Yesterday, from my window, I saw a rat running across our backyard. Rats have a tough life. Nobody likes them. We hate them, poison them, kill them in whatever way we can. At best, rats belong in our sewage system. Rats bring diseases like the plague, they eat our harvest and cause hunger. They’re vermin - basta.
But now I felt sorry for the rat in my garden and did not even tell my wife about it. She might have asked me to go outside and kill it, which I no longer will do. Not now, not in future. Because I have started to like rats.
What follows is the story of APOPO, a group of rat lovers that started a social enterprise with operations in Tanzania and Mozambique. Its founder, Bart Weetjens (Belgian), picked on the idea that the olfactory system (i.e. the nose) of rats is extremely advanced and very sensitive. In some old literature from the 1970s Weetjens’ eye fell on a story that rats can pick up the scent of trinitrotoluene (TNT), the explosive used in landmines. Given the fact that most mine-clearing processes are slow and expensive, the rat lovers thought of setting up a programme to use rats for this purpose. And with massive success (see their 2009 annual report here).
Rats go to school
The APOPO staffs are experts in training the African Giant Pouched Rat (Cricetomys gambianus) to detect mines. Young rats first undergo a phase of socialisation, where they get used to working with people. Then follows the ‘click’ phase, where display of desired behaviour is rewarded with a bit of food. If the rat does what the trainer wants, he uses a click sound to reinforce the behaviour resulting in the reward. Slowly but surely, the rats figure out that mine detection yields a piece of banana, and so turn into expert mine detectors.
APOPO has been active in Mozambique since 2003. Both during the independence war (1964-1974) and the civil war (1977-1992) all ten provinces of Mozambique got littered with landmines. A recent survey declared more than 12 million square metres as mined areas in 541 sites in six provinces. But during 2008-2009 the good rats already turned 440 thousand square meters into safe land again after detecting some 200 mines. By 2013 they hope to have cleared nearly a third of all mined areas. Turning dangerous land into agricultural land. And you know what? The rats do it at half the price of conventional methods ($ 1,18 per square meter). APOPO call their rodent staff HeroRATs. They sure are.
And the story gets better. Weetjens and his crew thought of tackling another major killer: tuberculosis (part of MDG6). They thought of detecting the specific smell of the causative organisms, the TB bacilli, in the sputum of humans. Using much the same principle of training the rats to display arrestment behaviour when they encounter some spit with the smell of TB, they have now developed it into a full programme. In 2008/9 the rats sniffed out the spit of some 46 thousand Tanzanians. What’s more, they detected TB in 561 of these samples that were not detected using microscopy. You can’t fool a rat. APOPO estimated that they averted 13 thousand TB transmissions now that the HeroRATs led to patients receiving appropriate DOTS treatment.
What’s the big deal?
First, this isn’t ‘low tech’, it is ‘no tech’. Using simple yet highly sensitive and specific approaches that are suitable for low-income countries that cannot afford expensive laboratory equipment to detect TB using PCR or other DNA-based methods, or advanced detection equipment for mines.
Second, APOPO shows us that solutions to problems in the developing world can be tackled by solutions that would not be used in the developed world. Their starting point was rural Mozambique, and thinking of solutions from 'within' rather than adopting solutions from 'outside'.
Large sums of money are being spent on the development of electronic noses for TB detection. These may come one day, but again may not be affordable for low-income countries. Or will be technologically complex and prone to faltering under harsh field conditions.
Last year a colleague of mine submitted a project to the Gates Foundation to train dogs to detect the transmissible stage of the malaria parasite in humans (the gametocyte; see life-cycle here). He didn’t get funded, but the APOPO story makes me confident that we should re-visit the idea…
HeroRATs: I love them. It's development at its best.