Abstract
Giant African pouched rats previously have detected tuberculosis (TB) in human sputum samples in which the presence of TB was not initially detected by smear microscopy. Operant conditioning principles were used to train these rats to indicate TB-positive samples. In 2010, rats trained in this way evaluated 26,665 sputum samples from 12,329 patients. Microscopy performed at DOTS centers found 1,671 (13.6%) of these patients to be TB-positive. Detection rats identified 716 additional TB-positive patients, a 42.8% increase in new-case detection. These previously unreported data, which extend to over 20,000 the number of patients evaluated by pouched rats in simulated second-line screening, suggest that the rats can be highly valuable in that capacity.
Highlights
According to the World Health Organization, about one-third of the world’s population is currently infected with the Mycobacterium tuberculosis, which causes tuberculosis (TB), and an estimated 1.7 million people died from TB in 2009
An initial proof-of-principle study suggested that the rats can detect TB-positive sputum samples quickly and more accurately than microscopy [4] and in 2009 researchers reported that scent detection rats increased new TB-positive patient findings by 31% over microscopy alone [5]
A recent study, involving 10,523 patients from Direct Observation of Treatment Short-Course (DOTS) centers in Dar es Salaam, Tanzania showed that use of the rats in simulated second-line screening during 2009 increased case detections by 44%, from 1,403 to 2,023 [6]
Summary
According to the World Health Organization, about one-third of the world’s population is currently infected with the Mycobacterium tuberculosis, which causes tuberculosis (TB), and an estimated 1.7 million people died from TB in 2009. The most common method for identifying TB in East Africa is sputum smear microscopy This technique, though relatively inexpensive, is timeconsuming and fails to detect a substantial number of TB-positive cases when large numbers of samples are analyzed [2,3]. An initial proof-of-principle study suggested that the rats can detect TB-positive sputum samples quickly and more accurately than microscopy [4] and in 2009 researchers reported that scent detection rats increased new TB-positive patient findings by 31% over microscopy alone [5]. The importance of the present study is that it expands to over 20,000 the number of patients evaluated by the rats in simulated second-line screening and evaluates whether results comparable to those previously reported [6] can be replicated under conditions somewhat different from those of the original investigation. The present study is a systematic replication and extension of the initial one
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