Buzz
Certain animals, such as dogs, are renowned for their exceptional senses that allow them to detect a wide range of environmental factors beyond human perception. Their remarkable ability to be trained has led to their use in various fields, from detecting drugs and explosives to more recently identifying diseases, particularly cancer. Dogs aren't the only animals showing potential in this field. Here are ten animals that could potentially detect cancer in humans.
10. Rats
A 2021 study conducted in Korea demonstrated that trained rats could identify toluene, a chemical marker associated with lung cancer. To communicate their findings, the rats were taught to jump onto a floating platform when they detected the scent of toluene, which is an unusual method of communication.
In a bid to enhance the realism of the experiment, the rats were exposed not just to samples of toluene mixed with other scents, but also to real human breath samples collected in sealed plastic bags. Some of these breath samples were artificially spiked with toluene. After over a thousand trials, the rats were able to detect the chemical with an accuracy of about 82%.
9. Bees
Not only mammals but also insects are contributing to disease detection in humans. Bees have an incredibly sharp sense of smell, capable of detecting even trace amounts of substances in the air. They have already been used to detect diseases such as tuberculosis and diabetes.
Moreover, bees can be trained much faster than animals like dogs. Their antennae help them accurately differentiate specific odors in a mix, such as when detecting human breath samples. Susana Soares, a Portuguese designer, created a sleek glass device called “Bee’s” while working on her Master’s degree. This device allows people to safely exhale into a chamber with bees that have been trained to identify certain chemicals in exchange for a sugar reward.
8. Pigeons
In a rather unusual experiment, researchers in the U.S. tested whether pigeons could detect breast cancer by analyzing images. Remarkably, they performed as well as humans! Despite having brains no larger than a fingertip, pigeons possess exceptional mental abilities, particularly when it comes to images. They can recall up to 1,800 images and distinguish between people, facial expressions, and even letters of the alphabet.
In the cancer research experiment, pigeons were trained to differentiate between microscope images of cancerous and non-cancerous tissues, receiving rewards for correct responses. When shown unfamiliar images, the pigeons applied their training, successfully identifying the images even when altered by zooming or discoloration. These pigeons are believed to hold promise in helping to validate future methods of cancer detection through image analysis.
7. Ants
Ants, much like bees, are equipped with highly sensitive antennae that enable them to detect substances beyond the range of human perception. As we've discovered, cancerous tumors release distinctive chemicals that have a specific odor. These compounds are not confined to breath; they also appear in urine. In 2023, scientists found that ants were exceptionally accurate in detecting these chemicals in the urine of mice.
It is believed that ants could offer a more affordable and less invasive alternative for early cancer detection. But how do you train ants to react to these chemicals? Similar to the other animals in this study, ants were trained with rewards, specifically sugar water. When the sugar water was withheld, the ants stayed longer near the urine samples containing the cancer-related chemicals, anticipating their reward.
6. Dogs
Naturally, man's loyal companion had to make an appearance here. With a sense of smell estimated to be 10,000 to 100,000 times more powerful than our own, it's no surprise that dogs can detect cancer too. They are capable of identifying cancer in expelled substances like breath and urine, similar to the ants and bees previously mentioned. Additionally, dogs can even detect cancer while it's still in situ, meaning it has not yet spread from the original site.
This is excellent news, as early detection is essential, considering that cancer becomes much more difficult to treat once it has spread. Dogs have been trained to detect cancer in breath, plasma, urine, and saliva. Typically, it takes around 300 samples to teach them the scent and enable them to apply it to new, unseen samples. While some organizations use dogs for direct cancer detection, other researchers are working to develop a mechanical nose that can replicate the dog's ability, allowing the animals to carry on with their daily lives.
5. Fruit Flies
You might be surprised to find that fruit flies actually have fewer than half the number of odor-sensing receptors compared to bees. So, why are they used? Perhaps because they communicate more effectively than bees, as researchers in Germany and Italy discovered. The scientists managed to genetically modify the flies so that they glow when they sense certain chemicals.
