The Australian authorities’ plan to introduce a virus to
control the carp population faces doubts.
Herd Immunity Could
Scarper Carp Control
BY JOHN DAWES
Carp are highly invasive. Everyone agrees. They can, and do, cause habitat deterioration, with serious consequences for native fauna and flora. Again,
everyone would agree. It is, therefore, highly desirable
to find a way of controlling or eliminating the species
from non-native waters, thus protecting autochthonous
wildlife. Yet again, no one would dispute this.
The challenge is: How do you go about doing this
in a way that satisfies all requirements, and without
causing new problems in place of the old ones? One
answer is to introduce a deadly disease-causing agent
that only affects carp, thus leaving all other species
unaffected. This, in fact, is the approach that the Australian authorities decided to adopt in 2016 to solve
the continent’s massive carp problem, but this is easier
said than done.
As I reported back in May 2016, if the idea had come
from our industry (because carp and koi are identical),
we would have been accused of “irresponsibility toward
the welfare of indigenous fish fauna, the environment
and, probably, much also besides.” However, while
the announcement that plans would be drawn up for
the release of the cyprinid herpesvirus 3 (CyHV3) virus
to reduce or eliminate exotic carp populations raised
concerns in many quarters—including the ornamental
aquatic sector—there was no huge public outcry against
To give the Australian authorities due credit, it was
never their intention to introduce the virus straight-
away without detailed investigation and consultation.
Mind you, if you listen to the Australian Deputy Prime
Minister/Minister for Agriculture and Water Resourc-
es, Barnaby Joyce, responding to a question regarding
the A$15 million carp-eradication program (this video
is really worth a look, I assure you!) in May 2016, you
could easily be led to think of the whole affair as a sick,
almost hilarious, joke, were it not for the seriousness of
the subject. Happily, not everyone within the Australian
corridors of power would refer to carp as “disgusting
mind-sucking creatures” worthy of a “venereal disease”
attack to eradicate them from Australian waters.
There is a host of other, very serious considerations
to be addressed, such as how to dispose of the countless
tons of dead carp, the adverse effect that these would
have on local, regional or even national water systems,
the huge costs involved in the removal of the corpses,
the risk of the virus being transferred to koi—with its
devastating consequences for Australia’s A$150 hobby
and trade sectors—the possibility of the virus mutating
into a form that could attack other species, like goldfish
… and so on.
To the best of my knowledge, none of these issues
have, as yet, been resolved. Now there’s another one to
consider, and this is a very significant one.
We know, for example, that the virus is not 100 per-
cent proof and that, while mortality rates are, undoubt-
edly, high, it could be around 70-90 percent. Of course,
this is high by any standard, but what happens with/
to the survivors?
According to associate professor Joy Becker of the
National Carp Control Programme Scientific Advisory
Group, her studies have led her and her team to con-
clude that the virus will not overcome the carp’s “re-
markable fecundity.” She goes on to say, “The release
of this herpesvirus in our waterways will undoubtedly
cause a single epidemic of herpesvirus disease resulting
in massive deaths among carp. … However, there’s little
evidence to suggest that we will see repeated outbreaks
of a magnitude to counter the reproductive potential of
the surviving carp.”
Becker and her colleagues believe that the likelihood
of the virus release controlling the continent’s carp pop-
ulation is significantly reduced due to what they refer to
as “herd immunity” and the species’ remarkable powers
of reproduction. They, therefore, conclude that the virus
release could end up being a one-hit wonder. Adding
further to the growing concern is the fact that, according
to the research team, the virus reaches a state of equi-
librium in host populations of carp within two years,
according to a study carried out in Japan.
So where does this leave the National Carp Control
Programme’s plan to release the CyHV3 virus into Australian waters? It’s too early to say as I write these lines,
but, if I were to hazard a guess, we won’t be seeing the
release taking place anytime soon.
Article from News Locker: newslocker.com/en-au/
Joy A. Becker, Michael P. Ward and Paul M. Hick. An
epidemiologic model of koi herpesvirus (KHV) biocon-
trol for carp in Australia, Australian Zoologist (online
ahead of print) doi.org/10.7882/AZ.2018.038.
Note: This link provides an abstract of the paper, which
was still awaiting publication at the time I prepared my report.
John Dawes is an international ornamental aquatic industry
consultant. He has written and/or edited more than 50 books
and has contributed more than 4,000 articles to hobby, trade
and academic publications. He is the editor of the OFI Journal
and a consultant to AquaRealm, the trade show that took place
June 2017 in Singapore.
Top: The release of cyprinid herpesvirus 3
(CyHV3) could end up as a one-hit wonder,
eradicating large quantities of carp, but not all.
Left: Koi (these are ghost koi) would be as affected as com-
mon carp, while goldfish (also in this photo) could become victims if
the virus were to mutate into another form.
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