The story of rats fighting TB, landmines to save human life

Dar es Salaam. They are mostly known for their destructive characteristics, and for that reason rats are generally hated.

Development of science and technology has helped to uncover the other side of the coin--rats belong to the class Mammalia that can be trained to carry out different functions that can benefit human beings.

The functions include disease diagnosis, landmines detection, rescue operations and curbing smuggling.

Under the partnership of Belgian non-governmental organisation Apopo and the Sokoine University of Agriculture (SUA), trained ‘African Pouched Rats’ have saved 17,000 lives in Tanzania that could have been lost from Tuberculosis, the organisations reveal.

These are the people whose specimens for TB testing were pronounced negative in hospital laboratories, but re-testing through the trained rats, the same specimens were found to carry pathogens that can lead to TB.

Respective patients were then subjected to TB treatment, saving them from what could be increased tuberculosis mortality.

Speaking exclusively to The Citizen, the Apopo programme manager for TB Tanzania, Dr Joseph Soka, said the said number includes patients tested from 2007 to date in Tanzania.

“They were detected out of over 600,000 samples brought from hospitals for testing using trained rats after they were found to be TB-negative in the laboratories,” he said.

He said Apopo collaborated with 78 health centres across the country including the Muhimbili National Hospital (MNH), Benjamin Mkapa Hospital in Dodoma, regional referral hospitals of Temeke, Mwananyamala, Amana, Dodoma and Morogoro.

They also include public and private owned dispensaries and healthcare facilities that have the role of providing samples for testing using the new technology.

“Positive and negative TB samples are collected and taken to the ‘African Pouched Rats’ for testing. Some TB-samples that tested negative in hospital laboratories have been detected to have the disease microorganisms,” he said.

“Instead of directly subjecting the patients to TB treatment, rats’ findings are confirmed by laboratory tests. Respective hospitals and healthcare centres are then informed in order to communicate with respective patients,” he added.

But, Health ministry’s permanent secretary Abel Makubi said there was nothing strange for the rats to detect TB from samples that couldn’t be detected in hospital laboratories.

“That is how science operates. Detection of TB and other diseases depends on the technology’s validity. However, there is no equipment globally with a 100 percent detection capacity,” he said.

“Efficiency of technology depends on the time at which the sputum was taken, the amount of bacteria in the sample and manufacturing detection capacity,” Prof Makubi added.

He said the government has been positively collaborating with Apopo in execution of its activities because the organization provided assistance in TB samples verifications.

“I’ve personally visited the Dar es Salaam laboratory. However, securing the World Health Organization (WHO) certification that will establish the technology’s international acceptance was the remaining challenge,” said Prof Makubi. “As the government, we have recommended them. However, WHO has its own procedures of decision making,” he added.

How African Pouched Rats are trained

Speaking to The Citizen, Dr Soka said it takes nine months for African Pouched Rats to graduate.

During training sessions the rats are well cared for by providing them with the best diets, regular exercises, plenty of personal attention, scheduled playtime, regular care from a vet and onsite animal welfare officer.

Socialisation and habituation

He said four weeks old rats are taken from parent African Pouched Rats, noting that at this age, they begin to open eyes and learn to familiarize themselves with surroundings and people.

“They are regularly handled by trained staff. They are also introduced to daily human sounds and smells,” said Dr Soka.

Click training and scent conditioning

According to him, during this time, rats are trained to associate with the sound of a click followed by provision of reward which is usually a tasty food. “Clickers are usually made when rats have successfully identified TB-positive sputum samples. Upon hearing the click, the rat is rewarded,” he said.

Scent discrimination

Dr Soka said at this stage rats are trained to distinguish TB-positive samples from negative specimens, noting that they will be rewarded only after they have identified positive samples, not otherwise.

“Their efficiency needs to be 100 percent. Failure to identify all positive samples could nullify the whole process,” he said.

Multiple sample evaluation

He said in a large testing chamber, rows of 10 samples are placed beneath sniffing holes and that the rats are trained to evaluate a large number of samples.

“At this stage, rats are trained to hold their nose over TB-positive samples for at least three seconds. However, they will pass away the negative samples,” he said.

Rats’ graduation

Dr Soka said TB rats are then evaluated through a strict testing process whereby they are supposed to find all the TB-positive samples and correctly ignore negative specimens. “They are allowed to miss no more than one positive and indicate two or fewer negatives in order to pass the test and graduate,” he said.

TB detection procedures

Dr Soka said rats are nocturnal animals that are inactive during the day, therefore, they are taken to activation chambers equipped with different equipment that could be used for playing, jumping ups and down therefore activating them.

Patients tested at local clinic

He said patients with TB signs and symptoms leave sputum samples for testing by conventional microscopy, noting that in some developing countries the method could identify less than half of actual TB-positive patients.

Sputum sample collection

Dr Soka said after clinical tests, both TB-positive and negative samples are collected and transported to APOPO’s central lab for testing on the same day.

“The samples are then heated deactivate its infection powers trainers and rats,” he said.

TB detection

He said rats smell all the samples and receive rewards for holding noses over a known TB-positive sample for about three seconds therefore increasing accuracy and enthusiasm to find more samples with the disease.

“However, if the rat soars their noses for three seconds over a sample marked negative, then the said sample is labelled suspect,” he said.

Furthermore, he said one rat can check 100 samples in less than 20 minutes, compared to four days that would be required by a lab technician.

Confirmation rat findings

However, Dr Soka said through WHO-endorsed methods, suspect samples are taken for confirmation before informing respective healthcare centres to communicate with respective patients for starting treatment.

Broadening the technology’s scope

Dr Soka said currently, the project is implemented in Tanzania (Dar es Salaam and Morogoro laboratories), Mozambique and Ethiopia.

According to him, Apopo is collaborating with the Health ministry through the National Leprosy and Tuberculosis (NLTP) in establishing a laboratory in Dodoma that could serve neighbouring regions of Singida and Manyara.

“It is important for the office to be established in Dodoma which is experiencing a staggering population growth that could lead to the possibility of TB transmission. Likewise, herders in Manyara Region who consume milk without boiling,” he said.

Dr Soka said Apopo was now doing a feasibility study to identify the plight of TB in Lake Zone regions where they are planning to build a laboratory that will benefit Shinyanga, Simiyu, Kigoma and Kagera regions.

Challenges

According to Dr Soka, Covid-19 outbreak shifted resources and manpower priorities, something that adversely affected accessibility of TB samples for rats testing.

Furthermore, he said stigma prevented TB patients from visiting hospitals and healthcare centres fearing to be related to Covid-19 patients something that further affected the access of sputum for use in APOPO laboratories in Dar es Salaam and Morogoro.

“Transport and transportation challenges during Covid-19 led to the shortage of sputum preservation containers. We were forced to procure 50,000 containers and subsidize healthcare centres in order to enable us to get the sputum,” he said.

He said the disease also claimed the life of some officials and that inflation caused by ongoing war between Russia and Ukraine has adversely affected the organization’s budget.

“Also, the country’s exchange rate has severely dropped with euros plunging from Sh2,600-Sh2,700 to Sh2,300,” he said.

“APOPO is a non-profit making organisation devoted to saving the lives of citizens. But, the government could assist us in different areas. For instance, we are paying about Sh58 million per year for leasing this building from the government,” he lamented.