Scientists say that the sniffing abilities of
rats can help detect tuberculosis (TB) in sputum samples more efficiently and
at a lower cost than lab technicians using microscopes.
a recent study, researchers at Western Michigan University in Kalamazoo
compared the rats' ability to smell TB
against the skills of lab technicians testing more than 10,500 sputum samples.
conventional laboratory analysis, technicians could only find 13 percent TB
same samples were then examined by a group of 10 rats, and the second screening
found an additional 620 new TB-positive patients, a 44 percent increase over
detection rate by
lab technicians. The study was led by Alan Poling, at the University.
according to the experts, not all rats detect tuberculosis. They must be given
some training. Training
a rat to sniff out TB bacteria
takes around 9 months
and it begins once the baby rat opens its eyes when it is four-weeks old.
trainer puts the young rats in a basket in front of a bicycle, or lets
them walk around in the dirt and the grass, or takes the rats for a drive in
the car to get them used to different experiences.
After this socialisation
process, the rats are given training to recognise the odour of mycobacterium
human phlegm or 'sputum' samples, and to seek it out in return for a reward.
to the researchers, a trained rat can test 10 samples in a minute.
During the sniffing
, trainers load human phlegm samples from TB patients in batches
of 10 under small holes in the rats' rectangular glass and steel cages.
The rat darts from
sample to sample, briefly smelling each one, and scratching rapidly with both
front paws over any it finds are infected with tuberculosis.
Apopo, an NGO based in
Tanzania, has been using this method to detect TB for more than decade. The
organization is now conducting research on the method, and eventually hopes to
get accreditation from the World Health Organization.
The NGO's rats are
descendents of wild African pouched rats caught on the slopes of the Uluguru
. The species, cricetomys gambianus, was picked out for its
brilliant sense of
, intelligence, low maintenance costs and long lifespan
However, it may be
difficult to acquire accreditation for this new method because regulatory
authorities are not used to this type of test.