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Last Updated: Monday, 1 March, 2004, 02:39 GMT
Rats help sniff out TB
By Daniel Dickinson
BBC, Dar es Salaam, Tanzania

Eusibio the rat
Eusibio has been trained to detect TB
A rat runs up and down a see-through perspex cage sniffing at a series of holes its base, where saliva samples - one positive for tuberculosis - have been randomly placed.

The rat sniffs and scratches at the hole with the TB sample, and is rewarded with a small piece of banana.

This is Eusebio, an African Giant Pouched rat, one of around 300 well-fed and highly-trained rodents at the Apopo research centre at the University of Sokoine in Morogoro.

Scientists at the centre are hoping to radically change the way TB is diagnosed using the exceptional sniffing abilities of these rats.
In Tanzania the need for a quick and effective way to diagnose TB is extremely important
Bart Weetjens, Apopo

In early clinical tests, it has proved to be a cheap and relatively accurate diagnostic tool, one that could be copied in laboratories across the developing world.

The team of scientists have been putting the rats through their paces over the last few months.

'Better than a human'

It is not easy to graduate from the rat programme at Apopo, according to Judith Karue, a specialist rat trainer.

She says: "The rats undergo up to four months of intensive training. The food reward system means that they are eager to learn and to find the right sample."

The clinical tests at Apopo suggest that rats are a highly effective diagnostic tool.

The success rate for diagnosing positive sputum samples from the lungs of TB patients is 67%, higher than the standard developing-world diagnostic approach using a microscope, which Apopo puts at just 60%.

Rats can identify them because of the distinct smell of the chemicals in infected sputum samples.

Bart Weetjens, the centre's director, told BBC News Online that the success rate is only part of the story.

A rat in training
A rat being trained to detect TB
"A rat can diagnose up to 2,000 samples a day compared to a laboratory technician who can carry out a maximum of around twenty using a microscope."

It is also a diagnostic tool which is appropriate to the developing world.

The rats can simply be picked from the African bush and then bred.

It is easy to teach people how to train them and the training itself, although time consuming, is not expensive.

The upkeep of the rats is also considerably less than a laboratory and technician.

Landmines work

There is a global push to eradicate TB. The World Health Organization estimates that, worldwide, deaths from the disease could increase to eight million a year by 2015.

Bart Weetjens says: "In Tanzania the need for a quick and effective way to diagnose TB is extremely important because of the HIV/Aids situation.

"Up to 40% of TB cases are HIV/Aids related. If we can diagnose the disease early on, people will live longer."

His team's findings have created a huge amount of interest in the medical world.

The World Bank has provided a grant of US$160,000 to build extra laboratories, carry out more clinical trials and train up to 400 TB sniffing rats.

Further research may even provide Apopo with new ideas on how to use the olfactory powers of rats.

It is already using rats to sniff out landmines, but according to Bart Weetjens there may be other medical applications.

"We know that dogs can sniff out prostate and skin cancers so rats should be able to do the same.

"There may be other pathogens [disease-causing organisms] that can be detected by the animals."

Meanwhile, the new team of rats is due to be put into training in the common months.

If the detection rates consistently reach 67%, then it's likely this new diagnostic tool could be rolled out in hospitals across Tanzania and indeed in other African countries in the near future.

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