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05/01/2013

Training rats in Tanzania to detect tuberculosis

 

NPR's excellent health blog, Shots, has a post today that alerted me to a living, breathing, four-legged tool for diagnosing tuberculosis in low-resource areas: rats.

More specifically, giant African pouched rats -- a rodent that is native to most of Africa and has an excellent sense of smell.

Journalist and photographer Jonathan Kalan reports that a nonprofit organization called APOPO, which has been using the animals for landmine detection, is teaching giant African pouched rats to sniff out tuberculosis in samples of human sputum (mucus from the upper airways).

Kalan explains:

"The team trains the critters with a Pavlovian click-and-reward approach. When the rats are just a few weeks old, technicians teach the animals to associate a click sound with a small bite of mashed bananas and a special pellet of food. The next step is to link the scent of TB with the reward."

Basically, if the rats smell Mycobacterium tuberculosis in a sputum sample, they will pause over it; if they don't, they move on. (For more information, APOPO's website has a helpful infographic that explains how the process works).

Kalan interviewed chemist Negussie Beyene, who said that APOPO's trained rats (they have 54, according to the website) can accurately sniff out a TB sample roughly two-thirds of the time. When two or three rats are used, however, the accuracy rate increases to about 80 per cent.

Some rats are already being put to work at a lab in Morogoro, Tanzania, Kalan reports. And not only are the four-legged helpers catching positive samples being missed by lab workers, the smell test works much faster than microscopy -- the rodents can evaluate up to 200 samples in a session and one particular rat, named Harod The Rat, can perform 10 evaluations in just 20 seconds.

At least one study has shown that the rats can improve TB detection by 31.4 per cent. APOPO researchers have also published a paper about the use of rats in TB detection that includes some interesting data, which you can check out here.

Jennifer Yang is the Star’s global health reporter. She previously worked as a general assignment reporter and won a NNA in 2011 for her explanatory piece on the Chilean mining disaster. Follow her on Twitter: @jyangstar

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