Monday, January 18, 2021
Home Science Medicine & Health Can Dogs Sniff Out Cancer? Can Rats Sniff Out Tuberculosis?

Can Dogs Sniff Out Cancer? Can Rats Sniff Out Tuberculosis?

Rat Sniffing

I know what you’re thinking – “dogs can sniff out cancer? What a bunch of nonsense!” And do you really want to trust rats with detecting a disease, when they were responsible for so much of the spread of disease throughout history? Well don’t hold it against them, because these animals didn’t know anything about it. In fact, these animals are now used for medical diagnoses, and people’s lives depend on them. It appears that dogs actually can sniff out cancer, and rats can sniff out tuberculosis (TB). Astonishingly, their amazing abilities to smell don’t even stop there.


The Scientific American podcast reported this a few years ago:

TB is the number-one infectious disease killer in the world. Early detection saves lives. But the most common way to diagnose TB, visually checking sputum samples for the microbe that causes the disease, requires sophisticated equipment and trained personnel. And it’s not all that accurate.

That’s where the rats come in. The critters are easy to train and can smell chemicals present with a TB infection. So scientists sent more than 20,000 sputum samples from 10,000 patients in Tanzania to be analyzed microscopically. They then presented the same samples to the rats. The results: the fancy microscopes found about 13 percent of the patients to be TB-positive. The rats identified an additional 620 cases, boosting the detection rate by 44 percent.

That may not sound like much, but remember a person with TB can infect another dozen or so people over the course of a year. So that’s more than 7,000 people that could be saved by a rat.

The New York Times gets into more specifics with why using rats is a good idea in medical purposes:

There are expensive and complicated laboratory tests for tuberculosis, and the World Health Organization recently endorsed a new machine that can give accurate results in under two hours. But the device costs $17,000, and each test requires a $17 cartridge.

Whatever else can be said about them, rats are cheaper.

Today, the most commonly used detection method in developing countries is smear microscopy. This 100-year-old technique involves collecting sputum, dyeing it with a substance that colors only Mycobacterium tuberculosis, the germ that causes TB, and examining the sample under a microscope.

The technique can be used in places where facilities are minimal, but it is not very sensitive — unless there is a high concentration of them, the bacilli are easy to miss, and that results in as many as 60 to 80 percent of positive cases going undiagnosed.

Studies suggest that the Gambian pouched rat can do better. [. . .] The animals’ sensitivity — that is, their ability to detect the presence of tuberculosis — ranged as high as 86.6 percent, and their specificity, or ability to detect the absence of the germ, was over 93 percent.

But if you thought that was amazing, it gets even better – and even more unebelievable. Rats are also being trained to detect land-mines. The BBC published an article saying this:

HeroRats are officially known as Mine Detection Rats (MDRs), specially trained by Apopo, a Belgian NGO that researches, develops and implements detection rat technology for humanitarian purposes like demining.

Landmines continue to be one of the world’s most dangerous weapons, especially in post-conflict countries. Scattered across 78 countries, these weapons of war can remain buried beneath the surface for decades, and their deadly nature does not diminish over time. According to The International Committee of the Red Cross, more than 800 people are killed and 1,200 maimed by landmines every single month  most of them children, women, and elderly.

The sleepy African coastal nation of Mozambique remains one of the most heavily mined countries in Africa. Tens of thousands of landmines were laid during the struggle for independence between 1964-1975 and the civil war that followed for nearly two decades. With no maps of mined territories, Augusto says working to clear the entire country is a “major challenge.”

Yet since Apopo’s rats launched into action in 2006, they’ve successfully cleared more than 6 million square meters of Mozambique’s countryside, uncovering 2,406 landmines, 992 bombs, and 13,025 small arms and ammunitions.

Time discusses the decision to use rats for land-mines:

Once in the ground, landmines are devilishly hard to get rid of, and efforts to remove the estimated 100 million buried around the world have prompted many an outlandish innovation. A Cambodian newspaper once proposed bringing over British cattle suffering from mad cow disease to roam the countryside setting off an estimated 11 million mines buried there. More conventional approaches to demining all have their flaws. Armored mine-clearance vehicles only operate on flat terrain; metal detectors are terribly inefficient because they pick up all the non-lethal bits of metal in the ground; dogs can smell the explosive in a land mine, but tend to get bored and run the risk of getting themselves blown up.

