Rats vital in curbing spread of TB

Almost 5,000 people die from tuberculosis (TB) every day and drug-resistant TB is spreading quickly to alarming levels. In sub-Saharan countries, fewer than 50% of existing TB cases are detected. Left untreated, a patient with active TB can infect an average of 10 to 15 additional people each year. Enter APOPO’s TB detection rats: already, these rats have potentially prevented over 20,000 new cases of TB.

APOPO's TB detection program continues to expand, with more than 2,000 patients identified as TB-positive only through second-line screening by our rats. In 2010, we constructed a new building at our TB Detection Center which provides much needed space for offices, a meeting room, and a dedicated data management area. Remodeling of the original lab extended the animal colony, and improved the behavioral testing areas. APOPO also purchased new fluorescent microscopes (FMs) and a Cepheid GeneXpert, advanced diagnostic equipment which is now being used to analyze smear slides and further our research. The FMs allow for greater accuracy than the light microscopes previously used, while the GeneXpert provides a tool for verifying the presence in TB in samples evaluated as TB-positive by the rats.

In 2010, HeroRATs evaluated 26,665 sputum samples from 12,347 patients, initially screened by smear microscopy at Direct Observation of Treatment, Short Course (DOTS) Centers. The DOTS Centers identified 1,671 of these patients (13.5% of the total) as TB-positive. Analysis of these sputum samples by the rats, followed by confirmatory microscopy conducted at APOPO, identified an additional 716 patients as TB-positive that were initially missed by the DOTS centers. Thus, the use of rats in simulated second-line screening increased the new-case detection rate by approximately 43%.

This increase is similar to that obtained in 2009, when use of the rats increased new-case detection by 44%. The 2009 findings formed the basis of a journal article, entitled “Using Giant African Pouched Rats to Detect Tuberculosis in Human Sputum Samples: 2009 Findings” that appeared in the American Journal of Tropical Medicine and Hygiene (AJTMR) in 2010. The article generated substantial media attention. A second article, “Tuberculosis detection by giant African pouched rats (Cricetomys gambianus)”, which summarizes APOPO’s TB detection activities, was also accepted for publication in The Behavior Analyst and will be published in 2011.

In order to systematize APOPO’s TB detection activities, APOPO formulated and began implementation of a three-year research plan in 2010. It outlines studies that provide a compelling comparison of rats’ evaluations to the results of culturing and GeneXpert, develops strategies for using the rats in first-line screening, and optimizes behavioral procedures.