It’s not a race, exactly, but there’s an intriguing uncertainty
about whether a former U.S. president or a software magnate will
cause the next deliberate extinction of a species in the wild.
Will Jimmy Carter eradicate Guinea worm
before Bill Gates eradicates polio?
It is more than a third of a century since a human disease was
extinguished. The last case of smallpox was in 1977, and in those
days health experts expected other diseases to follow smallpox
quickly into oblivion. Polio has repeatedly disappointed campaigners by
hanging on, though it now affects less than 1% as many people as at
its peak in the 1950s.
The generosity of Bill Gates has done much to speed the decline
of polio, and he and most experts now see its end within six years
at most. India, 10 years ago the worst-affected country, has been
polio-free since 2011, and only three countries still host the
virus: Pakistan, Afghanistan and especially Nigeria. Though the
murder of nine polio vaccinators in Pakistan by Islamists in
December was a tragic setback, last year there were just 222 new
polio cases world-wide.
As Mr. Gates recounted in his 2013 annual letter from the
Gates Foundation, the reason for his optimism is that a new
approach is bearing fruit, especially in northern Nigeria.
Volunteers on foot (but guided by GPS and satellite imagery) map
unrecorded villages and houses to identify gaps in vaccination
The Guinea worm, a disease that the Carter Center has relentlessly pursued, will probably edge
out polio to the disease extinction line. In 1986, more than 3.5
million Africans and Asians were afflicted with Guinea worm, or
dracunculiasis; in 2012, just 542 caught the parasite.
The larvae of this nematode worm live inside freshwater
copepods, or “water fleas.” When the copepods are ingested in
drinking water, the worms burrow through the stomach wall into the
body cavity and mate. The females, which can reach 3 feet in
length, then drill their way down the inside of the victim’s legs
over a year before erupting painfully from a burning blister on the
foot. The victim is tempted to immerse the blister in water to cool
it, which allows the worm to release its larvae to seek copepods.
The only cure is to pull the worm out over many weeks, inch by
inch, winding it round a stick as it emerges. There is no
Filtering water to prevent the ingestion of water fleas and
making sure infected people do not enter water are the best means
of prevention. Guinea worm was first targeted for eradication
before polio, and it, too, has been disappointingly stubborn. But
last year the number of cases halved from the year before, meaning
that there are fewer guinea worms left in the world than black
rhinos. The handful of cases in Chad (10), Mali (7) and Ethiopia
(4) are expected to dwindle to nothing this year, but there were
521 cases in South Sudan (mostly in just one county), where
eradication might take one or two more years of hard work, urged on
by Mr. Carter and backed by money from the Gates Foundation, the
British government and other donors. Guinea worm would be the first
animal to be deliberately driven extinct.
Supposing these two welcome eradications do happen this decade,
what parasites go next? Don Hopkins of the Carter Center says
lymphatic filariasis, another worm carried by mosquitoes, could be
gone by 2020. Onchocerciasis, or river blindness, carried by black
flies, is almost gone from the Americas but will take longer to
eradicate in Africa.
The first bacterium to be driven extinct could be yaws, an infection of children
related to the organism that causes syphilis, which disfigures many
people, especially in Ghana, Ivory Coast, Papua New Guinea and the
Solomon Islands. Easily treated now with a single dose of
azithromycin, an antibiotic, yaws should be gone by 2020.