy Prime Minister Barnaby Joyce says that carp cost the economy up to $500 million per year. I don’t know how he got that figure but it may include the extra water treatment we need for river towns like mine and tourism losses due to reduced biodiversity and frequent algal blooms. Even if it is only half of that, spending $15 million to remove carp from the system seems like a sound investment.
The future of Australia’s waterways are at stake. Is there anything more precious than clean, fresh water?
and this one which I won't quote in full because it's pretty long
https://blog.csiro.au/reclaiming-our-ri ... eral-carp/
2. Will CyHV-3 be effective as a biocontrol agent?
CyHV-3 first appeared in Israel in 1998 and quickly spread throughout the world, killing-off common and koi carp. Ironically carp are farmed in many countries and are an important food source. So, while CyHV-3 has devastated carp farming, the overseas experience has demonstrated how it could be used successfully as a biocontrol agent here.
Testing of CyHV-3 in the high-security Fish Diseases Laboratory at our Australian Animal Health Laboratory (AAHL), in Geelong, Victoria, has proven that the same virus does in fact kill Australian carp, and it kills them fast.
The flip side is our rigorous testing to ensure that the virus won’t affect native Australian or important introduced species of fish. It has been shown to pose no danger to 13 native species such as Murray cod, various species of perch, eel and catfish, as well as a crustacean (yabbies) and a non-native fish species, the rainbow trout. Our work has shown that there are no clinical or pathological changes in these non-target animals, nor is there any evidence that the virus multiplies in these species.
Chickens, mice, frogs, turtles and water dragons have also been tested as representatives of a wider community of birds, mammals, amphibians and reptiles. Again the virus has shown no effect on them which also makes us confident that it won’t affect that other major group of mammals – humans.
Based on lessons learnt from past use of viral biocontrol agents for invasive vertebrates, we expect that CyHV-3 will have the greatest impact in the first couple of years after release. After that, its effectiveness may be diminished, but not lost, as virus and host adapt to each other.
Therefore, we need an integrated pest management program that utilizes other methods to complement our virus. These include new broad-scale technologies such as ‘daughterless’ technology to create male-only populations, as well as traditional regional methods such as trapping, the commercial collection of carp, and controlling access of carp to breeding grounds.
4. How can we be sure that widespread distribution of the virus is safe for people?
CyHV-3 has devastated carp farming around the world yet despite the large numbers of people working on these affected farms, there has been no evidence of any effect of the virus on them.
We have also exposed mice to CyHV-3, and found no evidence of disease. Mice were chosen as being a representative mammal, just like a human.
And finally, a report to the European Commission by the Scientific Committee on Animal Health and Animal Welfare stated that there is no evidence for ANY fish virus causing disease in humans.
How does the herpes virus work?
The virus – CyHV-3 – mainly damages the kidneys, skin and gills of koi carp. Kidney and skin are very important in helping the fish maintain its water balance. Animals living in a freshwater environment need to stop water getting into the body (skin) and to pump out excess water that does get in (kidneys). In affected fish there is a water imbalance which causes a mineral imbalance. Among other things, the latter could affect heart function (although that has not yet been shown in carp). Damage to the gills affects the carp’s ability to breathe and this is the cause of death.
After a fish is infected by the virus, the virus multiplies in the fish for about seven days (depending on the water temperature). During this time the fish eats and appears quite normal. It then takes about 24 hours from the first signs of disease (darkening of the skin; reddened gills) until the fish dies.
How is it transmitted?
Most commonly the virus appears to be transmitted by direct contact between fish, but fish can also be infected by virus in the water. The virus alone will never wipe out carp completely; there will always be some survivors. As in ANY herpesvirus infection in any host, survivors are infected with herpesvirus for life. These are what is known as latent infections, where the virus is present but does not seem to cause any signs of disease. However, if a latently-infected animal is stressed for any reason then the virus re-activates and can be spread. This should allow the virus to survive in the carp population.
How do you know it won’t infect other species?
We have done rigorous testing to ensure that the virus won’t affect native Australian or important introduced species of fish. It has been shown to pose no danger to 13 native species such as Murray cod, various species of perch, eel and catfish, as well as a crustacean (yabbies) and a non-native fish species, the rainbow trout. Our work has shown that there are no clinical or pathological changes in these non-target animals, nor is there any evidence that the virus multiplies in these species.
Chickens, mice, frogs, turtles and water dragons have also been tested as representatives of a wider community of birds, mammals, amphibians and reptiles. Again the virus has shown no effect on them which also makes us confident that it won’t affect that other major group of mammals – humans.
What’s to stop the virus mutating and infecting other species?
When it comes to understanding the effects of mutations in viruses, work on many viruses over many years has resulted in some general observations. Firstly, some viruses are naturally promiscuous, meaning they will infect a wide range of species (e.g. the influenza viruses). Herpesviruses are NOT considered to belong to this promiscuous group of viruses. In fact, herpesviruses are generally considered to be species-specific, i.e. each host species has its own herpesvirus(es). Secondly, viruses that are species-specific can occasionally jump into new hosts, but these jumps seem to be determined by two factors.
The vast majority of virus jumps really only occur between closely-related host species (e.g. AIDS virus and Ebola virus jumping from non-human primates into humans).
The nature of the genetic material of the virus. Viruses can be broadly classified as RNA or DNA viruses depending on the nature of their genetic material. DNA viruses (like koi herpesvirus) are relatively stable, whereas RNA viruses (like AIDS virus, Ebola virus, influenza virus) are much more likely to undergo mutations that potentially allow these viruses to jump hosts (although, as already mentioned, generally the jump is still into a closely-related species). In comparison, koi herpesvirus is a very large and complex DNA virus, and as a result they are rarely associated with jumps.
It’s worth noting that two viruses have been released in Australia to control rabbits, the Calicivirus (an RNA virus) and before that, the virus causing Myxomatosis (a complex DNA virus). These viruses have been present in Australia for around 20 and 60 years respectively and there is still no evidence of either virus jumping into another host during all that time.
For koi herpesvirus, the important observation is that it has only been found in carp. Carp belong to a group of fish known as cyprinids, and there are no native cyprinids in Australian waterways. The native fish in Australia that are most closely related to cyprinids are the native catfish. The susceptibility of two different species of native catfish to koi herpesvirus has been tested, and there was no evidence of disease or of virus multiplication in either species.
Won’t carp eventually develop resistance to the virus?
Whenever a virus is used as a biocontrol agent, the virus kills large numbers of the target for the first couple of years. But, gradually the virus and host come to a state of equilibrium that allows both to survive. At that point there has been a marked initial reduction in the numbers of the target, and the virus then continues to cause a lower level mortality in the target such that the target numbers never recover to their original levels.
We’ve seen this happen with both the Calicivirus and the Myxoma virus in their effects on rabbits, and those viruses still do a great job in controlling rabbit numbers in Australia.