US dogs suffer mystery respiratory illness: What we know so far

The mystery disease is causing dogs to experience symptoms that resemble other known respiratory illnesses, such as kennel cough and canine influenza.  (Image credit: Westend61 via Getty Images)

Dogs across the U.S. are getting sick with an unexplained respiratory illness. 

As of Monday (Nov. 27), at least 14 states, including Oregon, New Hampshire, Colorado and Massachusetts, have reported cases of pet dogs of different breeds developing symptoms including cough, runny nose, lethargy and a loss of appetite. In Oregon, for example, more than 200 cases have been reported since mid-August. However, the first cases of the outbreak are believed to have been reported in New Hampshire as early as last year, an expert told Live Science. 

The mystery illness' symptoms resemble those of common respiratory diseases that affect dogs, such as kennel cough and canine influenza. However, the infection appears to last longer than those diseases typically do and seems resistant to treatment with antibiotics, vets say. 

Here's what we know so far about the outbreak. 

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What are the symptoms of the new dog illness?

The unexplained dog disease is similar to common respiratory illnesses that affect canines. It typically starts with a cough that moves on to a fever, sneezing, a runny nose and watery eyes. However, not all the affected dogs have shown the same combination of symptoms. 

Normally, dogs recover from respiratory illnesses fairly easily, either on their own or with the help of antibiotics in the case of bacterial infections, Dr. Kurt Williams, director of the Oregon Veterinary Diagnostic Laboratory at Oregon State University, told The New York Times. Usually dogs recover from kennel cough, for example, within seven to 10 days. However, this outbreak is different. 

"In these dogs, either it lingered for longer or it took a downward spiral and led to very serious outcomes, including death," Williams said. It seems that serious outcomes are more likely to happen in older dogs or those with existing health issues, The New York Times reported.

What is causing the dog respiratory infection?

The cause of the outbreak among U.S. dogs is still unknown. However, some scientists think the culprit is a type of "funky bacterium" that has never been seen before, based on samples gathered from dogs in three states. 

"It’s smaller than a normal bacterium in its size and in the size of its genome," Dr. David Needle, a senior veterinary pathologist at the University of New Hampshire, told NBC News. "Long story short, it's a weird bacterium that can be tough to find and sequence," he said. (Sequence refers to analyzing an organism's DNA code.) 

Needle and his team have been tracking the outbreak since last year. So far, they have genetically sequenced 30 clinical samples from dogs that fell ill in New Hampshire last year, as well as 40 dogs from Rhode Island and Massachusetts that got sick this year. Twenty-one of the 30 New Hampshire samples were identified as the same unusual bacterial species, NBC reported. And 7% of the Rhode Island and Massachusetts samples also contained the microbe, Needle told Live Science in an email. 

Related: Why do dogs have cold noses?

The researchers have yet to publish their findings in a peer-reviewed journal, but they're sharing what they've found so that vets are kept as informed as possible. Needle's team hasn't been able to grow the bacteria in lab dishes yet, so they haven't had the opportunity to directly test how antibiotics affect it, Needle told NBC News. However, they can pull some clues from its structure and genetic code.

The specific pathogen behind the ongoing outbreak hasn't been identified, Needle stressed, and it's still unclear whether the one they've found is the same one infecting dogs across the country. Needle thinks the newfound bacterium may have evolved from a microbe normally found in the dog microbiome — the collection of microbes and viruses that live inside and on the surface of their body. 

Whatever its cause, the disease currently appears to be specific to dogs. There have been no reported cases in humans, Mike Stepien, a spokesperson for the the United States Department of Agriculture Animal and Plant Health Inspection Service, told NBC News.

Cases of the disease have so far been reported in at least 14 states.  (Image credit: NickyLloyd via Getty Images)

Where has the new dog disease been reported?

Potential cases of the new dog respiratory illness have been reported in at least 14 states, American Veterinary Medical Association (AVMA) president Dr. Rena Carlson told USA Today on Nov. 27. The affected states include California, Colorado, Florida, Georgia, Idaho, Illinois, Indiana, Maryland, Massachusetts, New Hampshire, Oregon, Rhode Island, Vermont and Washington.

As far as we know, New Hampshire was the first state to report cases, Needle told Live Science. 

There is no official count of the total number of infections nationwide, so a lot of our understanding of the outbreak is down to anecdotal reports from vets. 

It's also difficult to get a full picture of how many infections there have been because scientists still don't know what is causing the disease, so vets can't accurately diagnose or test for it, Williams told The Associated Press.

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What advice do vets have for dog owners about the new illness?

As the holiday season approaches, people are more likely to put their dogs in kennels or send them to doggy daycare, Dr. Lindsey Ganzer, a veterinarian and chief executive at North Springs Veterinary Referral Center in Colorado, told The New York Times. This could trigger an increase in infections as dogs are likely to come in closer contact with one another. 

"We're really hoping just with getting the word out there that people are less inclined to do that," Ganzer said. Since late October, she's treated about 35 dogs with the disease and all of them had recently spent time in boarding facilities, doggy day care or dog parks. Four dogs died or had to be euthanized. "The veterinary community as a whole is kind of scared," she said. 

However, other vets think that dog owners should be cautious but not worried about the infection. In Oregon, for example, the number of dogs with the mysterious infection represents only a small fraction of the total number of dogs in the state, Dr. Stephen Kochis, chief medical officer for the Oregon Humane Society, told The New York Times. 

Although the current outbreak is being caused by an unknown pathogen, similar respiratory diseases, such as kennel cough, also cause periodic outbreaks of infection, the ODA said

To help keep dogs healthy, Williams said that owners should make sure dogs' vaccinations are up to date, but don't panic, he told the AP. Vaccinations may include those for canine influenza, Bordetella (a common cause of kennel cough) and parainfluenza

If a dog is sick, people should keep it at home and avoid using communal water bowls or toys, as well as report any symptoms to their vet, the ODA said. 

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Emily Cooke
Staff Writer

Emily is a health news writer based in London, United Kingdom. She holds a bachelor's degree in biology from Durham University and a master's degree in clinical and therapeutic neuroscience from Oxford University. She has worked in science communication, medical writing and as a local news reporter while undertaking journalism training. In 2018, she was named one of MHP Communications' 30 journalists to watch under 30. (