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Rats that can smell the tuberculosis (TB) bacterium in a sputum sample could be more effective in detecting TB than expensive laboratory tests, a study suggests.

The Gambian pouched rat (Cricetomys gambianus), found all over Sub-Saharan Africa, can smell the difference between TB bacteria and other germs found in human phlegm, according to researchers writing in The American Journal of Tropical Medicine and Hygiene last month (December).

They found that the rats could identify the bacterium with 86 per cent accuracy and picked up 44 per cent more positive cases than microscopy.

Although rats are already used to detect TB in Tanzania, "the medical community is still sceptical" said Alan Poling, a behavioural scientist at the charity Detection Rats Technology — APOPO, in Tanzania, and a psychology professor at Western Michigan University, United States.

Current TB tests are costly and complicated. The WHO recently approved a device that provides accurate results in less than two hours — at a cost of US$17,000 and an additional US$17 for each test.

But even those that have studied the rats remain sceptical of using the method to detect TB in the field.

"They're a long way from demonstrating the robustness of their technique," said Neil W. Schluger, a professor of medicine at Columbia University, United States, who specialises in lung diseases.

"These rats can do something amazing," he added, "but even if you accept that it worked within their lab, are they still good at it a year later? Do they all have to be trained by the same person? How do they have to be cared for? If you change their cage or their bedding, does it still work?"

See below for a Voice of America video about Gambian pouched rats detecting TB:



The American Journal of Tropical Medicine and Hygiene doi:10.4269/ajtmh.2010.10-0180 (2010)

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