Say “rats and disease” and your first thought is probably bubonic plague, rats as the carriers of deadly illnesses. However, now African giant pouched rats (Cricetomys gambianus), weighing in at 10 to 15 pounds, are helping to fight tuberculosis in Tanzania:.The rats’ sensitive noses are able to detect TB in human phlegm by its smell.
Two years ago, Alan Poling, a psychology professor at Western Michigan University, reported that he and his colleagues had successfully trained the giant rats to identify the scent of TB in sputum samples. Starting when they were a few weeks old, rats were trained using Pavlovian conditioning to associate a click sound with a small bite of mashed banana and a special food pellet. Some were then able to learn to detect the tuberculosis bacilli in human phlegm with as high as an 86.6 percent accuracy rate; they were even better (93 percent accuracy) at detecting the absence of the bacteria. When compared to detection via using a microscope, the rats picked up 44 percent more positive cases.
Human experts were initially wary about using rats to detect disease, rather than the usual equipment and techniques that have become de facto in modern Western medicine. While describing their tuberculosis-detecting skills as “amazing,” Neil W. Schluger, a professor of medicine at Columbia University, issued a number of caveats to the New York Times in 2011:
…but even if you accept that it worked within their lab, are they still good at it a year later? Do they all have to be trained by the same person? How do they have to be cared for? If you change their cage or their bedding, does it still work?
Two years later, chemist Negussie Beyene and a team of workers from APOPO (which also uses the rats to detect land mines) are using Poling’s techniques to train rats to detect TB in Tanzania, where thousands die every year from the disease.
As NPR reports, about 32 rats have been trained at a small laboratory in the city of Mongoro in Tanzania. The rats work as a “second-line screening system there to verify results from current microscopy tests” conducted in clinics in rural Africa. Microscopy from such clinics is only about 30 to 40 percent accurate and misses nearly half of the cases of tuberculosis.
Thanks to the rats, health workers have been able to detect about twice as many cases of tuberculosis. The rats also work far faster than a human can: one rat can analyze more samples in ten minutes than a lab technician can in an entire day. A rat whose name is Harod can evaluate ten samples in just 20 seconds.
Here’a giant rat at work detecting TB:
The rats do have their limits. They are unable to detect a drug-resistant strain of tuberculosis. A $17,000 machine, Xpert, is needed in this case.
The giant rats have a lifetime of about eight years; it costs some $7,800 to train and house them for all that time. While those of us who live in the Western world probably won’t be seeing any whiskered “assistants” in our local clinics soon, the giant rats could indeed be a “good fit for hospitals and clinics in the developing world, where resources and two-legged medical workers are harder to come by,” as NPR notes.
Poling has noted that, aside from their long and scaly tails, the giant rats would be downright “loveable.” As he told the New York Times: ”They’re handsome animals, they follow you around, come when you call them.” Rats probably won’t be everyone’s favorite animal but some are certainly something more than pests.
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Photo via U.S. Army Materiel Command/Flickr
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