“Detection rats technology” consists of equipment, training methods and operational procedures in which trained rats detect Tuberculosis. One TB evaluation unit exists of a semi-automated cage, featuring 10 holes and an automated food pellet dispenser. The holes are covered with lids and under the holes 10 sputum samples are presented for odor discrimination by rats. The lids are uncovered one by one and the animals sniff hole per hole for positive targets. Every hole is equipped with a laser beam, broken by the nose of the rat. A rat only needs a few hundreds of a second to discriminate the target odor. In case of a negative sample the rat immediately moves on to the next sample. Positive samples are indicated by keeping their nose fixed in the sniffer hole for at least 3 seconds, which is registered in a database. Known positives are inserted to allow reinforcement of indication behavior. At 3 seconds indication of known positive samples, the animals hear a click sound and they receive a food reward. Indications of a suspect sample, are not reinforced but noted down. Rat detected suspect samples are re-tested on the presence of TB using concentrated smear and LED microscopy.
There are approximately 9 million new cases of TB per year and 1.5 million people died from TB in 2014. Left untreated, a person with active TB can infect 10-15 new people each year. Therefore a fast and accurate diagnostic technology is needed. In many developing countries, TB is still detected through microscopy. The method can be precise but is slow and between 20-80 % of positives can be missed. The scent technology relieves high TB incidence, low income countries of their dependence on the expensive and often unavailable TB diagnostics as it is a fast, accurate and cost-effective screening tool. The rats evaluate 100 sputum samples within 20 minutes; this would take a lab technician more than 2 days using microscopy. So far more than 9,700 TB patients who were initially missed by means of microscopy were diagnosed, thus preventing 36,000 potential infections. APOPO has managed to increase the TB case detection rate by an average of 40 %.
Following are the cost figures for the TB Detection Technology:
5 €: Keeps one rat in training, food and healthcare for a month
60 €: Keeps one rat in training, food and healthcare for a year
6000 €: Fully trains a HeroRAT from birth to operational stage (9 months).
Once trained, due to its speed, its costs per detection are very low and reduce even further the more samples its tests. APOPO are currently carrying out a cost-efficiency study to accurately support this.
10,000 €: cost of an automated cage
150,000 €: cost of a mobile cage
190,000 €: total budget of APOPO TB detection in Tanzania for one year (as of 2013)
140,000 €: total budget of APOPO TB detection in Mozambique for one year (as of 2013)
The scent Technology can be replicated elsewhere while APOPO is able to provide:
- Standard Operating Procedures
- automated training and evaluation system with minimum human training requierements
- training for animal trainers and system operators
- pre-trained rats
- QA support
Stage of development: Produced in serial production
The semi- automated cage, constructed of stainless steel and clear plastic, is 205 cm long, 55 cm wide, and 55 cm high. A commercially available pellet dispenser is located at one end of the cage.
The cage floor contains 10 sniffer holes 2.5 cm in diameter located symmetrically along the centerline of the long axis. A hollow metal sample bar with holes allows for the presentation of sputum samples. Electronic sources direct a photocell beam pass below each hole and beam detectors allow accurate detection of how long each beam is broken. Information from the photocell detectors is conveyed to a computer equipped with APOPO software APOPO for recording and analyzing data.
Used by: Mozambique, Tanzania