Malaria experts
have been holding their breath and hoping it wouldn't happen. But it has.
Malaria parasites resistant to the last, best drug treatment, called
artemisinin combination therapy, or ACT, are infecting people along the border
of Thailand and Myanmar.
This is 500 miles away from the first focus of ACT-resistant malaria in
Cambodia. And it's a different form of resistant malaria, which means it arose
independently of the Cambodian type rather than spreading from there. We're
talking here about Plasmodium falciparum, the deadliest and most common form of
malaria.
The discovery ruins the World Health Organization's hope that
resistance to ACT might be stamped out for good in Cambodia. Now it's a
two-front war.
An international team of researchers is publishing the news in The
Lancet.
Meanwhile, many of the same scientists report in Science that they've
zeroed in on changes in the parasite's genes that drive this new form of
resistance. That gives hope that its spread may be monitored and that new drugs
might someday be devised to foil resistance.
But the bad news outweighs the good. The new resistance raises concern
that the tantalizing prospect of eliminating malaria might slip away again, as
it did when the parasite developed resistance to the drug chloroquine in the
1960s through the 1990s. More than 600,000 people die of malaria each year, but
the toll has been falling.
Artemisinin-based therapies are a big reason why the hope of
eliminating malaria has been rising. Other reasons are wide distribution of
insecticide-treated bed nets to prevent mosquitoes from transmitting the
parasite at night, and last fall's announcement that the first large field
trial of a malaria vaccine reduced infections by 55 percent.
"Anti-malarial control efforts are vitally dependent on
artemisinin combination treatments," write Anne-Catrin Uhlemann and David
Fidock of Columbia University in a Lancet editorial. "Should these
regimens fail, no other drugs are ready for deployment, and drug development
efforts are not expected to yield new anti-malarials until the end of this
decade."
Thus, the new focus of resistant malaria is likely to stimulate urgent
strategy sessions about whether it can be contained, as authorities still hope
the Cambodian outbreak might be.
Working against that is the fact that the new resistance involves
Myanmar, which has a lot of malaria and a weak public health system.
Researchers say that ACT regimens are not totally impotent against the
newly resistant parasites. But there has been a rapid increase in what they
call "slow clearing" of infections.
The proportion of patients with the slowest response to treatment in
western Thailand has increased from less than 1 percent in 2001 to 20 percent
in 2010.
The biggest fear is that resistant forms of malaria will emerge in
sub-Saharan Africa, where malaria afflicts and kills more people than anywhere
else.
Uhlemann and Fidock say malaria fighters are in a race against time.
Increased resistance to ACT "emphasizes the need to both monitor for signs
of emergence resistance," they write, "and implement all available
measures towards malaria elimination while we can."
RICHARD KNOX
npr.org
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