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2020 is the year of the rat. The rat is the first of the 12 Chinese zodiac signs, and represents spirit,
alertness, flexibility and vitality. In respiratory medicine, we may think of rats as vectors for diseases, such
as pulmonary forms of hantavirus disease or leptospirosis, and pneumonic plague. Rodent control is thus
part of hygiene guidelines and the International Health Regulations. And yet, the rat’s keen sense of smell
has led to its incredible career as a living tuberculosis (TB) detector.
The TB detection rat journey began with an idea in Tanzania in 2001, roughly 120 years after the
TB-causing Mycobacterium tuberculosis was discovered by microscopy and bacterial culture. African giant
pouched rats (Cricetomys ansorgei) had already been successfully trained using positive reinforcement to
find explosives [1]. So, the question arose if they could do more for humanity by helping to also combat
disease. But how would the rats use their noses to find bacteria or otherwise sniff out TB patients? For
centuries, olfaction had already informed diagnostics in medical practices, e.g. in detecting metabolic issues
such as ketoacidosis or tissue decay such as gangrene [2]. In the Flemish common language, the word
tering, which etymologically refers to the smell of tar, is used for TB. The advent of chromatographic
techniques allows characterisation of the organic compounds causing odours. |
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