Not only can these rats detect tuberculosis, but they also seem much more effective than the tests currently used by doctors to detect the disease in children.
Tuberculosis is a contagious disease that usually attacks the lungs, but sometimes also other parts of the body such as kidneys, ganglia and bones. It is one of the top ten causes of death on the planet. Every day, nearly 5,000 people die from this infectious disease, considered the deadliest in the world. It is also difficult to detect. Current pediatric TB tests have a sensitivity of only 30-40%. In contrast, a trained rat would be 40% more effective, according to an article published April 4 in the journal Pediatric Research.
Of the 1.3 million people who died of TB in 2016, 130,000 were children from sub-Saharan Africa. Difficult to screen in these areas, because young children have difficulty producing enough sputum (a mixture of mucus and saliva) to produce a sample. Researchers based in Tanzania and Mozambique then decided to look at rats, after realizing that some lung diseases had strong and identifiable odors.
They trained African giant rats (Cricetomys ansorgei) to sniff out certain compounds produced by tuberculosis, including the bacterium Mycobacterium tuberculosis. The doctors then took the rodents to local hospitals and collected saliva samples from patients for some tests.
Note that the training technique here is similar to that used to teach rats to detect vapors emitted by land explosives. In the case of tuberculosis, when a rat points to a potentially infected sample, it is analyzed using concentrated microscopy techniques approved by the WHO to confirm a positive diagnosis.
The researchers report in the paper that tuberculosis tests detected the disease in 34 children aged 1 to 5 years, and that the rats detected an additional 23 cases. These were all confirmed later by repeating the sputum test, several times in some cases. Similarly, when existing tests detected 94 cases of tuberculosis in children aged 6 to 10 years, the rats detected 35 more. In adolescents, the existing test revealed 775 cases, to which are added 177 additional cases detected by rodents. Finally, among adults, existing tests detected 7,448 cases. The rats detected an additional 2,510.
In other words, rodents have proven to be much more effective than existing tests in every age group. The study authors also note that more research will be needed to determine the extent to which rats’ noses are sensible to tuberculosis.