HeroRATS: African Rats Trained to Sniff Out TB
07/30/2009
Bart Weetjens on HeroRATS: African rats who can detect TB faster than humans
Training African giant pouched rats to detect pulmonary tuberculosis may sound like an extra-ordinary idea. In reality, it is a novel and alternative tool to enhance case detection in resource limited settings, at higher speed, smaller cost, and lower levels of skills in the operators. Moreover, this approach doesn't require any hi-tech equipment, or expensive reagents.
It began when the rats - HeroRATS - were trained by the organization APOPO to detect landmines. After several years with a proven record for successful demining, HeroRATS now also addresses another humanitarian detection application: TB diagnosis.
In ancient history, pulmonary TB has been diagnosed through interpretation of the volatile biomarkers exuding from human sputa. The ancient Chinese and Greek used a hot stone or a flame to burn the sputum of suspected patients and interpret the odour in the fume. Recently, plural research efforts for better TB diagnostic also pursue vapour detection, through the development of electronic noses and other tools, either in sputa or in breath.
In Tanzania, a country without landmines, but with a high TB burden, APOPO saw the potential of using rats to diagnose TB, and trained a small group of animals on the discrimination of TB positive sputa versus TB negative sputa. Whereas a trained lab technician can process a maximum of 40 sputum samples in a day, a HeroRAT can discriminate the same amount of samples in 7 minutes only! And HeroRATS can do this pretty reliably: in real world circumstances, a HeroRAT scent detection setup can diagnose pulmonary TB at 86 percent sensitivity and 89 percent specificity, or an overall reliability of 87 percent, compared to traditional sputum smear microscopy which reaches an alarming overall reliability of only 37 percent in Tanzania.
How it works: The rat sniffs a series of holes, under which human sputum samples are lined up for evaluation. They pinpoint the samples which contain TB bacteria by scratching the floor. They are rewarded with a click and a subsequent food treat.
Between January and December 2008, APOPO collected more than 22,000 sputum samples from nearly 8,000 suspected patients in 4 public health centers in Dar Es Salaam, Tanzania, and analyzed these samples by means of trained HeroRATS. About 1,200 patients (or 15 percent) were found positive by smear microscopy in the health centers, and at APOPO another 344 patients were identified by the HeroRATS (afterwards confirmed by means a second smear microscopic test). By combining HeroRATS - featuring a higher sensitivity - and smear microscopy - featuring a higher specificity - APOPO was able to enhance case detection in the four collaborating health centers by almost 30 percent.
These very promising results motivate APOPO to further HeroRATS research into medical diagnostic applications. Very little is yet known about vapour detection of pulmonary TB, and APOPO's work can make a great contribution to this realm of investigation. Diagnosis of TB/HIV co-infection may be one of the market niches for HeroRATS. It is well documented that HIV positives have tendency to produce negative smears. APOPO is in the process of obtaining ethical clearance in Tanzania to investigate the co-infection of HIV and TB in those patients that were initially missed by microscopy but later retrieved by HeroRATS.
APOPO now has 25 animals trained on TB discrimination, a prototype scent detection setup in which the animals work, and operational procedures for the use of HeroRATS. A system has been installed to enable tracing of suspected patients by means of mobile phone numbers. However functional, it is not yet a technology, but rather ‘arts and crafts' at this stage. In order to scale the tool, APOPO will standardize processes, optimize the samples (including transport and storage, and also look into the possibilities of utilizing breath samples), semi-automate the scent detection setup and improve the data collection and management, and try out the use of rats as a first line screening tool, while furthering the basic science on volatile organic compounds characterizing TB, in co-operation with the Max Planck Institute in Berlin.
Bart Weetjens is the founder of APOPO.
I would definitely second that, Paula!
— Hal Campbell on 2009-08-19
Excellent example of historical interest combined with lateral thinking and a determination to follow through. Sounds very promising. Congratulations.
— Maria Paalman on 2009-08-21
Very interesting.The possibilities of detecting TB by means of volatile scent from human sputum with relative high sensitivity will obviously help in the resource poor settings.In country like India. it will open an alternative avenue for diagnosing TB, very promising initiative no doubt about that.
— Dr.Silajit Sarkar on 2009-08-22
It is indeed a great help in detecting TB in the world. It provides understanding the usefulness of animals for human health. Our concerns should be not to exploit these innocent animals for human use. However, it is best example of appropriate technology and need for harmoneous relationship on Earth.
— Dr. J. Kishore on 2009-08-22
I think this is very good news.We should quickly pursue its use.
— DR.Edward E.Moshi on 2009-09-03
Amazing! Ability to detect TB cases through sputum microscopy is affected by the skill and morale of the Laboratory technician and sensitivity/specificity of the test itself. Under such circumstances use of trained animals to detect cases with a reliability of 87% without any harm to the animal is a milestone in the history of fight against TB. More detection will enable us to reduce transmission drastically and rapidly.
— Dr.Sadhu Charan Panda on 2009-09-05
Dear all,
Please do not forget that everybody can support the work of these HeroRats by an adoption of a HeroRat for 5 EUR/month or by a donation. More information you will find under http://www.herorat.org or http://www.apopo.org.
An adoption would be an excellent present for friends and/or family! I have adopted 6 herorats as presents for others this christmas and also one for myself. Updates and pics of the adopted HeroRats now come regularly into my mailbox. It is also great fun :-)!! The HeroRat-Team is definitely the best & friendliest I have ever found!!
— Tina on 2010-01-04
this is indeed a very good news. A common problem faced by programme managers of TB is the demand for incentives by microscopists almost always. TB microscopists are often overworked and inadequate in numbers. These wonderrats could be the future of TB control considering present challenges. Lets pursue these innovation for to improve our TB control….
— Dr Stephen John on 2010-03-15