In this study, air containing the scent of breast cancer cells and healthy breath tissue was directed toward the flies. Scientists then observed, under a microscope, the flickering fluorescent patterns on the flies' antennae as they detected the scents. Fruit flies have a naturally adaptable genome, making them easy to modify genetically. In addition, they are inexpensive to breed and possess extremely sensitive olfactory receptors, offering a promising approach to early cancer detection.
4. Worms
In this research, the focus is on roundworms, tiny creatures measuring only about 1mm, far smaller than the garden-dwelling earthworms. While these worms may not be interested in mud, they show a keen attraction to cancer cells, especially when they’re hungry. In the experiment, scientists from Korea placed 50 worms on microscope slides alongside healthy and cancerous human cells. Approximately 70% of the worms moved toward the cancer cells.
Although the exact reason why cancer cells attract these worms is unknown, scientists have a theory: Cancer cells release many of the same odor molecules as rotting apples, which are known to attract other species of worms. The next phase of the research will explore whether these worms can detect cancer through substances like urine or breath, rather than being directly exposed to cancer cells.
3. Humans
As demonstrated by the various studies mentioned above, cancer has distinct odors, raising the question of whether humans can detect them. While our sense of smell is not as powerful as that of many animals, particularly dogs, one Scottish nurse with an extraordinary sense of smell believes it might be possible for some people to detect cancer by scent.
Joy Milne, a former nurse, detected a change in her husband's skin odor a full 12 years before his Parkinson's disease diagnosis. Her exceptional sense of smell was later tested in clinical trials, where it was found that she could identify specific molecules in the sebum associated with Parkinson's disease. Additionally, she mentioned that cancer patients had a distinct smell when she worked as a nurse.
In 2018, Joy visited a training facility for cancer-sniffing dogs to assess her own abilities by sniffing masks that cancer patients and healthy individuals had breathed into. The results were quite encouraging, with her accurately identifying the owners of most of the masks. However, some experts suggest that the smells detected by humans may not be directly linked to cancer, but rather to the symptoms or side effects of treatments, leaving the matter unresolved.
2. Cats
Here, science gives way to speculation, although cats possess surprisingly sharp noses. While not as powerful as a dog’s, a cat’s sense of smell is far superior to that of humans, and there is a belief that they can distinguish odors better than both dogs and people. Although scientific research on this is scarce, there are fascinating anecdotes.
In 2010, a woman from Franklin, Tennessee, sought medical attention after discovering a mysterious bruise on her chest where her cat had been persistently pawing the night before. It turned out to be breast cancer. A year earlier, a similar story made headlines in Canada, where a man from Calgary attributed his cat’s constant pawing at his left side to the detection of his lung cancer. The man credits his cat, Tiger, who was not typically affectionate, with saving his life.
1. Locusts are often a key focus in scientific studies, much like fruit flies. Researchers already understand much about their biology and neural wiring, and their keen sense of smell has also been studied. These insects have been used in experiments for detecting explosives, and more recently, scientists explored how they might contribute to disease detection. Rather than training the locusts to react to cancerous cells directly, electrodes were affixed to their brains to observe how they responded to gases emitted by both cancerous and healthy cells.
The findings were remarkable: locusts were not just capable of distinguishing between healthy and cancerous cells, but could also tell apart three different types of cancer. While this breakthrough is impressive, scientists are not planning to involve live locusts in medical testing. Instead, their goal is to replicate the biological mechanisms behind this sensitivity to develop artificial detection methods.
Though it may sound a bit unsettling, the research into locusts’ ability to detect cancer offers an intriguing glimpse into how we could use biology for medical purposes. The locusts' responses to cancer gases are a step toward potentially revolutionary methods of diagnosis, but the future of this research lies in reproducing their ability through technology, not through live insect testing.
