Here are 5 questions about the mystery dog illness making news

Researchers are trying to discover what’s behind the rise in “atypical kennel cough"

woman with her dog

Freelance writer Michelle Hiskey bonds with her dog, Sheba, who may have fallen ill with a more severe form of kennel cough afflicting canines across the United States.

Michelle Hiskey

In recent weeks, claims about a mysterious respiratory illness sickening dogs across the country have spooked pet owners.

Dogs with what veterinarians have dubbed “atypical kennel cough” show more persistent and severe symptoms than those caused by run-of-the-mill kennel cough: a coldlike condition caused by a grab bag of viruses and bacteria. Many ill dogs have failed or been slow to respond to existing treatments. Some have even died.

Efforts to pin down a culprit have so far yielded more questions than answers. That’s fed fears of a new contagion. When Michelle Hiskey’s dog Sheba fell ill, for instance, her friends and family members blew up her phone with texts, concerned about what some on social media branded “COVID for dogs.” Hiskey, a freelance writer in Decatur, Ga., is “not generally a worrier,” but the horror stories she heard did startle her, she says.

Experts, including those who had previously sounded alarm bells, now say there’s most likely a simple explanation behind the cases. Here’s what we know and what still remains unknown.

What’s different about this mystery dog illness?

It’s not unusual for dogs to occasionally catch kennel cough, a chest infection that manifests most clearly in a honking cough, runny nose and sneezing. But beginning in late 2022 and surging the summer of 2023, more and more dogs seemed to be showing up to clinics, sicker than usual.

Cases of kennel cough are typically mild and resolve within a week or two. Dogs with atypical kennel cough can be feverish and fatigued on top of their other symptoms, and their symptoms can linger for several weeks. Taking antibiotics does not often lead to much improvement.

In some suspected cases, dogs have gone on to develop pneumonia, an inflammation of the lungs that in rare occasions can be deadly, says Mike Stepien, a spokesperson from the United States Department of Agricultural Animal and Plant Health Inspection Service, which is aiding state laboratories with diagnostic testing.

For Sheba, who first began hacking and wheezing at the start of November, two rounds of the antibiotic doxycycline and temaril-p, an anti-inflammatory drug, have significantly reduced but not eliminated her symptoms. She needs to be symptom-free for seven days to be declared healthy, but she still hasn’t gone a full week without coughing. “I just keep starting the clock again,” Hiskey says.

It can be normal for dogs to respond poorly to treatment, says Colin Parrish, a virologist at the Cornell University College of Veterinary Medicine. No antiviral drugs exist to combat kennel cough, and antibiotics sometimes have middling efficacy.

The standard prescription from veterinarians is rest and time.

How many cases are there?

No one knows for sure. No national program tracks diseases in dogs, making the count unclear, but so far, several hundred cases have been reported in over 16 states, from Rhode Island to California.

Oregon’s Department of Agriculture has launched a formal investigation into suspected cases of atypical kennel cough, counting more than 200 since August. In most states, however, reports remain anecdotal.

What’s causing dogs to get sick?

Scientists and public health officials do not yet know what is causing atypical kennel cough, but many doubt the cases all have one cause.

The small number of cases and the sporadic transmission patterns point away from a singular, highly contagious pathogen, says Jane Sykes, an infectious diseases researcher at the University of California Davis School of Veterinary Medicine.

A mixture of pathogens could instead be to blame, experts now say. A new bacterium or virus could be among them, but it’s unlikely to be the only or main contributor.

Tests for known pathogens such as canine parainfluenza virus or Bordetella bronchiseptica have come up negative, but by the time the dogs make it to a clinic, they are likely to have stopped shedding the pathogen (or pathogens) responsible for their illness. The uptick in severe kennel cough may be due to a “perfect storm” of factors, Sykes and several others argue.

Dog ownership has increased recently. The fraction of American households with at least one dog grew from 38 to 45 percent between 2016 and 2022, largely during the COVID-19 pandemic. Today, more than 65 million families now have dogs. At the same time, rates of vaccination have dropped for a variety of reasons, experts suspect, making pets more susceptible to disease.

Now, as employees return to the office and families travel for the holidays, pet dogs may increasingly end up spending stints in kennels and doggy day cares. Pathogens of all kinds can spread easily in those group settings, creating a nasty soup that poorly timed or poorly executed swabs may miss. Hiskey suspects her dog caught a bug at the dog park.

What are scientists doing to solve the mystery of this illness?

Veterinary diagnostic laboratories in Oregon, New Hampshire and Colorado are currently examining swabs collected from dogs with atypical kennel cough, but they have not reached definitive conclusions.

Researchers from the University of New Hampshire in Durham have found a previously unknown bacterium in a majority of 70 samples collected from dogs stricken ill in New Hampshire, Massachusetts and Rhode Island. But they have yet to grow the bacterium in the lab, or to test the idea that it’s a driver of disease, a notice on the lab’s website says.

The UNH researchers could not detect the organism in tissue samples collected from dogs in 2018, long before the outbreak, but such a finding does not clarify the role the mystery bacterium plays — or does not play — in disease. The organism could be innocuous, or could worsen preexisting illness, rather than cause it.

The researchers are now examining more recent samples collected from Oregon, Colorado and other Midwestern states to see if they contain the bacterium, too.

What can dog owners do to protect their pets?

Keeping pets up-to-date on their vaccinations can reduce the risk of kennel cough.

Limiting interactions with other dogs, particularly those that may be ill, can help as well. Outbreaks tend to cluster in dog kennels, day cares and parks — places where animals crowd together. There’s no reason to panic, experts say, or to dramatically alter plans. Small precautions should suffice.

If your dog does exhibit symptoms, particularly those that do not improve with time, it’s best to call your veterinarian.

Saima Iqbal was the fall 2023 science writing intern at Science News. She holds a bachelor’s degree from Harvard College, where she studied the history of medicine, conducted research on cancer immunotherapies, and fell in love with narrative science writing.

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