Guest Articles

April 7

Kyle Poplin

More Giant Rats On the Way. And That’s a Good Thing.

According to the World Health Organization (WHO), 1.5 million people died from TB in 2014, 95 percent of them in low- and middle-income countries. APOPO trains African giant pouched rats to sniff out landmines and tuberculosis (TB), a top infectious disease killer worldwide – even though TB’s curable and preventable. The rats are currently being used to screen for TB in crowded prisons in Tanzania and Mozambique, and as Charlie Richter, U.S. director of APOPO, explains below, there are plans to expand the program. He spoke with NextBillion Health Care Editor Kyle Poplin. 


Kyle Poplin: What is APOPO and how and when did it get involved in using rats to detect landmines and tuberculosis?

Charlie Richter: APOPO is a social enterprise that researches, develops and implements detection rats technology for humanitarian purposes such as mine action and tuberculosis detection. APOPO is a Belgian NGO, with headquarters in Tanzania and operations in Mozambique, Thailand, Angola and Cambodia. 

The original idea to use rodents for detecting landmines emerged in research studies in the mid-1970s. Two decades later, APOPO founder Bart Weetjens, a rat-lover himself, was reading about the use of gerbils as scent detectors. Mr. Weetjens knew that rats, in particular African giant pouched rats, possessed a keen sense of smell and were prevalent in parts of the world with large quantities of landmines. And thus, in 1998 APOPO was born and began research with “HeroRATs” the following year.

After years of success in landmine detection, APOPO began testing their HeroRATs to address other humanitarian challenges in Africa. In 2002, as TB surged across the continent, APOPO tested its HeroRATs to sniff out positive TB sputum samples from hospitals in Morogoro, Tanzania.


KP: How are the African pouched rats trained, and how old are they when they start? Is it difficult to train them? Expensive? How many rats have been trained? How long do African pouched rats live? Does APOPO have “rat whisperers” who are especially good at training them?

CR: Training begins with socialization shortly after birth. Once the rats open their eyes at the age of four weeks, they begin to interact with people and become sensitized to the various stimuli of a lab. To hone their ability to detect the mycobacteria (that causes TB), technicians use “clicker” training to provide positive reinforcement and scent conditioning to establish an association between positive sputum samples and a food reward.

Next, lab technicians begin to give the HeroRATs sputum samples to determine between positive and negative. The rats are trained to pause for roughly three to five seconds over positive samples. Over time, the samples gradually increase in number until the rats can distinguish between 10 samples at a time. In order to pass internal accreditation the rats must be able to correctly identify all positive samples.

Photo by Briana Marie for APOPO.

Photo by Briana Marie for APOPO

It takes roughly nine months to fully train a HeroRAT, and they perform their job diligently for approximately four to six years before they live out their remaining years in rat retirement. African giant pouched rats typically live up to eight years.

APOPO has accredited 50 TB rats so far and maintains a research and training staff of 33 individuals. The variable costs of training one rat are less than $2,000 and if APOPO was training at capacity, would be under $1,000.

Staffer Albert Carol is one of these “rat whisperers” who is charged with socializing all the facility’s baby rats, exposes them to people, tastes, smells – and a variety of situations. Albert explains: “During one week, I will be taking the pups outside the kennels for about 20 minutes every day. I let them smell different odours like tea, coffee and oil, they get to hear different sounds like a ringing phone and human voices and they get to wander around on different surfaces such as sand, wood, grass and concrete. I make sure they are exposed to all kinds of smells, textures and sounds, but especially to being handled by people. Every individual pup gets plenty of attention and learns to be held and carried by the trainers.”


KP: What’s the traditional method to screen for TB and how long does it take?

CR: Traditional methods of screening for TB in developing countries rely on smear microscopy, a century-old technology. While relatively cheap to conduct the test, smear microscopy only detects 60 percent of all cases. In some of the worst affected regions of the world, especially where HIV is prevalent, these rates drop off to a range of 20 to 40 percent due to complications in detecting the mycobacteria when HIV is present.

To ensure that those suspected of having TB are correctly diagnosed, these samples are then confirmed by LED microscopy or Xpert MTB/RIF, the WHO-recommended technology for identifying suspected cases of TB. The conventional methods of microscopy may take a lab technician two days or more to test 100 sputum samples, what a HeroRat can identify in just 20 minutes.


KP: How do the rats find TB – what samples are they provided – and how quickly and often can they do the screening? How accurate are they?

CR: The rats are able to detect the mycobacteria found in TB-positive samples of sputum. They can test up to 100 samples in 20 minutes, with a roughly 70 percent accuracy rate.