So when researchers from the Sokoine University of Agriculture in Morogoro, Tanzania, began training rats — known for their keen sense of smell — for the job, the Mozambicans were willing to give it a try. “Rats are intelligent, and they like to learn new things,” says Jared Mkumbo, a Tanzanian who supervises the training of the rats and their handlers. “You can train them to do exactly what you want them to do.” The project, run by an organization called Apopo, which is funded by the Flemish government in Belgium, is proving so effective that a new batch of mine-sniffing rats is scheduled to be deployed in Angola later this year.

As it turns out, there’s a TED talk that was released in 2010 – entitled “How I taught rats to sniff out land mines” – which you can see here:


As I also mentioned, dogs can indeed detect cancer. said the following:

Canines apparently possess a unique olfactory trait that allows them to sniff out the presence of cancer in the breath of people with the disease. And a new pilot study out of Austria suggests that dogs just might be the wave of the future as far as early detection is concerned, with recent trials showing an incredible sniffing success rate among patients with lung cancer.

The results of the preliminary trial, which were published recently in a scientific journal, indicate a fascinating ability among dogs to literally sense the presence of cancer earlier and more successfully than many modern detection methods. Using 120 breath samples, the European researchers were able to determine that the dogs used for the trial were successful in detecting 70 percent of cancers, which clearly illustrates the animals’ amazing ability.

“Dogs have no problem identifying tumor patients,” explained Peter Errhalt, head of the pulmonology department at Krems Hospital in Austria and author of the study, to AFP about the findings.

The investigation was a follow-up to earlier hypotheses about dogs’ apparent abilities to detect all sorts of diseases simply by being near people who had them. It also piggybacks earlier research from 2011 that identified a canine’s ability to detect early-stage bowel cancer, a condition that is apparently very difficult to detect using even modern medical technologies. (

“The specific cancer scent indeed exists, but the chemical compounds are not clear,” explained Dr. Hideto Sonoda from Kyushu University in Japan to BBC News last year about this mysterious and unknown cancer scent that dogs are able to pick up.

And it’s not just one type of cancer. This article from the Huffington Post gives an idea of the potential of canine intervention:

Give Donna Waugh three hours, and a reasonably capable dog, and she’ll train it to sniff out cancer.

Waugh, a trainer and president of the Arkansas Search Dog Association, is helping researchers in her area test their hypothesis that search-and-rescue dogs can be used to help detect ovarian cancer, one of the deadliest cancers for women.

But “training” is a misnomer, Waugh warns. Canines come by their detection skills naturally.

“Dogs already understand scent so far beyond what we can possibly imagine,” she told The Huffington Post. “They are experts. All we have to do is give them a scent we want them to pick out for us, then reward them immediately when they go to it.”

Cancer-smelling dogs have been grabbing headlines recently: U.K. resident Marian Cooper claimed her 6-year-old pug Flo alerted her to a lump in her right breast that turned out to be malignant. And Sharon Rawlinson, also of the U.K., told The Sun that her Cavalier King Charles spaniel kept gently pawing her left breast until she went to the doctor. [. . .]

“A big problem, and part of the reason why ovarian cancer is so deadly, is that in about 75 percent of women, we don’t pick it up until stage three or four,” said Dr. Alexander Burnett, director of the division of gynecologic oncology at the University of Arkansas Medical School, who is leading the experiment on ovarian cancer where Waugh volunteers. That critical screening void makes the possibility of using dogs to detect cancer especially exciting, Burnett said.

The results of the experiment’s initial portion are indeed exciting, but preliminary. A handful of dogs have been successfully trained to detect ovarian cancer, both in live tissues and by using urine samples. But, Burnett admitted, “We don’t know exactly what they’re smelling.”

[. . .] Other canine cancer studies have showed promise. A 2011 study out of Germany found that two dogs were able to detect lung cancer from breath samples with relatively high success, while a Japanese study found that a black lab was able to sniff out bowel cancer from a patient’s breath and stool samples.

As you can tell, we don’t know for sure how this canine detection is working, and there was a great deal of initial skepticism (not to mention that I didn’t believe it when I first heard it). But the science so far looks promising, and I am very hopeful. Perhaps we should be changing the colloquial term for dogs to “woman’s best friend.” From breast cancer to ovarian cancer, dogs are saving lives.

The Bottom Line published an article entitled “Dogs, Rodents May Prevent Future Epidemics” a few months ago, and I can see what they mean. They discuss that dogs may soon be trained to identify avian influenza in bird populations by smelling the feces of the birds. And perhaps using what we know from the animal world and from the science world, we may soon be able to create an artificial nose that could detect scents even better than dogs and mice.

Until then, we may (have to) become gradually more reliant on dogs and rats. As long as the science supports it, this could in fact be the best laid schemes of rats and man’s best friend.

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