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 African Giant Pouched Rats trained by the Belgian non governmental
organization APOPO are widely known for their work sniffing out
landmines, and are now developing a reputation in East Africa for
their skill and speed at detecting TB too.
Tuberculosis is the leading cause of death, after HIV, from an
infectious disease. Around the world, there are about 9 million new
cases a year and around 2 million deaths, according to the World
Health Organization.
In Tanzania, people in communities where TB is most common,
including prisons, often fail to show up for screening because of
lack of money or awareness, creating a huge burden for health
authorities trying to tackle the disease, health officials said.
Because existing systems lack the accuracy, speed and
cost-efficiency required to scale up screening of the highly
contagious disease, many TB cases go undiagnosed, they said.
APOPO, with funding from the United States Agency for International
Development (USAID,) plans to recruit and train more rats to carry
out prison screening that it expects to be faster and more reliable
than existing methods.
“We believe our unique TB Detection Rat technology will prove itself
as an effective mass-screening tool," said APOPO's U.S. director,
Charlie Richter.
"We then aim to expand the program to all prisons, shantytowns,
factories and other settings in Tanzania, Mozambique and other high
TB-burden countries, as well as in high-risk groups such as those
individuals living with HIV/AIDS. This will improve and save lives
all over the globe at a low cost,” Richter said.
Though data from African jails is hard to come by, studies from
Tanzania, Malawi and Ivory Coast show that TB rates are 10 times
higher in prisons than in the general population, according to the
U.S. Centers for Disease Control and Prevention.
TRAINING STARTS AT FOUR WEEKS OLD
APOPO says the rats undergo a rigorous training process that begins
when they are four weeks old. As soon as the rats open their eyes,
they are introduced to various stimuli and learn how to socialize
and interact with people.
The rats learn to recognize the presence of TB in samples of sputum,
mucus that is coughed up from the patient’s lower airways, and
rewarded when they succeed.
The testing process starts when a rat is presented with a row of 10
sputum samples, and when it detects TB the rat hovers over the
sample for 3 seconds, Richter said.
The rats' accuracy at detecting TB is almost 100 percent, but they
cannot distinguish between normal and drug-resistant strains, APOPO
scientists say.
The APOPO system is fast, cheap and has the potential to greatly
lower screening costs in poor countries, Richter said.
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While a laboratory technician may take four days to detect
tuberculosis, a trained rat can screen 100 samples in 20 minutes,
and a rat screening can cost as little as 20 US cents when APOPO
operations are running near capacity, he said.
APOPO’s current program have screened more than 340,000 TB samples,
halting over 36,000 further infections, and increased detection
rates by over 40 percent in several partnered clinics, officials
said.
Khadija Abraham, an expert at Tanzania’s National Leprosy and
Tuberculosis Programme, said trained rats had a great ability to
detect a wide range of strong-smelling molecules that could help
tracking down undiagnosed TB cases, especially in rural areas.
"Training an animal with a strong and reliable sense of smell to
help detect disease in a vast country like Tanzania could
potentially offer a valuable solution to help detecting the
disease," she told the Thomson Reuters Foundation.
Training pouched rats requires little human skill since they only
have to be exposed to the smell they need to recognize, Abraham
said.
“Experiments show that these rats can detect a sample with TB
parasites in a second and evidence has shown that they are able to
sniff out even those with very minimal parasites,”she said.
TB cases are normally detected by sputum smear microscopy, a slow
and costly process that has not changed for years and is not very
accurate. The WHO insists that one lab technician should not test
more than 20 patients a day, and says the chances of misdiagnosis
are high if this exceeded.
(Corrects name of U.S. organization in paragraph 9)
(Editing by Tim Pearce; Please credit the Thomson Reuters
Foundation, the charitable arm of Thomson Reuters, which covers
humanitarian news, women's rights, corruption, climate change. Visit
http://news.trust.org)
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