HeroRats: The Battle Against TB
Tuberculosis (TB) is one of the deadliest infectious diseases globally. It killed an estimated 1.23 million people in 2024. TB is a bacterial disease that primarily affects the lungs and spreads when a person coughs or speaks. Because TB is a bacterial disease it can generally be cured with antibiotics but the challenge, especially in parts of the world such as Africa, is in accurately and affordably diagnosing it. An unexpected hero in this battle is the African giant pouched rat.
Diagnosing TB
The most common ways of diagnosing TB are using a ‘smear test’ or a ‘molecular test’. During a smear test a person analyzes a sample of phlegm under a microscope. Phlegm is mucus that the respiratory system uses to protect itself from bacteria and viruses. During a molecular test, a sample of phlegm is tested for the DNA of the TB bacteria. Unfortunately many places do not have access to molecular testing and although the smear test is cost effective it can frequently miss cases where bacteria levels are low. To address this problem, the nonprofit organization APOPO found a new way to identify the disease by using the African giant pouched rat.
How are Rats the Answer?
These “HeroRats” can utilize their “extraordinary sense of smell” to detect TB in people’s phlegm. The HeroRats are trained to detect specific “VOC’s” which are chemical signatures produced exclusively by the TB bacteria. The HeroRats are trained using “positive reinforcement” where trainers teach the rats to associate the scent of TB with tasty treats like mashed bananas, peanuts, and avocado. The time it takes for a HeroRat to be able to distinguish a positive and negative result is 9 months to a year of training. This may seem like a lot of work but once the HeroRats are trained they can produce results at an extremely fast rate. One HeroRat can screen 100 phlegm samples in 20 minutes, whereas it would take a trained lab technician 4 days to achieve the same number using a microscope.
The method for testing involves a rat being placed into a chamber with 10 holes each holding a sample of phlegm. When the rat identifies TB in a sample it is trained to hover for at least 3 seconds over a sample. Once a sample is flagged it is double checked using laboratory methods before notifying a patient.
Real World Results
This method has already produced real world results. In a 2022 study in Tanzania 35,766 patients who showed one of the four symptoms of TB at a health facility were selected and tested for TB using traditional laboratory methods. The patients who tested negative were retested using the HeroRats. The smear test identified 1900 cases as positive but the rats identified an additional 2,029 cases that the initial tests had missed. HeroRats proved particularly effective for vulnerable groups who often have low levels of bacteria that are invisible under microscope such as children and HIV-positive patients. While the effectiveness of the HeroRats is more comparable to the smear test when identifying adults with higher bacteria counts they proved to be 6 times more likely to identify TB in patients with lower levels.
By diagnosing and curing TB it not only cures the patient affected but also prevents the spread of the disease to other people. These HeroRats provide an accurate and affordable alternative method for large scale screening of potentially affected patients. While individuals can help by practicing good hygiene and finishing antibiotic courses, the integration of these trained rats into health screenings is transforming the battle against TB.
Written by Sean Furniss