Rats better than people at diagnosing TB

Posted by Emma Woollacott

Want to know if you've got TB? Just spit on a rat. A new study has shown that trained giant African rats are 44 percent better at detecting the disease than trained people using microscopy.

The study collected sputum samples from 10,523 patients in Tanzania. They were first analyzed through microscopy by technicians at Direct Observation Treatment Short-Course (DOTS) centers, and then by the rats.

TB is the most lethal infectious disease in the world, causing around three million deaths per year.

While traditional microscopic analysis found 13.3 percent of patients to be TB-positive, second-line screening by the rats revealed 620 new TB-positive patients.

"Using sniffer rats to detect TB seems medieval but our study shows it works, providing an inexpensive, accurate, quick diagnostic," says lead investigator Alan Poling of Western Michigan University.

"This could have a huge impact in developing countries where TB accounts for one-fourth of all preventable adult deaths and high-tech screening methods aren’t readily available."

Rats, presumably, are.

Ten giant African pouched rats - Cricetomys gambianus - were trained to screen sputum samples. They were rewarded with banana for pausing at sputum samples known to contain M tuberculosis, but not for stopping at other samples.

This, however, raises one problem over the validity of the test which the researchers fail to address. To qualify as a true control group, the spectroscopy technicians should surely have received the same reward for a correct diagnosis as the rats.

Were they given bananas too? We think we should be told.