Some animals, such as dogs, are well renowned for having keen senses that enable them to pick up on a variety of environmental cues that are imperceptible to people.
People have used them for a variety of purposes, including sniffing out narcotics, explosives, and a wide range of other items.
This is in addition to the fact that they are quite receptive to training.
But one more recent and very exciting area of research in which animals are being used is disease detection or, more specifically, cancer detection.
Dogs are far from the only animals showing promise in this area.
Here are ten animals that might be able to sniff out diseases in humans.
In 2021, Korean researchers released a report demonstrating that trained rats could detect toluene, an odour-producing substance that can signal the presence of lung cancer.
You might be wondering how rats can convey what they smell to humans, and the answer is a little strange: the researchers trained the rats to leap onto a floating ledge whenever they smelled toluene.
To make the study more realistic, the rats were not merely given samples of toluene followed by a series of different odours.
They were shown genuine human breath samples that had been gathered by individuals inhaling them into plastic bags and then sealing them.
The scientists later contaminated some of these samples with toluene.
After over a thousand tests, the rats achieved around 82% accuracy in detecting the toluene.
In an unusual—if not plain bizarre—experiment, researchers in the United States sought to see if pigeons could diagnose breast cancer from photos.
Surprisingly, they performed exactly as well as humans!
They accomplished this despite having a brain the size of a fingernail.
Their minds, on the other hand, are pretty strong, especially when it comes to imagery.
They can remember up to 1,800 pictures and recognize persons, facial expressions, and even letters of the alphabet.
Pigeons in cancer research were trained to recognize microscope photographs of malignant and non-cancerous cells, with correct answers rewarded.
When presented with previously unknown photos, they were able to use what they had learned and accurately identify between the images, even when the images were zoomed in or out or discoloured.
It is hoped that the pigeons will aid in the validation of future image-based cancer detection systems.
Okay, so man's best buddy has to make the list someplace.
With a sense of smell that is thought to be 10,000 to 100,000 times greater than ours, it is not surprising that dogs can detect cancer.
Dogs, like ants and bees which will still be mentioned in this list, may detect cancer in ejected materials such as breath and urine.
Furthermore, they can detect cancer while it is still in situ, indicating that it has not spread from the original site of origin.
This is fantastic news since early identification is critical because cancer is far more difficult to cure once it has spread.
Dogs have been trained to detect cancer in breath, plasma, urine, and saliva, and it takes around 300 samples for them to acquire the scent and apply it to fresh, unseen samples.
While some groups employ dogs to detect cancer directly, other researchers are researching their abilities to help design a mechanical nose that would detect cancer in the same way while leaving the dogs alone.
Not only mammals, but even insects, may be capable of assisting humans in the diagnosis of dangerous diseases.
Bees are said to have a great sense of smell that can detect even a few molecules of material in a room, and they have already been used to identify illnesses such as tuberculosis and diabetes.
Furthermore, they can be trained much faster than animals such as dogs.
Their antennas enable them to detect individual odours within a mixture of concurrent aromas, as would be the situation with human breath samples.
Susana Soares, a Portuguese product designer, was working on her Master's degree when she created "Bee's," an elegant glass device that allows people to breathe safely into a chamber containing bees that have been trained with a sugar reward to respond to the detection of certain chemicals.
Ants, like bees, have incredibly sensitive antennae that allow them to detect chemicals that humans cannot detect.
Specific chemicals released by cancerous tumours, as we now know, can have distinct odours.
However, breath isn't the only body discharge where these compounds may be found.
The chemicals also exist in urine, and scientists discovered in 2023 that ants were quite precise in detecting these molecules in mouse pee.
Ants may offer a less expensive and less intrusive method of early cancer detection.
But how can one teach ants to detect the presence of chemicals?
They, like the other animals on this list, were trained using rewards.
It was sugar water in this situation.
When the researchers stopped providing the ants with sugar water, the ants lingered a little longer in the presence of the carcinogenic substances in the urine samples because they were anticipating their reward.
The worms used in this study are common roundworms, which are significantly smaller than the mud-eating earthworms you may find in your yard, measuring only 1mm in length.
Roundworms may be less interested in muck, but it appears that they are quite interested in cancer cells, particularly when hungry.
In the experiment, Korean scientists placed 50 worms on microscope slides among healthy human cells and malignant cells. Approximately 70% of the worms wiggled their way to the cancer cells.
While scientists do not know why cancer cells continuously attract worms, they do have a theory: cancer cells release many of the same odour molecules as rotten apples, which we all know is appealing to other kinds of worms.
The next stage is to investigate if they can identify cancer when exposed to things other than cancer cells, such as urine or breath.
Although cats have very good noses, science ceases to give way to guesswork at this point.
Though not nearly as strong as a dog's, cats' noses are much larger than humans, and they are said to be able to distinguish between odours better than both dogs and people.
There is certainly some promise there, however, no scientific investigations have been conducted.
However, there are some amusing anecdotes.
In 2010, a woman from Franklin, Tennessee, went to see her doctor after a suspicious bruise appeared on her chest near where her cat had been pawing and pouncing the night before.
She realized that she had breast cancer.
A year before, a tale in Canada made headlines in which a guy from Calgary claimed that his cat had warned him of his lung cancer by constant pawing at his owner's left side.
The owner credits his cat, Tiger, who apparently was not previously very cuddly, with saving his life.
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