Sometimes it is right to wipe out a species

My Times column is on the eradication of diseases
and the resurrection fo extinct species. Both interferences with
nature would be a good thing.

The World Health Organisation’s annual assembly
decided on Saturday evening not to set a date to destroy the last
two remaining samples of smallpox virus kept in secure laboratories
in Atlanta and Novosibirsk. Smallpox, being a virus, does not
really count as a living species. But the prospect of the
deliberate extinction of some harmful species is getting closer. Be
in no doubt — it would be an unambiguously good thing.

Smallpox was eradicated outside laboratories in 1977, when Ali
Maow Maalin recovered from the disease in Merca, Somalia (he died
last year of malaria). Until now researchers have wanted to keep
the virus alive in the laboratory just in case they need to study
it further. Pretty well everybody now agrees that the risk of
keeping the virus is greater than the risk of not keeping it.
Remember that the last case of smallpox was the death of Janet
Parker, a medical photographer, in Birmingham in 1978, who caught
it from a laboratory.

Last year the WHO convened a group of independent experts who concluded that “there is no need, from a global
public health perspective, to retain live Variola
virus [its scientific name] for any further research”. They also
pointed out that 600 million doses of smallpox vaccine remain
available in the highly unlikely event that — say — a live virus
emerges from a buried corpse in the frozen tundra.

If you had predicted in 1978 that 36 years later we would have
extinguished no more diseases (apart from rinderpest, a cattle
disease), you would have been thought a dire pessimist. Yet
smallpox turned out to be uniquely vulnerable to eradication
because its short incubation period, lack of an animal reservoir
and its obvious symptoms allowed rapid vaccination responses to
contain outbreaks. Polio was expected to follow it to the viral
grave soon afterwards, but that dream has been repeatedly
postponed.

Indeed, this year polio is resurgent, with 82 cases so far, compared
with 34 by this date last year. Most of them are in Pakistan, a
country where polio vaccinators are sometimes murdered by the
Taliban on the suspicion that they are US or Israeli agents
spreading Aids or sterilising girls.

Disastrously the CIA helped to give credence to such rumours by
using a local doctor to run a hepatitis
vaccination project as cover for trying to get blood samples from
the children living at Osama bin Laden’s compound in Abbottabad, in
order to identify who was living there. The doctor is now in
jail.

There is even a brief glimpse in the film Zero Dark
Thirty of a fake vaccinator, wearing a jacket with “Polio”
written on the back, trying to get access to the house — a factual
mistake by the film makers that can only have
exacerbated the risk to real polio vaccinators. Last week the Obama
administration promised the deans of 12 public health schools
that it would never use fake vaccinators again, but that promise
comes too late for those paralysed by polio in Pakistan in the past
few years.

The imminent eradication of the guinea worm in Africa has also
suffered a setback this year. Last month there were just three new cases, down from 25 in
April last year and 80 in April 2012. But one of them was in Chad,
where a handful of recent cases have occurred in people and dogs
near the Chari river, an area previously thought to be free of the
problem. The others are in South Sudan, where, despite the war, the
parasite does seem to be coming under control.

Is such deliberate extinction of creatures that cause suffering
a good idea? As long as the effect on ecosystems is small, then the
answer is clearly yes. Take mosquitoes, for example. There are
2,500 species of mosquito in the world and only one of them
— Aedes aegypti — is responsible for carrying
dengue fever, a disease that currently afflicts nearly 400 million
people and rising. If you were to wave a magic wand and get rid
of A aegypti, then there would be plenty of other
mosquitoes to take its place in ponds and puddles.

And waving such a magic wand is no longer completely
implausible. Last month the Brazilian government gave an Oxford-based company called Oxitec a
licence to release into the wild genetically engineered
male A aegypti mosquitoes. They carry two extra
genes that render their offspring incapable of breeding. Release
enough of them in an area and the species all but dies out locally.
The beauty of this scheme is that the rarer the species gets, the
better the chance that the genetically engineered males you release
will mate with any available females, so the technique becomes more
effective, not less, as local extinction approaches.

Global eradication of even this one species of mosquito is
likely to remain practically impossible, but local extinction might
well be feasible. And, although it is not the insect’s fault that
it carries the dengue virus, good riddance. The ecological impact
of reducing the diversity of mosquito fauna by one species will be
undetectable.

As the prospect of eradicating species we dislike gets closer,
so the prospect of resurrecting extinct species we like gets closer
too. Exactly a century ago this September the last living specimen
of the passenger pigeon, a female called Martha, died in Cincinnati
zoo. The DNA sequence of the passenger pigeon has now been read,
and a researcher named Ben Novak is beginning to put together a
plan for how to edit the chromosomes of a closely related species,
the band-tailed pigeon, until they match the passenger pigeon’s.
After that, a cell with the edited genome could be turned into an
embryo and grown in an egg. (Full disclosure: I am an adviser to
the project.)

Some nattering nabobs of negativism are worried that this is a
bad idea. It might risk upsetting today’s ecologies or make us
complacent about extinction. Worse, argues one critic, it is “a refusal to accept
our moral and technological limits in nature”. Yup. That refusal is
something I am eternally grateful for, as a person who was
vaccinated against smallpox.

Imagine, 50 years from now, that we have resurrected five
species — the passenger pigeon, mammoth, dodo, thylacine and great
auk — but eradicated five others: the guinea worm, dengue mosquito,
leprosy bacillus, malaria parasite and river-blindness worm. Would
that be a better world? Yes.