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[DAR ES SALAAM] Scientists in Tanzania have successfully trained rats to detect tuberculosis (TB) in human saliva by smell, using techniques first developed to teach the animals to find landmines.

The project has been carried out at the Sokoine University of Agriculture in Morogoro. Researchers found that while a laboratory technician, using a microscope, can analyse only 20 samples of saliva a day, a trained rat can analyse about 120 to 150 samples in just 30 minutes.

"Millions of people worldwide suffer from TB," says the project director, Bart Weetjens. "To them and their relatives, this [discovery] is very good news, and we have started to receive calls from all over the world."

Both wild and laboratory-bred rats (Cricetomys gambianus) required four to six months of training to be able to detect TB bacteria successfully. According to Weetjens, it requires little human skill to train them, as the rats only have to be exposed to the smell that they need to recognise.

The research was carried out last year using samples of human saliva from patients in the Muhimbili National Hospital in Dar es Salaam, and Morogoro Regional Hospital.

Weetjens adds that the main challenge is now to generate a sufficient supply of trained rats. He says that the World Bank has agreed to provide a grant of more than US$160,000 to help achieve this.

According to the World Health Organisation, worldwide deaths from tuberculosis are expected to increase from 2 million this year to 8 million by 2015. The situation has been exacerbated by the close association between TB and HIV/AIDS.

Weetjens points out that since about 40 per cent of the 60,000 Tanzanians suffering from TB are HIV-positive, detecting TB at an earlier stage raises the chance of securing effective treatment for both diseases.

He says that it is the speed and accuracy with which the rats can detect the TB infection that has encouraged researchers. "With this discovery, TB patients will be able to undergo early treatment in large numbers," he says.

The university has already trained about 300 rats to detect landmines, but only a few are trained to detect TB bacteria. The World Bank grant will make it possible to train up to 400 rats for TB detection.

Part of the grant will also be spent on building a new laboratory for TB testing at a centre run by Apopo, a Belgian-funded research group based in Antwerp that runs the landmine training centre. Twenty rats have already been sent to Mozambique, where they are currently engaged in detecting landmines left over from the country's civil war.

Weetjens points out that rat detection of TB is a cheap and affordable technique, as the animals have a highly developed sense of smell, and are easy to tame and train, as well as to maintain and transport. Furthermore they are found all over the African continent, adapt easily to new environments, and appear to enjoy performing repetitive tasks.