An alarming new study has found that rats can sniff out tuberculosis much better than the standard swab test.
When trained to detect the disease in spit samples, the rats spotted 68 percent more cases than the microscopy test which doctors use.
They did this by learning the specific odor which tuberculosis-infected mucus emits.
The finding, published in the journal Pediatric Research, is the latest damning evidence that the relatively cheap swab test needs a long-awaited update.
The rats spotted 68 percent more cases than the microscopy test which doctors use, researchers in Tanzania discovered
The microscopy test has always offered mixed results, though it is one of the standard treatments around the world, including in the US and regions hard-hit by TB like south-east Asia.
Crucially, it relies heavily on the quality of the sputum – saliva and mucus – and children often struggle to produce enough to be tested.
It means the test often presents false-negatives.
‘Many children with TB are not bacteriologically confirmed or even diagnosed, which then has major implications for their possible successful treatment,’ lead author Georgies Mgode, from the Sokoine University of Agriculture in Tanzania, said.
In the US, patients typically start with a skin test and a chest x-ray, with the microscopy test to confirm the diagnosis. In poorer nations, the microscopy test is the first-line method because it is so cheap.
While TB has been steadily declining in most of the US, 20 states saw an increase in rates last year. Meanwhile in Asia and Africa, rates are soaring.
As a result, there has been a global push to rectify the issue with testing.
Previously, scientists have trained rats to detect landmine explosive fumes to monitor toxic exposure to humans.
Mgode’s team decided to try a similar tactic with tuberculosis, to see how clear a marker the odor of TB samples really is.
They trained African giant pouched rats to pick up the smell of molecules released by Mycobacterium tuberculosis bacterium, which causes TB, in sputum.
The team got sputum samples from 982 children in Dar es Salaam under the age of five who had already undergone a microscopy test.
Based on the test alone, 34 of them were diagnosed with TB.
The rats, however, identified another 57 cases of TB from the samples, which were cross-tested by a WHO researcher and confirmed.
On confirming the results, the researchers tracked down the remaining 57 children to get them treated.
Mgode said the findings show the current treatment and testing methods are woefully underdeveloped.
‘This intervention involving TB screening by trained rats and community based patient tracking of new TB patients missed by hospitals enables treatment initiation of up to 70 percent. This is a significant proportion given that these additional patients were considered TB negative in hospitals, hence were initially left untreated,’ Mgode said.