Tuberulosis (pronounced too-ber-kew-LO-sis and also known as TB) is the second most deadly infectious disease in the world, killing around 2 million people per year. The World Health Organisation (WHO) estimates that there are 9 million new cases every year; the TB bacteria spreads when someone inhales tiny droplets of moisture from the coughs or sneezes of an infected person. Symptoms include a persistent cough that brings up phlegm and sometimes blood, weight loss, night sweats, fever and tiredness.
The most common test for tuberculosis is called sputum smear microscopy. The patient collects a sample of their sputum (also known as phlegm), and a thin layer of it is smeared onto a glass slide and examined under a microscope. It’s a cheap and simple test and people can be trained to do it fairly easily; it’s also quick, usually only taking a few hours before the results are known. Unfortunately it’s not always accurate and in some areas this method has been shown to detect only 50-60% of tuberculosis infections. In addition people in affected countries often don’t attend screenings, either through a lack of awareness or a lack of money.
Now, though, there’s a new way of detecting the tuberculosis bacteria in sputum and it’s almost 100% accurate. African Giant Pouched Rats are being trained by scientists from APOPO, a Belgian non-governmental organisation that also trains rats to detect landmines. The training process begins when the rats are just 4 weeks old, and to begin with they’re just taught how to interact and socialise with people. They learn how to recognise the presence of TB in sputum samples because they’re rewarded when they correctly identify the infected sputum. A trained rat can screen 100 samples in just 20 minutes.
The rats are being used to detect tuberculosis in prisoners in Tanzania and Mozambique. Because prisons have large populations in confined conditions, they’re the perfect place for a bacteria like TB to spread; infection rates in Tanzania’s prisons are 10 times higher than in the general population. So far the rats have screened over 340,000 samples and increased detection rates by more than 40%. Thanks to funding from the United States Agency for International Development (USAID) there are currently 9 rats working in Maputo, Mozambique and another 50 in Morogoro, Tanzania. Once the rats’ success becomes more widely known APOPO plans to expand the programme to other settings, including shantytowns and factories.