She worked weekdays, took weekends off—and saved thousands of lives. Now, Carolina the rat is finally enjoying her retirement.
For seven years, a giant African pouched rat named Carolina helped diagnose tuberculosis across East Africa, using nothing but her nose. Trained by the nonprofit APOPO, she detected over 3,000 cases of TB that local clinics missed—potentially saving more than 30,000 people from infection.
“She’s not just a rat—she’s our colleague,” said Cindy Fast, APOPO’s head trainer and a behavioral neuroscientist. “These animals are saving lives and changing how we view the creatures we usually dismiss.”
A Nose That Outperforms Machines
Unlike your average rodent, Carolina is a trained HeroRAT. She belongs to a cohort of giant African pouched rats specially raised to detect landmines and tuberculosis. Weighing up to nine pounds and with a nose powerful enough to detect trace chemicals, she can analyze 100 sputum samples in just 20 minutes—what would take a human four days to do.
“Most clinics rely on microscope testing that’s only about 20 to 40 percent accurate,” explained Dr. Tefera Agizew, APOPO’s head of tuberculosis programs. “Our rats boost detection rates by 40 percent. They are a critical part of our diagnostic strategy.”
Before deployment, each rat undergoes a full year of clicker training using banana-avocado smoothies as positive reinforcement. They must correctly identify 500 positive samples before being cleared to work.
“They’re clever and food-motivated,” Fast explained in the National Geographic feature. “We train them to ignore distractions like human scent or environmental noise and focus only on the TB biomarkers.”
Rats Are Helping Fight a Deadly Epidemic
Tuberculosis remains the leading cause of death by infectious disease worldwide—killing over 50,000 people in Tanzania and Ethiopia alone in 2023, according to Dr. Tess Ryckman, an epidemiologist at Johns Hopkins.
“People think TB is a disease of the past, but that’s not true,” Ryckman said. “It’s deeply linked to poverty, HIV, and undernutrition. And because of stigma, many people avoid testing.”
That’s where rats like Carolina step in. By working through sample backlogs and identifying missed cases, HeroRATS are helping curb TB’s spread. APOPO estimates their rats helped prevent more than 400,000 infections in just one year.
“For every person with TB that a rat finds, 10 to 15 more infections are prevented,” said Agizew. “That’s how powerful early detection is.”
A Fitting Farewell for a Lifesaving Rodent
In November, Carolina clocked out for the last time. APOPO staff gave her a proper sendoff—complete with a rat-safe carrot cake, peanuts, and applause.
“She had weekends off during her career,” Fast joked. “Now she’s fully retired in her own little Florida—an outdoor enclosure with toys and enrichment, shared with Gilbert, another retired rat.”
Some rats thrive in this work, like Tamasha, Fast’s current favorite: “She does a little happy dance before every shift and protests when it’s over. These animals enjoy the work—it’s a game to them.”
Others don’t take to it. But instead of being discarded, they’re reassigned. “A rat that doesn’t excel at landmine detection might become a superstar at TB detection,” Fast explained. “It’s about finding the right job for their personality.”
The Bigger Picture: Rethinking Unlikely Heroes
Carolina’s legacy isn’t just about medicine—it’s about changing minds. Creatures often seen as pests are proving to be vital allies.
“Not only are we saving people’s lives,” Fast said, “but we’re challenging assumptions about animals like rats. They’re not villains. They’re heroes.”
Other unusual animals are also making medical contributions. Gila monster venom has inspired diabetes treatments. Maggots clean wounds better than many modern methods. Spider silk is used to repair human ligaments.
Carolina may be retired—but her story will continue inspiring a new way to see the natural world.
