Non-profit organization APOPO ( web site ) in Tanzania trains rats to sniff out land mines and tuberculosis. Thousands of land mines have been found, and thousands of TB cases detected.
The hero rats of Africa sniff out land mines — and TB infections
A mine-detecting rat can check an area the size of a tennis court in about 30 minutes, a job that would take a de-mining worker with a metal detector up to four days. Since APOPO began, nearly 22 million square meters of land have been given back to local communities, more than 19,000 land mines have been located and deactivated and more than 82,000 items of unexploded ordnance, such as bombs and artillery shells, have been found and destroyed.
[ … ]
And since APOPO began its TB detection, more than 200,000 samples have been screened by rats, and more than 11,000 additional TB patients have been detected, with more than 165,000 additional infections prevented. A HeroRAT can check 100 samples of TB in less than 20 minutes, a job that takes a lab technician using a conventional microscope up to four days.
(ETA: I wonder if the rats are susceptible to catching TB doing that.)