“What this paper tells us is that out there in the world, viruses are spilling over in human populations all the time . . . it means we need to make sure our health systems are getting ready to find any new events like this.” - Peter Daszak, British zoologist, President, EcoHealth Alliance
“If you think dogs can’t count, try putting three dog biscuits in your pocket and then give him only two of them.” - Phil Pastoret, American author
Microbes that are transmitted from animals to humans (zoonoses) have caused 60% of the more than 140 emerging infections in the past 50 years. Animals are therefore a common feature in these Germ Gem posts. Bats have received the most attention because they are the source of several coronaviruses, including SARS-CoV-2 (the cause of the COVID-19 pandemic). I did, however, highlight dogs in a September 15, 2019 Germ Gem post on rabies—an almost uniformly fatal viral infection linked to dog bites, primarily in the developing world. In this post, I again feature dogs and have both bad news and good news about “man’s best friend.”
Coronavirus recap. Until recently, only seven coronaviruses were known to infect humans. Four of these coronaviruses (types 229E, NL63, OC43, and HKU1) cause mild to moderate upper-respiratory tract illnesses, like the common cold. Most people have been infected with one or more of these viruses at some point in their lives. Three of the seven coronaviruses (SARS-CoV-1, MERS-CoV, and SARS-CoV-2) emerged in the 21st century. They cause zoonotic infections that can be severe and are sometimes fatal. An eighth coronavirus, a dog coronavirus dubbed CCoV-HuPn2018, has now been implicated in an outbreak of pneumonia in humans.
The bad news: the CCoV-HuPn-2018 story. Dogs, as well as other animals, can be infected with coronaviruses (CoVs) that only affect them. For example, CCoV, canine coronavirus disease, causes a highly infectious gastrointestinal infection in dogs, especially puppies. Now it appears that another canine coronavirus may be responsible for causing respiratory tract infections in humans.
In the May 2021 issue of Clinical Infectious Diseases, Anastasia Vlasova, a DVM, PhD scientist at Ohio State University, and her colleagues reported finding evidence of the novel coronavirus, CCoV-HuPn-2018, in a nasopharyngeal swab from a child who had been hospitalized with pneumonia in Sarawak, Malaysia. They detected this new coronavirus in the course of evaluating a newly developed test that could detect a wide variety of coronaviruses. Upon finding CCoV-HuPn-2018 in the specimen from the child, they went on to test 301 archived samples collected in 2017-18 from patients with pneumonia in two Sarawak hospitals. Eight were confirmed to contain CCoV-HuPn-2018. Seven of the eight were from children less than 5 years old. After 4-6 days of hospitalization, all of the patients recovered.
CCoV-HuPn-2018 was subsequently determined to be a recombinant virus, that is a naturally occurring recombination of more than one virus genome, in this case a recombination of a novel canine-feline (dog-cat) alphacoronavirus. (SARS-CoV-2 is a betacoronavirus.) If CCoV-HuPn-2018 is confirmed as a pathogen, it would be the eighth known coronavirus to cause infection in humans. The authors of this research paper concluded, “Our findings underscore the public health threat of animal CoVs and a need to conduct better surveillance for them.”
The Good News: Let’s hear it for the “sniffers.” A dog’s sense of smell is said to be 1,000 to 10,000 times better than that of humans. The dog’s super-powered sense of smell is due to its ability to detect volatile organic compounds, the chemicals excreted through waste products such as urine, saliva, and sweat. Their nostrils connect to dozens of crisscrossing cavernous tunnels that allow scents to linger.
Because of their keen sense of smell, dogs are used in search and rescue missions in the wake of natural disasters, in military operations (smelling out hidden explosives), searching for contraband at airports, tracking down poachers, and sniffing out endangered and invasive species. There is also some evidence of the dog’s potential use in medicine by detecting early signs of Parkinson’s disease, diabetes, several kinds of cancer, and malaria. Now it appears that dogs can actually smell a virus—and not just any virus but SARS-CoV-2, Public Enemy No. 1.
French researchers at France’s national veterinary school and clinical research unit of Paris’s Necker-Cochin hospital collected samples—cotton pads pressed for two minutes under participants’ armpits—from 335 people aged between six and 76. In April, they reported that COVID-19 sniffer dogs (those trained with positive reinforcements) were able to detect SARS-CoV-2 in human specimens with 97% accuracy. This is comparable to the results of the polymerase chain reaction assay, the standard test requiring a nasopharyngeal specimen. Moreover, these sniffer dogs were also 91% correct in identifying negative samples.
A proof-of-concept study by University of Pennsylvania’s School of Medicine researchers published in April 2021 in the journal PLOS ONE, showed that SARS-CoV-2 has an odor that trained dogs can identify in urine and saliva with an accuracy of 96%. Similar studies have concluded or are underway in other parts of the world, including the UK.
Dogs are already deployed at Finland’s Helsinki-Vantaa International Airport to sniff out COVID-19 infected passengers. If the COVID-19 dog “sniffer” studies are borne out, we may soon see dogs deployed for COVID-19 screening at additional airports as well as at other venues. It may well be that “sniffer” dogs will be helpful in curbing the spread of COVID-19—proving once again, that a dog is indeed “man’s best friend.”