Study investigators Adolfo García-Sastre, PhD, left, and Guojun Wang, PhD, Postdoctoral Fellow
Dogs are becoming increasingly friendly hosts for a surprising array of influenza viruses, a situation that could pose a potential threat to humans. That is the finding of a new study from the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine at Mount Sinai, published June 5, 2018, in mBio.
The results were based on scientific evidence that dogs in southern China had the capacity to serve as “mixing vessels” for influenza viruses they receive from swine and birds—two animals considered to be the most common reservoirs of influenza viral genetic diversity.
“The more diversity we see in influenza viruses, the greater the chance they could jump from one host to another,” says the study’s lead author, Adolfo García-Sastre, PhD, Professor of Microbiology at the Icahn School of Medicine, and Director of the Global Health and Emerging Pathogens Institute. He is also Director of the Center for Research on Influenza Pathogenesis, one of five National Institutes of Health (NIH) Centers of Excellence for Influenza Research and Surveillance. The research took place in the Guangxi region of southern China, an area where diverse animal species are raised in proximity to one another and intermingle in live-animal markets.
In the study, researchers swabbed the noses of some 800 dogs that had all been brought to veterinarians or clinics in the region after showing respiratory symptoms consistent with canine influenza. The scientists sequenced the complete genomes of 16 influenza A viruses obtained from the dogs. All of these strains represented introductions of H1N1 swine influenza viruses circulating in pigs in Asia and Europe into these dogs.
They also found a set of three new viruses (H1N1r, H1N2r, and H3N2r) in which these swine-origin canine influenza viruses exchanged genes with previously identified avian-origin H3N2 canine influenza viruses.
Flu viruses have eight mini chromosomes and when two different strains infect the same cell they can exchange genetic segments, a process known as reassortment. All pandemic flu viruses that have been tracked have involved reassortment. The 2009 H1N1 swine-origin human influenza pandemic, for example, was a derivative of two different strains of swine influenza, one that had been circulating in Asia and Europe and the other in the Americas, particularly North America. That pandemic virus traced to a very small region in central Mexico, and was responsible for more than 17,000 deaths worldwide when it jumped from pigs into humans.
There is no known case of a human contracting a canine flu. Nor is it certain that the new strains of dog flu virus discovered in China would have that transmission capability. Still, as Dr. García-Sastre points out, the potential exists, especially in light of the frequent contact between pets and their owners. Moreover, the health risk increases for humans who have not previously been exposed to these viral strains and have not built an immunity to them.
Dr. García-Sastre does not predict a new pandemic, but he says there is a need for additional research and heightened vigilance by public health authorities around the world.
“We must start thinking about dogs as potential reservoirs for influenza viruses,” he says. “The more awareness we create, the more likely that countermeasures can be developed by countries to diminish the circulation of influenza virus in domestic animals.”