man’s new best friend

When you think of the heroes of the animal world, rats don’t usually come to mind. Oh, sure, they’ve been used in countless experiments that have greatly enhanced scientific knowledge, but they’re not working right by our side like dogs, for example, leading the blind and sniffing out explosives. Well, perhaps we don’t have guide rats just yet, but a Belgian research organization in Tanzania has successfully used giant pouched rats (Cricetomys gambianus) to sniff out land mines, and the same rat researchers are now training them to detect tuberculosis in humans. New Scientist reports that preliminary tests suggest the rats could test as many as 150 saliva samples in 30 minutes, compared to a human using a microscope, who can only test 20 samples in a day. The researchers use reward-based training to sensitize the giant rats (which can grow to the size of housecats) to the smell of the TB bacteria in human saliva samples. The rats are trained to stop in front of a sample with the target smell, and then are rewarded with bananas and peanuts. So far, using 10,000 samples, the rats have a 77 percent accuracy rate in identifying infected samples, compared to a 95 percent accuracy rate with a microscope. Bart Weetjens, the director of the rat program, hopes that by using three or four rats on each sample, the accuracy rate will be increased.

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 12/23/2003.