The system used to detect tuberculosis in Mozambique is more than a century old—so researchers are asking some furry friends for help. Scientists have been teaching African giant pouched rats to alert them to infected mucus samples, National Geographic reports. The researchers slide the samples into the rats' cage, and if the creatures smell the bacterial illness, they scratch the floor. They're trained to "associate the smell of TB with a reward," says a manager of the operation. The project began in Mozambique last year and Tanzania in 2008; it's run by APOPO, a Belgian organization that also turns to rats for help discovering land mines, National Geographic notes.
The rats seem pretty good at their jobs. In Maputo, the country's capital, they picked up on 764 cases health clinics hadn't spotted, detecting 44% more than the humans had, investigators say. They can smell 100 samples in less than 20 minutes, per APOPO's site. Rats need months of training in the procedure, and that costs up to $8,000—but it's a lot cheaper than the $17,000 base cost for the latest TB-detecting technology. Right now, according to APOPO's website, there are 54 "accredited" rats. But their techniques aren't perfect, National Geographic notes: They can't tell when they're smelling an antibiotic-resistant strain of the disease, and just a quarter of the cases they identify are confirmed positive. (As for TB's arrival in the New World, we can apparently blame seals.)