SNIFFING OUT DISEASE FEATUREworld’s best and most enthusiastic sensor.
LAB REPORT
A dog’s nose has 300 million receptors
compared with our 5 million. In the same
way as they point out illegal drugs in
airports, dogs could be trained to sniff
people’s a nk les for mala ria, says Prof
Steve Lindsay of Durham University’s
biosciences department.
The team worked with researchers in
the Gambia to collect body odour samples
f rom schoolch ild ren, a sk i ng t hem to
wear nylon socks overnight. They also
carried out blood tests to see which of
the children had the malaria parasite:
30 of 175 children tested positive. None
of the children had symptoms.
Then they presented the socks to two
dogs trained to recognise malaria at
the UK charity, Medical Detection Dogs
(MDD). The dogs correctly detected the
smell of mala ria in 80 per cent of t he
samples from children who were positive
for the infection. Among those who did
not have the infection, the dogs got 91
per cent right.
“We t h i n k t he m a la r ia odou r is so
strong that the dogs can probably pick
someone out f rom a c rowd. So we’r e
looking at using the dogs at ports of entry
to countries to detect people carrying the
malaria parasite,” says Lindsay.
Once they’re spotted, they can be treated
before they spread the infection. “If it
works well, we have a fast, non-invasive
and affordable test to help keep countries
malaria-free,” he explains. “It might even
be possible to eradicate malaria.”
Other than detecting malaria, dogs are
already known for their skill in sniffing
out cancers, and are being studied for
several other conditions. But they aren’t
the perfect answer for all our medical
woes. They’re not likely to be installed in
every GP surgery, for instance. And you
can only work with a dog for a short time
before it loses concentration. In contrast,
a machine can keep going forever.
That’s where Logan’s bottled malaria
smell comes in ha ndy. The chemicals
can be used to develop a device that 2
TAKING THE SMELL TE ST
Joy Milne is a ‘super-smeller’. These people have a superior sense of smell
and are sometimes sought a er by perfume or wine manufacturers.
For Joy, however, her sensitive nose meant that she detected an unusual
odour on her husband, Les. Initially she thought that perhaps he wasn’t
showering enough, but 12 years later he was diagnosed with Parkinson’s
disease. She only made the connection between the condition and the
aroma a er noticing the same smell on people at a Parkinson’s disease
support group. She has since worked with scientists at the University of
Manchester to identify the chemicals underlying what she says is the
characteristic smell of the condition, which could help lead to earlier
diagnosis. Joy is now the linchpin for ongoing smell research. This is what
she says about some common diseases:- PARKINSON’S DISEASE
This is a musky smell. It can become acrid due to a build-up of bacteria and
yeasts in the sebum, the greasy substance that is secreted by our skin and
overproduced in Parkinson’s. - ALZHEIMER’S DISEASE
This has a milder human musk, like rye bread. The skin has a creamy yeast
smell which can become stronger as the disease progresses. - TUBERCULOSIS (TB)
TB has an odour like stale beer. The smell is present in the breath, and
changes as the disease progresses. The skin smells like “wet brown
cardboard and brine”. - CANCER
This smells of yeast or fungi, and di erent types of cancers have their own
smell. It may also be possible to smell the di erence when a patient is in
remission following treatment. - DIABETES
Diabetes has a sweet smell with the combination of citrus and creamy
pineapple. The smell can vary throughout the day, re ecting uctuations in
glucose levels and how well the diabetes is controlled.
Five diseases with telltale odours
Joy, who can smell
Parkinson’s disease,
meets a rat that can sni
out tuberculosis