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 Scientists are racing to develop new insecticides, warning that tens
of thousands of people in Africa could die every year if mosquitoes
develop full resistance before replacements are found.
The issue will be a concern when the World Health Assembly meets in
Geneva next month to look at proposals to eliminate malaria in 35
countries by 2030.
An estimated 4.3 million deaths have been prevented since 2000, many
of them because of the mass distribution of treated bed nets in
Africa, according to Roll Back Malaria, a partnership including the
World Health Organization, UNICEF and World Bank.
"Only one class of chemicals is registered and works in bed nets.
It's a unique chemistry and it's very hard to replace," said Nick
Hamon, CEO of IVCC, a UK-based charity working with agro-chemical
companies to develop new insecticides against mosquitoes.
The chemicals currently used are extremely safe for humans, are
absorbed through the insects' feet -- they do not have to be eaten
-- and kill them within minutes. They also last for several years on
the nets and are affordable.
A lot of hopes are pinned on three new chemicals which IVCC and its
partners are putting into development this year. But even if these
succeed, it will take them eight to nine years to reach the market.
Scientists are also looking at insecticides already used in
agriculture that may be repurposed for health uses, and which could
become available more quickly.
In the meantime, tens of thousands of people may die each year if
mosquitoes develop full resistance to the current insecticides,
Hamon said.
He said it was a dilemma knowing how much to warn people about the
dangers of resistance.
"You've got to shout loudly enough that people go: 'Right we've got
to fix it', but you don't want to risk the lives of people, (if
health agencies) say: 'What's the point? We'll just shut down all
our (bed net) programs'," he said in an interview.
Scientists say even untreated bed nets can play an important role in
protecting people from the disease, which kills more than 580,000
people a year.
Treated bed nets were rolled out on a massive scale in Africa in the
mid-2000s, with the aim of reaching every person in affected
countries, but by the end of the decade scientists realized
resistance was becoming a problem.
"If that resistance goes on getting worse then we will get to the
point where our treated nets aren't really working much better than
untreated nets," said Jo Lines, co-chair of Roll Back Malaria's
Vector Control Working Group and a malaria expert at the London
School of Hygiene and Tropical Medicine.
Adding insecticides to bed nets doubles their protection, Lines
said.
The chemicals going into development this year may create a new
generation of insecticides. If two or all three of them are
successful and are used in combination, they could become a powerful
new weapon, Lines added.
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"It would make getting resistance much harder for the insects. Not
impossible, but much harder," he said.
EXITING THE ARMS RACE
But experts say the question remains how long it will be before
mosquitoes do develop resistance to them.
"We can't keep replacing insecticides every (few) years forever,"
Lines said.
"In the long run we need an exit from this arms race. Either that,
or we need to tone down the (insecticide) coverage."
In agriculture, insecticides are only used in certain areas, slowing
down the development of resistance.
But that is more difficult to do in the case of health. One
possibility could be to use untreated bed nets in areas with
relatively little malaria, and keep the treated ones for areas with
high rates of transmission, Lines said.
Other ways to control the disease include releasing genetically
modified mosquitoes or sterilized mosquitoes to reduce mosquitoes'
ability to breed. This could help stabilizes the situation but is
not a long-term solution, Lines said.
Vaccines are another possibility, and the first one may be approved
for use in Africa from October.
But any vaccine would have to be highly effective to work in parts
of Africa where malaria transmission is very strong, Lines said.
In the long-run, scientists want to find ways both to eliminate
malaria in Africa and to prevent it returning.
Regions that have successfully eliminated malaria did so as they
developed economically, Lines said.
In Europe, North Africa, North America and, most recently, Sri
Lanka, families getting richer, improved health services, and
changes in housing and the landscape have played a big part, Lines
added.
For example, there is some evidence that having ceilings in houses
underneath roofs reduces the risk of malaria. "But do we put that
out there? No we don't," he said.
"What we have to do ... is look at things that will be integrated
into (everyday) life."
(Reporting by Alex Whiting, Editing by Emma Batha)
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