Giant rats are probably not the first thing that come to mind to tackle tuberculosis but scientists hope their sniffing skills will speed up efforts to detect the deadly disease in major cities across the world.
Tuberculosis, which is curable and preventable, is one of the world's deadliest infectious diseases, according to the World Health Organization (WHO), killing 1.7 million people in 2016 and infecting 10.4 million others.
African Giant Pouched Rats, trained by Belgian charity APOPO, are known for sniffing out landmines in countries from Angola to Cambodia and for detecting TB cases in East Africa.
Over the next few years, APOPO plans to fight tuberculosis at the source by launching TB-detection rat facilities in major cities of 30 high-risk countries including Vietnam, India and Nigeria.
"One of the best ways to fight TB at source is in major cities that draw a lot of people from the rural areas," James Pursey, APOPO spokesman, told the Thomson Reuters Foundation.
"It is a vicious circle. You can be reinfected. To fight TB, you have to hit it hard," he said by phone from Zimbabwe.
Dr. Simon Angelo (L) examines Iman Steven suffering from tuberculosis, held by her mother (R) at the hospital of Doctors Without Borders (MSF), June 15, 2016, at the Protection of Civilians (PoC) site in Malakal, South Sudan.
Many people get infected in big, densely populated cities and spread the disease to rural areas, according to Pursey.
The rats learn to recognize the presence of TB in samples of mucus that is coughed up from the patient's lower airways.
In Tanzania, people in communities where TB is most common, including in prisons, often fail to show up for screening because of a lack of money or awareness, placing a huge burden on health authorities, health experts said.
"TB is a disease of poverty," said Pursey. "If nothing changes it can only get worse."
The APOPO has seen the TB detection rate increase by 40 percent in clinics it has worked with in Tanzania and Mozambique, according to Pursey, who said that using rats to screen did not negate the need for proper diagnostic testing.
While a technician may take four days to detect a case of TB, a trained rat can screen 100 samples in 20 minutes, and a rat screening costs as little as 20 US cents, APOPO said.