When it comes to accurately diagnosing a disease, you might think you need expensive, high-tech machinery and equipment capable of looking deep into what’s going on in the body beneath the skin.
But while these high-tech instruments are certainly amazing, they’re not the only ones capable of detecting conditions. In fact, you might even share a home with one of these powerful disease-detecting agents.
There are numerous cases where unsuspecting pet owners find out that they had a health problem thanks to their pets.
Examples include dogs licking, sniffing and even trying to chew at spots on their owners’ skin that were later diagnosed as malignant melanomas.
In fact, many species of animals (from the microscopic worm C elegans even ants, mice and dogs) have successfully demonstrated the ability to detect diseases in people and from biological samples in experiments.
The diseases discovered are diverse: from cancer and urinary tract infections to covid-19 or gastrointestinal infection. Clostridium difficile.
Many of these diseases are potentially serious, especially in vulnerable and immunocompromised patients, so early and accurate detection is essential.
These are just some of the amazing animals that can reveal ailments in humans.
Dogs
They are possibly the best-known example of an animal that can detect a variety of diseases, including Parkinson’s, bladder cancer and malaria.
Epileptic seizures and low blood sugar levels in diabetic patients can also be revealed by specially trained medical alert dogs.
A dog’s impressive olfactory sense is apparently key to their ability to detect specific odors, even at incredibly low concentrations. In fact, a dog’s sense of smell is thought to be more than 10,000 times better than our own. They can even use their nostrils independently to investigate new scents.
Biodetection and medical alert dogs are initially trained to associate specific odors with a positive reward, such as a treat or toy. They are then trained to recognize odor 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 handlers, sometimes pawing at them or nudging them to signal that they need to take action for their safety.
Rats
Rats are also excellent at detecting specific odors.
The giant African species has been trained to detect the smell of explosives from landmines in Mozambique.
They are also proving to be valuable partners in medical detection, playing an important role in finding tuberculosis in sputum samples recovered from suspected cases.
The rats are fast, taking just 20 minutes to sift through 100 patient samples. They use their sense of smell to detect the distinctive chemical signature of tuberculosis in samples. Their payment for a job well done is a snack of avocado and banana.
This makes these trained rats a valuable option when time and money may be limited at diagnostic and detection facilities. They have an incredible success rate, accurately detecting positive TB cases 81% of the time.
Bees
These insects can detect signs of certain diseases in samples, including lung cancer, tuberculosis and COVID-19.
They are extremely sensitive to low concentration odors, making them able to detect chemical changes in a similar way to dogs and rats.
Researchers have been able to train bees to respond to the presence of specific odors by having them extend their tongues to obtain a sugar reward. With training, this response becomes consistent and highly sensitive to odors related to pathological states.
This ability makes bees useful for detecting diseases in the same way as other animals. Their size could make them an even more efficient and low-cost option for rapid “analysis” of samples.
Higher senses
But how can animals identify the presence of specific diseases?
It has to do with the ability that many of them have to detect small changes in a person’s olfactory chemical profile.
Many species, including dogs, rats and bees, can identify very subtle changes in so-called volatile organic compounds (VOCs) that the body releases at very low levels, even when one is healthy.
In fact, exhaled human breath contains approximately 3,500 different VOCs. The composition and concentration of VOCs that the body releases changes depending on a person’s health and will be different if they are fighting an infection or dealing with a health problem.
The ability of animals to detect diseases does not only benefit humans. For example, the worm C elegans Not only can it detect cancer in human samples, but its superior olfactory senses help it detect it in samples from dogs and cats.
The abilities that different species have to accurately reveal diseases could make trained detection animals an effective, noninvasive, fast and cost-effective way to identify particular conditions. It may even further enhance positive interactions between people and animals.
In particular, due to regulations, animals used to identify diseases are currently only considered detection “tools” used in conjunction with medical diagnostic techniques. But if regulatory frameworks allow, detection animals could one day become a key diagnostic component.
In fact, sniffer dogs were faster (and cheaper) at detecting Covid-19 than routine PCR testing. By understanding the detection capabilities of animals, we could help further improve laboratory analyses by applying some of their amazing skills.
While exploiting animals’ olfactory prowess can be useful to us, it is important to remember that the health and welfare of the species involved must also be prioritised. The ethics of working animals must always be taken into account alongside considerations of cost, safety and efficiency of any disease detection programme.
*Jacqueline Boyd is a Senior Lecturer in Animal Science at Nottingham Trent University.
*This article was first published on The Conversation and is reproduced here under a Creative Commons license. Click here to read the original version and see links to the studies cited.
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