Researchers have found a new way of testing for tuberculosis that is fast, cheap and widely available: large rats that can smell the bacteria in a sputum sample.
There are expensive and complicated laboratory tests for tuberculosis, and the World Health Organization recently endorsed a new machine that can give accurate results in under two hours. But the device costs $17,000, and each test requires a $17 cartridge.
Whatever else can be said about them, rats are cheaper.
Today, the most commonly used detection method in developing countries is smear microscopy. This 100-year-old technique involves collecting sputum, dyeing it with a substance that colors only Mycobacterium tuberculosis, the germ that causes TB, and examining the sample under a microscope.
The technique can be used in places where facilities are minimal, but it is not very sensitive — unless there is a high concentration of them, the bacilli are easy to miss, and that results in as many as 60 to 80 percent of positive cases going undiagnosed.
Studies suggest that the Gambian pouched rat can do better. The animal, an omnivorous rodent with puffy cheeks and that chillingly familiar rat body and tail, weighs 10 to 15 pounds and thrives in colonies of up to 20 all over sub-Saharan Africa.
The Gambian pouched rat apparently can smell the difference between tuberculosis bacilli and the myriad other germs that inhabit human phlegm.
The lead author of one study on the rats, Alan Poling, a professor of psychology at Western Michigan University, said that while the animals had been accepted as a reasonable diagnostic tool in Tanzania, “the medical community is still skeptical.”