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What’s Causing Mysterious Respiratory Illness in Dogs?

Veterinarians and researchers are investigating mysterious clusters of severe respiratory disease in dogs

A severe respiratory illness appears to be spreading in dogs in at least 15 states, according to recent reports. Veterinarians compare it to “kennel cough,” a term used to describe several viral and bacterial infections that can cause a sudden, honking cough in dogs. But whereas kennel cough usually clears up, the recent infections have resulted in pneumonia and even death. One research team has pinpointed a bacterium with an odd genome as a potential source.

“In some of these places the dogs that are affected are more severely affected than what we would normally experience” in a typical respiratory season, says Kathleen Aicher, a veterinarian who specializes in internal medicine for dogs and cats at Texas A&M University. “Even if that’s a fairly isolated thing, for the veterinarians who are seeing those dogs and for the families that love those dogs, that is pretty darn scary.”

While plenty of dogs seem to clear the infection with treatment, others aren’t responding to typical treatments and develop long-term symptoms or secondary infections, Aicher says. Some of these dogs can deteriorate frighteningly quickly. She points in particular to reports of cases in which vets have needed to put dogs on ventilators or to surgically remove sections of infected lung tissue—both of which are extremely unusual measures—particularly for dogs that had previously been young and healthy, as some of these are, Aicher notes. “In the areas of the country that are reporting this right now, they’re really going through a difficult time,” she says.

Although the mysterious illness is now making headlines nationally, cases remain patchy, with reports coming from the states of Oregon, Colorado, California, Illinois, Florida, Georgia, Indiana, Massachusetts, Washington, Vermont, Maryland, Idaho, New Hampshire, Rhode Island and Pennsylvania. That said, it’s not yet clear whether the same infection is responsible for all these cases, Aicher says.

Veterinary investigators are having trouble tracking down the organism—or organisms—responsible for these strange illnesses, says David Needle, a veterinary pathologist at the New Hampshire Veterinary Diagnostic Laboratory and a clinical associate professor at the University of New Hampshire, who since late 2022 has led the process of trying to identify the cause of infections in New Hampshire.

He first heard about the illness last year, but in the early days, he had no samples—neither nasal swabs nor affected tissue—to analyze, a situation he found quite frustrating. “There were questions and no ability to generate the data,” Needle says. He ended up driving sampling kits out to several vets at the time; his team is now receiving samples from a wider range of states, including Oregon, which was hit particularly hard beginning in August of this year.

 Veterinarians say fears about 'mystery' dog illness may be overblown. Click NPR logo

The investigation has been slowed partly by a lack of funding. “In human medicine, if this were to happen, there are millions of dollars to throw at it right away,” Needle says. “We don’t have that, and so that does slow us down a bit. We have to be more selective in how we perform the investigation.”

In addition, the infectious agent Needle and his colleagues are tracking doesn’t seem to be closely related to known pathogens, and it can’t be cultured in the lab. “If it were just like a new flavivirus [a class of virus that can cause diseases such as yellow fever and dengue in humans] or a new influenza or something like that, that would have been ‘bing, bang, boom’—it would have been [identified in] a couple weeks,” Needle says. “But since it’s weird, it took some digging.”

After months of work the researchers have found a bacterium that they’re beginning to think is the culprit. It’s a small bacterium that boasts a genome unusually rich in the DNA “letters” adenine and thymine and poor in cytosine and guanine—which is atypical for most organisms, Needle says. The bacterium also seems to be missing key genes that would allow it to survive on its own in the environment, he notes, which suggests it can live only within hosts.

The team is continuing a range of tests, including on new samples. Needle says he hopes his team will be able to confirm the identity of this mysterious pathogen within the next three to six weeks as sequencing and other testing continues.

The last significant new dog pathogen that veterinarians identified was canine influenza virus in 2004. “For me personally, it’s been really cool and horrible at the same time,” Needle says of the newly identified pathogen.

Even without knowing exactly what’s causing the illness, you can help keep your dog safe. Most important is to be sure dogs are up to date on all the recommended vaccinations. “While the existing vaccines may not specifically target this unknown infection, maintaining overall health through routine vaccinations can help support a dog’s immune system in combating various infections,” Rena Carlson, president of the American Veterinary Medical Association, said in a statement.

“Owners should monitor their dogs closely for progressive coughing that may be accompanied by signs of ocular or nasal discharges and sneezing,” she said, adding that the situation is particularly concerning if a dog also “loses its appetite, has trouble breathing, is coughing continually or is extremely lethargic.”

Aicher reminds dog owners not to bring their pups to kennels, doggy day care facilities, dog parks or other crowded situations if they seem sick. And if you need to take a coughing dog to the vet, call ahead and offer to wait in the car or bring your pet in through a different entry to avoid exposing other pets, she says.

Your local vet could also let you know if the new illness appears to be active in your region, Aicher says. If it is, owners can consider taking additional steps such as hiring a dog sitter instead of boarding their pup.

But in general she says that owners shouldn’t panic about this illness. “For the majority of people in the country, if they’re not in an area that’s having a known outbreak, I think that it’s life as usual, with just making sure that we’re doing all the things that we should have been doing all along,” Aicher says. “We can’t live in fear all the time.”


MEGHAN BARTELS is a science journalist based in New York City. She joined Scientific American as a news reporter in 2023. Previously, she spent more than four years as a writer and editor at, as well as nearly a year as a science reporter at Newsweek, where she focused on space and Earth science. Her writing has also appeared in Audubon, Nautilus, Astronomy and Smithsonian, among other publications. She attended Georgetown University and earned a master's in journalism at New York University's Science, Health and Environmental Reporting Program.



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