A rat the size of a rabbit twitches its nose over a row of plastic cups. Each cup holds a sputum sample from a patient told their tuberculosis test came back negative. The rat has around 20 minutes to recheck 100 of them. A human technician using standard microscopy would need at least four days.

A Nose That Standard Diagnostics Cannot Match

African giant pouched rats detect volatile organic compounds specific to Mycobacterium tuberculosis - compounds that smear microscopy often cannot identify, particularly in patients with low bacterial loads.

The Belgian nonprofit APOPO has trained these rats since 1997, calling them HeroRATs.

Each takes around nine months to reach full certification, learning to pause and signal over a positive sample before moving on.

The Numbers Behind the Speed

APOPO's own data is clear: one trained rat screens 100 samples in under 20 minutes, a task that takes a lab technician at least four days using conventional microscopy.

A 2024 study published in PLOS ONE examined over 43,000 sputum samples from more than 34,000 suspected TB patients across 69 Tanzanian health facilities.

Adding HeroRATs to the diagnostic process increased TB case detection by 48 percent overall - a 44 percent gain over Xpert testing, one of the most advanced tools available.

The cost per sample for a rat is approximately $1, versus $18 for an Xpert test.

The Second Job: Clearing Minefields

The same species also works across Africa and Southeast Asia sniffing out buried landmines and unexploded ordnance.

APOPO's mine-detection rats have located over 155,000 landmines and explosives, helping to restore safety to nearly two million people.

One rat can search 200 square meters in 20 minutes - work that would take a human deminer with a metal detector up to four days.

Unlike metal detectors, the rats ignore scrap metal and only respond to the scent of explosives. At one to two kilograms, they are too light to trigger any mine.

How They Are Trained

APOPO began as a research project at Antwerp University in Belgium and has since grown into an international operation across sub-Saharan Africa and Southeast Asia.

HeroRATs are trained using positive reinforcement - food rewards for correct detections - and live in APOPO's care for their entire lives.

The organisation also explores detection of other diseases where scent provides diagnostic clues that laboratory equipment misses.

Related Tags