For decades, health officials have battled malaria with insecticides, bed
nets and drugs. Now, scientists say there might be a potent new tool to fight
the deadly mosquito-borne disease: the stench of human feet.
In a laboratory study, researchers found that mosquitoes infected with the
tropical disease were more attracted to human odours from a dirty sock than
those that didn't carry malaria. Insects carrying malaria parasites were three
times more likely to be drawn to the stinky stockings.
The new finding may help create traps that target only malaria-carrying
mosquitoes, researchers say.
"Smelly feet have a use after all," said Dr James Logan, who headed the
research at the London School of Hygiene and Tropical Medicine. "Every time we
identify a new part of how the malaria mosquito interacts with us, we're one
step closer to controlling it better."
Mozzies and human odour
Malaria is estimated to kill more than 600 000 people every year, mostly
children in Africa.
Experts have long known that mosquitoes are drawn to human odours, but it was
unclear if being infected with malaria made them even more attracted to us.
Infected mosquitoes are believed to make up about 1% of the mosquito
Using traps that only target malaria mosquitoes could result in fewer
mosquitoes becoming resistant to the insecticides used to kill them. And it
would likely be difficult for the insects to evade traps based on their sense of
smell, scientists say.
"The only way mosquitoes could (develop resistance) is if they were less
attracted to human odours," said Andrew Read, a professor of biology and
entomology at the University of Pennsylvania, who was not part of Logan's
research. "And if they did that and started feeding on something else - like
cows - that would be fine."
Read said the same strategy might also work to target insects that carry
other diseases such as dengue and Japanese encephalitis.
How the study was done
In a related study, Logan and colleagues also sealed human volunteers into a
foil bag to collect their body odour as they grew hot and sweaty. The odours
were then piped into a tube next door, alongside another tube untainted by human
odour. Afterwards, mosquitoes were released and had the option of flying into
either tube. The insects buzzed in droves into the smelly tube.
Logan said the next step is to identify the chemicals in human foot odour so
that it can be made synthetically for mosquito traps. But given mosquitoes'
highly developed sense of smell, getting that formula right will be
Some smelly cheeses have the same odour as feet, Logan noted.
"But mosquitoes aren't attracted to cheese because they've evolved to know
the difference," he said. "You have to get the mixture, ratios and
concentrations of those chemicals exactly right otherwise the mosquito won't
think it's a human."
Scientists said it's crucial to understand the subtleties of mosquito
behaviour. Other studies have shown mosquitoes don't become attracted to humans
for about two weeks - the time it takes for the malaria parasites to become
infectious for humans.
"At the moment, we only have these glimpses of how parasites are manipulating
the mosquitoes," said George Christophides, chair of infectious disease and
immunity at Imperial College London. "We need to exploit that information to
help us control malaria."