The HeroRAT technology is an effective screening tool because it reduces time and cost by referring fewer samples for lengthy smear or Xpert testing. To date, HeroRATs have screened over 340,000 TB samples, resulting in a 45 percent increase in TB detection at partner clinics. Prior to the use of the HeroRATs, these clinics would have incorrectly diagnosed 50 percent of symptomatic TB-positive patients as TB-negative.


KP: USAID’s Development Innovation Ventures recently awarded APOPO a grant to scale up its testing. How much was the grant and what will it be used for? What other organizations have helped fund or are involved in the project? Are there plans to make the program self-sustaining and, if so, how might that work?

CR: USAID’s Development Innovation Ventures awarded APOPO an $80,000 grant to test and scale its unique TB detection method in Mozambique and Tanzania. The grant will inform a diagnostic accuracy study of the technology in high-risk populations, such as prisons, and will add rigorous scientific evidence toward WHO endorsement. DIV is an open innovation fund at USAID that sources, supports and scales breakthrough solutions to global development challenges.

APOPO has also received some funding from European foundations for active case finding research among sugar plantation workers in Mozambique. Its routine re-screening program, which has existed for over seven years, is funded by several European development agencies and private foundations. APOPO also secured a major grant from the Skoll Foundation in Palo Alto to expand its routine re-screening program to Ethiopia, pending successful NGO registration in the country.

In the short- and mid-term, APOPO plans to sustain the project through partnerships with major TB project implementers and continued direct funding from various foundations and development agencies. APOPO also has a public fundraising program wherein individuals can virtually adopt a HeroRAT. This revenue stream gives us a safety net should there be gaps in donor funds.

Within three years, APOPO hopes to convince WHO to endorse the technology for both active case finding and routine rescreening in high-burden megacities. If APOPO is able to get this endorsement, it will work proactively with governments and major implementers to access Global Fund money for its programs.


KP: Where might the testing be expanded in the future?

CR: Tanzania and Mozambique are two of the highest TB-burdened countries in the world, with estimates of 150,000 cases in Mozambique and 270,000 cases in Tanzania. Since TB is a “disease of poverty” that often results in economic challenges for entire households and only half of the patients with active TB are diagnosed, reaching the greater population is essential.

APOPO hopes to roll out its TB program in at least six countries by 2020. Ethiopia, Bangladesh, India, Cambodia, Kenya and the Democratic Republic of Congo are all under consideration for future programs. Raising the funding and establishing the partnerships needed to succeed in these areas are a much bigger challenge to scaling than rat development capacity.


KP: Are other animals capable of the same screening?

CR: Mycobacteria found in TB emits organic compounds detected by rats through their enhanced sense of smell. Though not part of the APOPO program, canines would likely be able to detect TB at similar accuracy levels to rats. However, rats are much cheaper to train and maintain in a controlled lab environment, and they can move much more quickly from sample to sample than dogs can. APOPO also hopes to experiment with HeroRATs’ ability to do cancer detection in the future.


KP: What are the advantages of early detection of TB?

CR: Every year, there are 9 million new cases of TB, and 1.5 million people die, most of whom live in developing countries. TB flourishes in crowded environments such as prisons, packed working conditions and slum dwellings. Left untreated, a person with TB will infect as many as 15 others with the disease, rapidly spreading TB through high-density populations.

People with compromised immune systems due to malnutrition or other diseases are also especially vulnerable to TB. The good news, however, is that when tested early and properly diagnosed and treated, the prognosis is highly favorable. With early detection from APOPO, an individual can receive lifesaving treatment earlier and halt further spread of the disease.


KP: After a positive test, what are the next steps? Is APOPO involved in that process?

CR: After positive sampling by the HeroRATs, a sputum sample is then confirmed through LED microscopy or Xpert testing performed at health centers. The health centers then track down patients to notify them of their TB status and, when necessary, begin treatment for the disease.

APOPO implemented a new operational strategy in 2015, allowing APOPO to deliver test results to clinics in Maputo, Mozambique, in less than 24 hours. When patients go to pick up the results of their smear microscopy performed at clinic laboratories they also receive their APOPO test results. The aim is to reduce patient tracking and increase treatment initiation.

Through collaboration with community health centers, both in the city of Maputo and around the country, TB treatment commences quicker than ever before.


Top photo by Maarten Boersema for APOPO. Visit APOPO on Facebook.



Kyle Poplin

Health Care, Social Enterprise
Base of the Pyramid, healthcare technology, infectious diseases, social enterprise