The African giant pouched rat can be trained to sniff out tuberculosis more accurately than most lab tests.
So why is the medical profession still sceptical?
In a small hot room in a compound located in Tanzania’s lush southern highlands one day in mid-December were three white-clad technicians – a glass-and-metal chamber and a large brown rat named Charles.
After being gently dropped into the chamber Charles aimed his long snout towards the first of a series of 10 sliding metal plates in the chamber’s base.
A technician swiftly opened it – revealing a small hole.
Charles sniffed at it … and moved on.
The hole was closed and there was a clink as the next plate was yanked back.
This time Charles was gripped.
He sniffed hard – scratching at the metal – the five claws on each of his paws splayed with the pressure.
The technician called out: ‘Two!’
Over by the window her colleague held a chart which he kept raised so the others could not see it.
He inserted a tick.
I glanced over.
The chart was a grid of small boxes – 10 across by 10 down – each marked with a code.
Two of the boxes in each line were shaded grey.
The tick had been placed in a white box.
It is highly possible that Charles had just saved a person’s life.
Charles is an African giant pouched rat – a species endemic to sub-Saharan Africa.
He is also a pioneer – one of 30 of his species that live and work in Morogoro – a few hundred kilometres west of Tanzania’s largest city Dar es Salaam.
The rats are engaged in a programme to sniff out tuberculosis – a disease that can destroy the lungs.
About nine million new cases of TB are diagnosed worldwide every year – a quarter of them in Africa.
Africa also has the highest TB death rate per head of population.
Antibiotics can cure the disease but it is fatal if untreated and many patients are never diagnosed.
This is partly because the 125-year-old microscope-based test used across Tanzania (and in many other cash-strapped countries) picks up only about 60% of cases – and that figure drops as low as 20% for people also infected with HIV.
This is where Charles comes in.
He and his rodent colleagues sniff cough-and-spit samples provided by suspected TB patients.
The rats are not infallible but they do detect about 70% of cases whether or not a patient has HIV – which matters a great deal in Tanzania where about four in every 10 people with TB are HIV-positive.
That particular morning Charles sniffed 100 samples – missing one that had been identified as positive by the public clinic – shaded grey on the chart – but identifying 12 new suspected cases which would then go for secondary checking.