When it comes to accurately diagnosing disease, you might think that you need expensive, high-tech machines and equipment that can peer deep beneath the skin to see what’s going on inside the body. But while these high-tech instruments are certainly incredible, they’re not the only tools capable of detecting disease. In fact, you might even be sharing a home with one of these powerful disease-detecting tools.
There are countless examples of unsuspecting pet owners discovering that they have a health problem with their pet. Examples include dogs licking, sniffing and even trying to chew spots on their owner’s skin – spots that were later diagnosed as malignant melanoma.
In fact, there are many species of animals – from the microscopic worm C elegansto ants, mice and dogs – have all successfully demonstrated their ability to detect diseases in humans and biological samples during experiments.
The diseases identified are diverse – from cancer and urinary tract infections to COVID-19 and gastrointestinal infection, Clostridium difficile.
Many of these diseases can be serious, especially in vulnerable and immunocompromised patients. Therefore, accurate and early detection is essential.
Here are just a few of the amazing animals that can detect disease in humans:
Dogs
Dogs are perhaps the best-known example of an animal that can detect a range of diseases, including Parkinson’s disease, bladder cancer and malaria. Epileptic seizures and low blood sugar in diabetics can also be detected by specially trained medical alert dogs.
It seems that a dog’s impressive sense of smell is the key to their ability to detect specific scents, even at incredibly low concentrations. In fact, a dog’s sense of smell is said to be over 10,000 times better than ours. They can even use their nostrils independently when investigating new scents.
Biodetection and medical alert dogs are initially trained to associate specific scents with a positive reward, such as a tasty treat or toy. They are then trained to recognize scent changes or physical and behavioral changes in their handler that predict a seizure (or other health event).
Biodetection dogs typically freeze when they recognize a scent, waiting for their reward. Medical alert dogs often interact with their handler – perhaps pawing or nudging them to signal that they need to take action for their own safety.
Rats
Rats are also very good at smelling specific odors.
The African giant pouched rat has been trained to detect the scent of explosives from landmines in Mozambique. These rats have also proven to be valuable medical detection partners, playing an important role in detecting tuberculosis in sputum samples recovered from suspected cases.
The rats are fast, taking just 20 minutes to evaluate 100 patient samples. They use their sniffing skills to detect the telltale chemical signature of tuberculosis in samples.
Their payment for a job well done is a treat of avocado and banana. This makes these trained rats a valuable option where time and money may be limited in diagnostic and screening facilities. These rats have an incredible success rate – they accurately detect positive tuberculosis cases in 81% of cases.
Bees
Even honeybees can detect signs of certain diseases in samples, including lung cancer, tuberculosis and COVID-19.
Honeybees are extremely sensitive to low odor concentrations, allowing them to detect chemical changes in a similar way to dogs and rats.
Researchers have been able to train honeybees to respond to the presence of specific odors by rolling out their tongues for a sugar reward. With training, this response becomes consistent and highly sensitive to odors associated with disease conditions.
This ability makes honeybees useful for detecting diseases in the same way as other animals. Their size could make them an even more efficient and cheaper option for rapid sample screening.
Superior senses
But how can animals identify the presence of specific diseases? It has to do with the ability of many animals to detect small changes in a person’s chemical scent profile.
Many species (including dogs, rats, and bees) can detect very subtle changes in substances called volatile organic compounds (VOCs), which the body releases in very low concentrations, even when they are healthy. In fact, exhaled human breath contains approximately 3,500 different VOCs. The composition and concentration of VOCs that the body releases changes based on a person’s health – and will be different if they are fighting an infection or dealing with a health problem.
The disease detection capabilities of animals are not only of benefit to humans. The worm C elegans can not only detect cancer in human samples, but thanks to their superior sense of smell, they can also detect cancer in samples from dogs and cats.
The ability of different species to accurately detect diseases could make trained detection animals an effective, non-invasive, fast and cost-effective way to screen for specific health conditions. It could even further enhance positive interactions between people and animals.
Due in large part to regulations, animals used for disease detection are currently only seen as screening “tools” to be used alongside medical diagnostic techniques. However, if regulations allow, detection animals could one day become an important diagnostic tool.
Indeed, detection dogs were faster (and cheaper) at screening samples for COVID-19 than routine PCR testing. By understanding the detection capabilities of animals, we may be able to help further improve laboratory diagnostic tests by harnessing some of their amazing skills.
While exploiting the sniffing skills of animals can be useful to us, it is important to remember that the health and welfare of the animals involved must also be prioritized. The ethics of working animals must always be taken into account, alongside considerations of the cost, safety, and efficacy of any widespread disease screening programs that involve them.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Jacqueline Boyd is affiliated with The Kennel Club (UK) by membership, as Chair of the Activities Health and Welfare Subgroup and a member of the Dog Health Group. Jacqueline is a full member of the Association of Pet Dog Trainers (APDT #01583) and also writes, consults and coaches independently on dog matters, in addition to her academic affiliation with Nottingham Trent University