Dog Savior: Immediate Scent-Detection of SARS-COV-2 by Trained Dogs

Abstract

Molecular tests for viral diagnostics are essential to confront the COVID-19 pandemic, but their production and distribution cannot satisfy the current high demand. Early identification of infected people and their contacts is the key to being able to isolate them and prevent the dissemination of the pathogen; unfortunately, most countries are unable to do this due to the lack of diagnostic tools. Dogs can identify, with a high rate of precision, unique odors of volatile organic compounds generated during an infection; as a result, dogs can diagnose infectious agents by smelling specimens and, sometimes, the body of an infected individual. We trained six dogs of three different breeds to detect SARS-CoV-2 in respiratory secretions of infected patients and evaluated their performance experimentally, comparing it against the gold standard (rRT-PCR). Here we show that viral detection takes one second per specimen. After scent-interrogating 9,200 samples, our six dogs achieved independently and as a group very high sensitivity, specificity, predictive values, accuracy, and likelihood ratio, with very narrow confidence intervals. The highest metric was the negative predictive value, indicating that with a disease prevalence of 7.6%, 99.9% of the specimens indicated as negative by the dogs did not carry the virus. These findings demonstrate that dogs could be useful to track viral infection in humans, allowing COVID-19 free people to return to work safely. OV came up with the idea, obtained the funding, designed and supervised the training and the experimental process, and wrote the manuscript.AFV directed the training process and supervised the dog experiments in the field. AM, FO and EO trained the dogs and participated in all the experiments with them.

COVID Sniffer Dogs: Technical and Ethical Concerns

“…An important factor to be carefully analyzed is the collection and the preparation of the experimental samples for the dog's training. Studies testing the skill of dogs to recognize SARS-CoV-2-infected biological samples worked with a relatively small number of independent and single samples (19)(20)(21). This procedure cannot exclude that dogs could memorize the odor of the person, rather than that elicited by the SARS-CoV-2 infection.…”

“…The authors demonstrated that dogs were able to master the task with high rates of sensitivity (average 82.63%) and specificity (average 96.35%) after a week of training. A third study trained dogs to recognize SARS-CoV-2-infected people from respiratory samples (i.e., saliva, nasopharyngeal swabs or aspirates, and tracheal aspirates) obtained from subjects with mild, moderate, or severe symptomatology ( 21 ). Also, in this case, the results were very promising, with the testing procedure reaching 95.5% sensitivity and 99.6% specificity.…”

Scent dog identification of SARS-CoV-2 infections, similar across different body fluids

“…Our dogs were able to identify different COVID-19 disease phenotypes and phases of disease expression (sore throat, cough, cold, headache and aching limbs, fever, loss of smell and taste and/or severe pneumonia). Another scent dog detection study conducted by Vesga et al (2020) achieved promising results (95.5% average sensitivity and 99.6% specificity) and also planned real-life experiments 21 . These studies support the evidence of canines offering a reliable screening method for SARS-CoV-2 infections.…”

“…Clostridium difficile or mastitis causing pathogens 16,17 , hypoglycaemia in diabetics 18 , and virus infections in cell cultures 12,19 . In addition, several research groups worldwide currently train and deploy SARS-CoV-2 detection dogs 20,21 . In a pilot study, our group showed that dogs were able to detect inactivated saliva samples from COVID-19 patients with a sensitivity of 83% and specificity of 96% 22 , which has been confirmed by other groups training dogs to detect either respiratory secretions or sweat samples from COVID-19 patients 20,21 .…”

“…In addition, several research groups worldwide currently train and deploy SARS-CoV-2 detection dogs 20,21 . In a pilot study, our group showed that dogs were able to detect inactivated saliva samples from COVID-19 patients with a sensitivity of 83% and specificity of 96% 22 , which has been confirmed by other groups training dogs to detect either respiratory secretions or sweat samples from COVID-19 patients 20,21 . Despite these preliminary promising results, it remains to be shown whether dogs detect VOCs which are biofluid-specific or alternatively there is a more general change in odour of COVID-19 patients.…”