While humans have developed increasingly sophisticated technology to detect cancer, animals have surprisingly emerged as key allies in this fight. Their extraordinary olfactory senses and natural instincts have made certain species exceptionally skilled at identifying cancer in humans, a phenomenon now being explored by researchers worldwide.

Dogs are perhaps the most well-known cancer-detecting animals, and for good reason. A dog’s sense of smell is estimated to be between 10,000 to 100,000 times more sensitive than that of humans. Their nasal cavity houses around 300 million olfactory receptors, compared to just 5 million in humans. This powerful olfactory system enables them to detect volatile organic compounds (VOCs), which are chemicals produced by cancer cells and released into the body.

While machines like gas chromatography-mass spectrometry can detect VOCs, animals often outperform these devices in terms of speed and sensitivity. [Ed: Another good reason to get that dog.]

Research has demonstrated that dogs can identify several types of cancer, including lung, breast, ovarian, prostate and colorectal cancers. In studies, trained dogs have shown impressive accuracy rates, sometimes detecting cancer with a success rate above 90%. For example, in a groundbreaking study published in British Medical Journal in 2004, dogs were able to detect bladder cancer by sniffing urine samples. More recently, dogs have been trained to differentiate between breath samples of healthy people and those with lung cancer. The results suggest a promising future for integrating canine detection in clinical settings, especially as a non-invasive diagnostic tool.

While dogs receive most of the spotlight, rats have also proven to be surprisingly adept at cancer detection. One organisation, APOPO, has successfully trained African giant pouched rats, initially used to detect landmines, to sniff out tuberculosis in human sputum samples. Recognising the potential for detecting other diseases, scientists have begun exploring whether these rodents could also be used to detect cancer. Though research in this area is still developing, preliminary findings are promising.

Beyond dogs and rats, studies are examining other species for their cancer-detecting potential. For instance, ants have recently emerged as an unexpected candidate. French researchers found that ants could be trained to detect cancer cells. In an experiment, ants quickly learned to distinguish between healthy and cancerous cells using olfactory cues. Given that ants have a relatively simple nervous system and can be trained much faster than dogs, this area holds exciting potential for rapid, cost-effective cancer diagnostics.

Honeybees can do it too. These insects use their sense of smell to detect a wide range of chemical compounds. In one study, scientists exposed honeybees to the scent of cancer cells and found that the bees would stick out their tongues (a reflex known as the proboscis extension) when presented with cancerous samples. [Ed: We can empathise with this reaction.] Although still in the experimental phase, this research indicates that honeybees could one day serve as a diagnostic tool. To that end, UK-based product designer Susana Soares has designed a glass apparatus, called "Bee's" that features a large chamber and a smaller connected chamber housed within it to assist with that testing.

Sometimes it’s not about smelling, but rather about seeing.

Inspired by the mantis shrimp's superlative “hexnocular” eyesight and ability to detect polarisation, a the group of researchers are collaborating to build cameras that could be used to help identify cancerous cells, long before the detection of other symptoms or signs.

Finally, it turns out that pigeons, although tiny-brained, are really good at distinguishing between different types of microscopic images used in the hunt for breast cancer.

Thank you animals.

Story Idea: Andrea Jansz
_______________________

References

ChatGPT
nationalgeographic.com/animals/article/these-animals-detect-disease-cancer-covid
newatlas.com/science/cancer-sniffing-ants-accurate-as-dogs
smithsonianmag.com/innovation/can-bees-be-trained-to-sniff-out-cancer
susanasoares.com/index.php?id=56
listverse.com/2023/02/25/10-amazing-animals-that-can-detect-human-diseases

Images

1. A beagle sniffing blood samples. Credit: BioScentDx
2. Red wood ant. Photo credit: Maciej Olszewski
3. Bees in hive. Image credit: rawpixel.com
4. "Bees's" glass apparatus. Credit: Susana Soares
5. Video: "The Snail-Smashing, Fish-Spearing, Eye-Popping Mantis Shrimp" | Deep Look by KQED and PBS Digital Studios, 2017