COVID-19 Scent Detection Dogs…

By Scott Weese on June 5, 2020

I’ve had countless questions about the potential for scent detection dogs to be useful for COVID surveillance.

 It’s an interesting idea and it’s dependent on COVID-19 infected people producing some different volatile compound than uninfected people (the virus itself not likely having a detectable odor.)

This pre-print paper can probably be filed under the ‘not likely to ever be published but an interesting story’ category. 

https://www.biorxiv.org/content/10.1101/2020.06.03.132134v1 

It’s a rambling description of a pilot study looking at scent detection for COVID surveillance. (Maybe another ‘let’s get something online first, who cares about the depth and editing’ paper. 61 authors is a bit extreme too, but I digress.) Pre-prints can be useful, but there has to be at least a modicum of effort.

Anyway, they collected armpit sweat samples from people with COVID and patients without signs of COVID.

18 dogs were involved; dogs that had been trained for explosive detection, search and rescue and colon cancer detection.

However, their table also lists an arson detection dog.

Further, they say that “We did not decide to work with drug detection dogs as there is always a possibility that COVID-19 positive or negative people use prohibited substances that would let catabolites be excreted by the axillary sweat.” But, their table lists a drug detection dog.

After training, they tested the dogs by seeing if they could detect samples from COVID-19 patients in scent boxes, compared to controls.

Three of the 18 dogs flunked out of COVID school as they were “unable to adapt to an olfactive search on a line of sample”.

Eight others were removed because they were “late in their testing period due to this necessary basic “retraining”. I’m not really sure what that means. I guess they weren’t completely kicked out of school but have to repeat the year, and no one wanted to wait to rush out the pre-print.

The authors say that left 8 dogs whose results they liked for the analysis; however, my math says that 18-3-8=7, not 8.

Numbers aside, results were interesting, as those dogs seemed to have high detection rates (84-100%).

It’s hard to say what this means and whether it’s relevant. I guess it means that if you look at some dogs, there’s potential. You have to find the right dog and the authors make a fair story when they point out they were looking at effective dogs, not whether it worked in the whole population. So, with proper training and selection, there might be some use.

Is this of any use?

It’s hard to say.

They tested samples from people with overt COVID, and that’s maybe not overly relevant. If someone has signs of COVID, we want to treat them like they have COVID until there are proper test results.

Where this might be more appealing is for asymptomatically infected people, where the dog might be an early warning device. The downside is that it requires a dog and a person to be in close proximity to the patient. Dogs are low (but not no) risk for picking up this virus, but there’s reasonable concern about handlers.

The practical nature of this is also questionable. The study mentions that armpit sweat is ‘easy and safe to collect’. If this relies on people taking samples of their armpit sweat, it’s no longer a quick, easy detection approach.

 It’s more appealing if the dog can be the entrance scanner to signal when a positive person walks into a workplace for example. If it requires individual sweat samples, the practicality drops a lot.

They have a few excuses for some of the false negative results, which seem to be a bit of a stretch or indicate potential issues applying this to the real world situation (e.g. distraction by a ‘too zealous television team’).

Some other discussion points are a bit hard to follow. They report false positives that they attributed to two male dogs and a young woman that ‘had been sampled during her fertile period .’

They better sort that out since that’s a reasonably common subset of the population.

The paper’s discussion devolves a bit from there “In Shakespeare’s day, a woman in her fertile period used to hold a peeled apple under her arm until the fruit became saturated with her armpit scent ; then she presented this “love apple” to her lover to inhale in order to provoke his sexual excitation.

Pheromones are defined as substances produced by an animal which conveys information to other individuals by olfactory means . And in such a situation androsterone and molecules like benzoate derivates, excreted in axillary sweat, enhance sexual attraction by men toward women near the end of follicular phase of the menstrual cycle when fertility is at highest .”

Overall, it’s an interesting pilot study that shows more study of this area might warranted.

In particular, it’s important to figure out whether dogs can be good detectors of COVID-19 infected people in situations where that’s useful….particularly in busy, high risk places in the community.

 It would be really cool to have a dog hanging out at the entrance of busy places, picking up infected people.