African Giant Pouched Rats Learn to Diagnose Deadly Disease

Pouched Rat

Story at-a-glance -

  • Not much is known about the African giant pouched rat, a rodent native to Africa that’s about twice the size of an average gerbil. One thing we do know about these critters is they have a keen sense of smell.
  • The non-profit organization APOPO has trained the rats to detect buried land mines around the world. More recently, the organization has been clicker-training rats to detect tuberculosis in human sputum samples.
  • The rats are much more efficient than human lab techs. They can analyze more samples in 10 minutes than a tech can do all day.

By Dr. Becker

Have you ever heard of the African giant pouched rat? It’s about twice the size of a gerbil and not nearly as cute.

The African giant pouched rat, Cricetomys gambianus, is also known as the Gambian giant pouched rat. It is endemic to all of sub-Sahara and Africa. Adult rats grow to over two feet in length and weigh three and a half to four pounds. African pouched rats can live up to eight years in captivity and are docile and friendly to humans.

These rats have very poor vision but an incredibly keen sense of smell. For the last several years, the non-profit organization APOPO has been training the rats to detect buried land mines around the world.

The Rats Are Clicker-Trained for Their Latest Assignment

APOPO’s latest undertaking is training African giant pouched rats in Tanzania to detect tuberculosis in humans, a disease that kills over 1.4 million people each year and is a leading cause of death in Africa.

Diagnosing TB in many parts of Africa is a formidable challenge because traditional methods require specific medical skills. There is a new tool available for detection called “Xpert,” but the machine runs $17,000 and each test costs $10.

To increase the number of TB tests performed, a team of chemists and technicians in Tanzania uses clicker training to teach the rats to detect the disease by sniffing human sputum. The animals are trained at just a few weeks of age to associate clicks with bites of mashed bananas and special pellets of food. Then the technicians link the scent of TB to the food reward.

Once trained, individual rats can detect TB in sputum samples about 66 percent of the time. When two or three rats are put to the test, the detection rate increases to around 80 percent.

According to chemist Negussie Beyene, the rats get better results than many clinicians working in rural Africa do. 

A Rat Can Test More Samples in 10 Minutes Than a Tech Can Do All Day

Currently APOPO has about 32 rats in their TB detection program. They are working at a laboratory in Morogoro, Tanzania, where they are being used to verify microscopy test results.

The laboratory collected over 30,000 sputum samples from clinics and hospitals across the country in 2012. With the rats on the team, they’ve been able to diagnose twice the number of positive results as the clinics alone.

Out of about 1,000 samples collected each week, 20 percent are positive for TB, but only 10 percent are detected through microscopy alone.

The rats are also much faster than the lab techs. They can analyze more samples in 10 minutes than a tech can do all day. One super speedy rat named Harod can clear 10 sputum samples in 20 seconds.

It costs about $8,000 to train and provide care for a scent-detection African giant pouched rat for his lifetime.

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