APOPO Tuberculosis Detection

What is Tuberculosis?

Tuberculosis (TB) is still the world’s most deadly infectious disease and a global Stop TB Partnership has been developed  to try and stamp out the disease once and for all. The disease is both treatable and preventable, and yet worldwide it kills approximately 3 people per minute (over 1.5 million people per year). TB has almost been eradicated in the “Western world”, and so the disease is increasingly associated with poverty, where access to reliable healthcare can be very difficult and there are many other diseases which increase the danger of having TB. There is a global aim to End TB by 2030 (supported by the WHO End TB Strategy and UN Sustainable Development Goal 3) and a significant part of the challenge is in developing fast, cheap and effective detection measures so that sufferers can go into treatment programmes before they infect many other people. 

WHO TB Facts estimate that an untreated active case of TB is likely to lead to 10-15 more cases as the person infects other people around them. TB is caused by bacteria called Mycobacterium tuberculosis that most often affect the lungs. The disease spreads through coughs and sneezes, and so an infected person is likely to infect those they come into close contact with (family and colleagues or classmates). It can take many months or years for any symptoms to develop (an active case of TB) and the symptoms, which include a cough, fever, night sweats or weight loss, can be mild or mistaken for something else for many months, leading to delays in seeking care. For this reason, active campaigns to raise awareness of the symptoms and an extensive programme of routine testing can be the key in driving down the number of new cases of TB in a region. The treatment programme is 

Over 95% of cases and deaths are in the “developing world”. There are 30 countries in the world that are classed as High TB Burden; these countries accounted for 87% of all the TB cases recorded in 2018.

The United States Centers for Disease Control and Prevention (CDC) website has information on Tuberculosis, from the perspective of managing TB infections within the US (just over 9,000 reported cases of TB in 2018).

Tuberculosis diagnosis and treatment

Tuberculosis viewed under a microscope

 An extraordinary number of cases are missed using the current widely available detection method – smear microscopy, where a trained laboratory technician examines a sample under a microscope, looking out for the rod-shaped TB bacteria (learn more about looking for TB using a microscope in this handbook). The thing is, it’s not always easy to spot when there aren’t many TB bacteria in a sample, but the cost of missing any TB patients could be high. There are high-tech methods that have been developed and have been increasing in use since 2010 but they are still comparatively expensive and very hard to access in many places in the world. A rapid test can be performed using Xpert MTB/RIF, which can give a diagnosis in 2 hours. Tuberculosis is particularly difficult to diagnose in children, at least partly due to the difficulty in getting good quality samples of sputum coughed up from the lungs.

TB treatment is a challenge in poor communities – it requires a six-month period of treatment with antimicrobial drugs. As with antibiotics, it is absolutely essential to undergo the full 6-month treatment to ensure that all traces of the disease have gone, otherwise patients would increase the risk of the development of drug-resistant strains of the disease. 

Ridding the World of TB

UN Sustainable Development Goal 3 is to Ensure healthy lives and promote well-being for all at all ages. This includes dealing with infectious diseases (including malaria and tuberculosis), childbirth and childhood, non-infectious diseases, and access to healthcare. 

Stop TB Partnership – established in 2001 with an amazingly diverse group over 1,700 partners working in over 100 countries. There are 7 working groups that are approaching the problem from different angles and there are interim goals for 2020 and 2025 with the aim to end the epidemic by 2030. It is estimated that 58 million lives have been saved between 2000 and 2018 through TB diagnosis and treatment

This is where APOPO comes in…

So APOPO have developed a stunningly quick method of checking samples using highly-trained rats who signal to the handler when they are presented a sample which contains TB. LINK TO APOPO TRAINING

Carolina, a trained TB detection rat, is moved into her glass office for her 20-minute shift. Along the floor are a row of 10 small hatches. Her handler fits a metal bar holding 10 sample pots into its housing beneath the hatches and then, one by one, a handler moves along opening and closing the hatches in turn, so that Carolina can carefully sniff the sample pot before moving on to the next one. If Carolina detects that the sample contains any of the TB disease, she pauses and signals to the handlers that she has found a positive sample. The handler team makes a note of which sample she has warned them about and then they carry on, row after row, for up to 20 minutes. During this time, Carolina could check up to 100 samples. 

To make sure Carolina’s skills are kept sharp, some of the samples in the stack are known to be positive for TB, so if Carolina spots these “control samples”, she hears a clicker and she runs to the end hatch to get her reward of peanut and banana paste then she gets straight back to work. At the end of her shift, Carolina enjoys a lovely cuddle with her handler before going back home to relax until dinner time.

The Dar es Salaam and Morogoro TB Facilities receive thousands of samples every month from over 60 clinics in the region that have already been checked for TB using smear microscopy. Almost all of the samples (except the control samples) have been declared TB Negative (no TB), however, when the rats check the samples, they find many cases of TB that would have been missed if the initial results alone had been relied upon. The number of new cases identified each month by the team of TB detection rats varies greatly, but in September 2019, a team of 9 rats identified an additional 104 cases of TB in samples that had been declared “TB Negative” by the first detection method. 

And the rats are so quick! Each sample has to be checked by more than one rat, to give the best possible chance of detecting a new case, and every “rat-positive” sample is then closely checked by a laboratory technician, leading to the final “TB Positive” or “TB Negative” verdict. Results are then transmitted back to the clinics as soon as possible so that the patient can be notified that they must begin treatment. This has hugely increased the number of TB patients beginning the six-month treatment programmes – potentially drastically reducing the number of people that go on to become infected in the community.

The method is so fast and effective that APOPO can conduct mass population screening – where many people within an “at risk” community provide samples even if they have no symptoms – this can help to catch an outbreak before it causes suffering and spreads through the community.