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.
In 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.
AdvertisementUsing conventional laboratory analysis, technicians could only find 13 percent TB positive sputum samples.
The 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 the tuberculosis detection rate by lab technicians. The study was led by Alan Poling, at the University.
However, 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.
The 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 tuberculosis in human phlegm or 'sputum' samples, and to seek it out in return for a reward.
According to the researchers, a trained rat can test 10 samples in a minute. During the sniffing test, 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 Mountains. The species, cricetomys gambianus, was picked out for its brilliant sense of smell, intelligence, low maintenance costs and long lifespan in captivity.
However, it may be difficult to acquire accreditation for this new method because regulatory authorities are not used to this type of test.