In the end we are attempting to change the parasite's environment to
suppress the population. We have seen more apparently promising
strategies that remain somewhat thwarted, so optimism here is
difficult. Yet it is one more new strategy that may surprise us.
I think that we can bring down the level of general infection load to
a point that the effect can be minimized with methods like this.
After all, that is what has happened with HIV.
Neither malaria or HIV is cured today however promising present
efforts appear. Yet we do understand that suppressing the load
sufficiently is actually good enough to ensure victims actually die
of old age.
Malaria hope:
Bacteria that make mosquitoes resistant
9 May 2013
By James Gallagher
Researchers have found
a strain of bacteria that can infect mosquitoes and make them
resistant to the malaria parasite.
The study, in the
journal Science, showed the parasite struggled to survive in infected
mosquitoes.
Malaria is spread
between people by the insects so it is hoped that giving mosquitoes
malaria immunity could reduce human cases.
Experts said this was
a first, distant prospect for malaria control.
Malaria is a major
global disease. The World Health Organization estimates that 220
million people are infected annually and 660,000 die.
Challenge
The study at Michigan
State University in the US looked at the Wolbachia bacterium,
which commonly infects insects.
It passes only from
females to their offspring. In some insects the bug is exceptionally
good at manipulating insects to boost the number of females for its
own ends.
Wolbachia kills male
embryos in some butterflies and ladybirds. In other situations, it
can produce males that can breed only with infected females, and even
allows some female wasps to give birth without mating.
Malaria-carrying
Anopheles mosquitoes are not naturally plagued byWolbachia, yet
laboratory studies have shown that temporary infection made the
insects immune to the malaria parasite.
The challenge was to
turn a temporary infection into one that would be passed on. The
research team found a strain of Wolbachia that could persist in one
species of mosquito, Anopheles stephensi, for the entire length of
the study - 34 generations.
Malaria parasites
found it difficult to cope in these mosquitoes, with parasite levels
fourfold lower than in uninfected bugs.
Research in Australia
has shown that a different strain of Wolbachia can prevent
the spread of dengue fever by mosquitoes. That research is more
advanced and has been shown to work in large trials in the wild.
Dr Anthony Fauci,
director of the National Institute of Allergy and Infectious Diseases
in the US, said this study was a proof of concept that the same could
be done for malaria.
"If you can get
it to survive and proliferate in the environment of mosquitoes in
malaria-stricken areas, this could conceivably have an important
impact on the control of malaria.
"I think the
potential for this is very important. The implementation will be the
challenge."
'Struggle to spread'
Commenting on the
study, Prof David Conway, of the London School of Hygiene &
Tropical Medicine, said: "It is interesting and is the first
report of Wolbachia clearly replicating, but a number of
things took away the punch."
He said the infected
females produced fewer eggs than uninfected females, which meant the
infection would struggle to spread in the real world.
Also he cautioned that
it was in just one species, Anopheles stephensi, which carries
malaria in the Middle East and South Asia. Anopheles gambiae, in
Africa, is a bigger problem.
One of the
researchers, Dr Zhiyong Xi, told the BBC: "We have done only one
strain. If we target Anopheles gambiae we would need to
apply the same technique again."
He added that if it
could be shown to work then "the Wolbachia tool can
complement currently available tools", such as mosquito nets and
medication.
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