What is Causing Severe Respiratory Illnesses in Dogs?

Veterinarians across the United States are scrambling to diagnose and treat the rising number of dogs ill with a severe type of respiratory illness. Simultaneously, scientists are trying to figure out what is behind the current outbreak, how widespread it is, and how many pups that were previously healthy have become seriously sick or died.

One example of a previously healthy dog happened to a young Australian shepherd, only seven months old, when she began coughing. Her owner became frightened when the puppy’s cough progressed rapidly, keeping her owner up at night.

The young dog was tested for numerous illnesses at the vet the following day, and all returned negative.

The vet later contacted the owner, who said that since there is no definitive proof of illness yet, it is still unknown what is causing it.

The puppy was treated for bronchitis, given a steroid shot and nebulizer, and had the lung secretions cleared. She was also sent home on two different antibiotics.

Canine respiratory infections, especially canine flu, are common and often cause outbreaks in doggy day care and shelters. The surge has continued to spread in Canada and the U.S. over the past year. 

The outbreak differs from common respiratory illnesses, say experts, because of the many cases severe enough to lead to pneumonia.

In Colorado, the number of canine pneumonia cases rose by 50% this year from September to November, compared to the same months in 2022, said Dr. Michael Lappin, infectious disease expert and director for the Center for Companion Animal Studies at Colorado State University School of Veterinary Medicine.

According to pet insurance company Trupanion, claims data suggests the number of canines with severe respiratory illness continues to rise in several states.

More dogs are getting increasingly ill because they’ve been infected with several pathogens at the same time — including Bordetella (kennel cough), canine influenza, and mycoplasma pneumonia — said section chief of emergency medicine and critical care at the Ryan Veterinary Hospital at the University of Pennsylvania, Dr. Deborah Silverstein — similar to the tripledemic of influenza, RSV, and Covid-19 that affected people last winter and fall.

Is this a new illness?

There could be numerous reasons for the uptick in cases. Several dogs may have lower infection resistance because restrictions from the pandemic kept them out of boarding facilities or daycares, and they weren’t exposed to circulating bacteria or viruses, note experts. There have also been decreases reported in canine vaccination rates. A recent research study found almost half of dog owners are hesitant about vaccinations and their pets.

“We’ve got more dogs that have a lower level of resistance because they’ve been exposed less over the last couple of years and they’ve had less vaccination,” said infectious disease veterinarian at the Ontario Veterinary College, Dr. Scott Weese, during a Thursday online briefing. “So that means just with our normal respiratory disease that’s always there and always circulating, we can see more disease and more spikes.”

Silverstein said it is possible that any of the factors could explain the disease’s increased incidence, making some dogs deathly sick.

“It’s more than likely that some buy may have changed its virulence,” said Silverstein. “Just like Covid strains can be milder or more severe.”

But, there is a possibility there is a new circulating bacteria.

University of New Hampshire scientists recently identified a novel bacterium as the possible culprit. The findings are based on a minute number of cases from states in New England, so the results need to be confirmed in a more substantial and geographically diverse sample of dogs.

Researchers at other centers, including Colorado State University, the University of Pennsylvania, and Oregon State University, are also attempting to identify the outbreak’s cause.

One significant factor slowing down research in the United States is that there is now a single group tracking pet illnesses. For example, CSU scientists are coordinating with the U.S. Department of Agriculture, the state veterinarian’s office, and other researchers to get additional insight into what is happening in Colorado.

An additional hurdle is that many owners need help to take an ailing dog to a veterinary hospital or specialist or even pay for diagnostic testing. According to the chief veterinary officer at Trupanion, Dr. Steve Weinrauch, “For less frequent, but severe cases where multiple day hospitalization and supportive care is necessary, costs can range from $15,000 to $20,000.”

Which dogs are at higher risk?

Usually flat-faced or brachycephalic dog breeds, including pugs and French bulldogs, dogs with underlying lung disease or senior dogs are more at risk of developing pneumonia stemming from a respiratory infection.

However, at Texas A&M School of Veterinary Medicine, Dr. Kate Aicher treated a group of cases of canine respiratory disease in vaccinated young dogs in March and April of this year. Aicher and colleagues were seeing a wide range of severity and a sudden onset of fever.

“You don’t expect 1- and 2-year-old dogs who are well conditioned and healthy to end up with pneumonia so severe that they need to be put on a ventilator and then die,” Aicher said. “You don’t expect dogs to die despite aggressive care.”

Around 75% of the canines at Texas A&M tested positive for a known pathogen. However, in 25%, there was nothing on all the tests, said Aicher.

For Aicher, it suddenly became personal. Her young Labrador retriever developed a disturbing cough and a high fever. The dog was hospitalized and recovered with treatment. Her pup is now home, “running around being her normal Lab self.”

Sadly, Aicher said a canine of the same breed and age that came to the hospital for treatment didn’t make it.

She recalled that her dog had coughed once on a walk and made some subtle snuffling noises. 

“In hindsight, those were probably the first signs, and they didn’t trigger any alarm bells,” said Aicher. Her experience underscores the importance of owners knowing their pets and recognizing when things seem off.

Canine respiratory infection symptoms include:

• Runny, red eyes.

• Sneezing.

• Coughing.

Several dogs will recover on their own. But if the dog has breathing difficulties or stops eating, it could be a more severe problem, and the dog must be taken to a vet.

With all the attention the unidentified sickness is getting in the media, particularly on social media, the chair of shelter medicine at the University of Florida College of Veterinary Medicine, Dr. Cynda Crawford, worries the owners will panic when there aren’t many overall cases.

Nonetheless, “vets working on the front lines in private practice are seeing higher numbers of dogs with respiratory illness, and some of those dogs are progressing to pneumonia,” said Crawford. “They are reporting that the dogs are not responding as well or as quickly to the normal standard of care.”