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Respiratory disease: Pair up for protection

dvm360dvm360 May 2021
Volume 55

A growing number of veterinarians endorse the idea of vaccinating against both canine infectious respiratory disease complex and canine influenza virus. Here’s why.



The analogy isn’t perfect, but it’s close. The human medical community intensely encouraged individuals to receive the influenza vaccine before the COVID-19 vaccine became available. Getting sick with COVID-19 could be bad enough, they reasoned, but getting COVID-19 and influenza could be insurmountable.

Similarly, a growing number of veterinarians, including Natalie Marks, DVM, CVJ, assistant medical director at VCA Blum Animal Hospital in Chicago, endorse the idea of pairing up for protection against both canine infectious respiratory disease complex (CIRDC) and canine influenza virus (CIV).

“It’s human nature to think, ‘I’m not seeing it, so it must not be a problem,’ ” says Jenifer Chatfield, DVM, DACZM, DACVPM, a Tampa, Florida, veterinarian, and member of the dvm360® Editorial Advisory Board.

Marks was at ground zero in Chicago for the H3N2 outbreak in dogs in 2015-2016. “Living through that is something I will never forget. Of course, we had no available vaccine. How could we? But we do now,” she says.

Not your grandmother’s Bordetella

The CIV mortality rate is only 2% to 4%, according to Marks, but morbidity is at 98% with a wide array of clinical signs. Also, this is no longer your grandmother’s Bordetella. It is now known as CIRDC, which is far more representative of what
this typically is—a cocktail of respiratory illnesses.

“When it comes to respiratory disease, compounding infections is the enemy,” says Julie Reck, DVM, owner of Veterinary Medical Center of Fort Mill in South Carolina. “This means that infection with specifically Bordetella or canine influenza is likely self-limiting in most pets. They may be mildly symptomatic and typically recover on their own, with little to no treatment. But this changes drastically if they succumb to multiple infectious agents, and this reality is unfortunately very common in respiratory disease.”

According to a 2019 study published in PLoS One, Mycoplasma cynos is an emerging bacterium that is increasingly implicated in CIRDC and most commonly identified in symptomatic dogs.1 The investigators found a significant association between the presence of M cynos and the development of moderate clinical signs. M canis, according to the study, is also on the rise.

The occurrence of traditional CIRDC agents, such as Bordatella bronchiseptica, was surprisingly low in the study.1 Conjecture is that years of vaccination likely won that war, but there are always new pathogens ready to infect.

According to Marks, testing for respiratory disease is important for several reasons:

  • Some agents, such as Mycoplasma and Streptococcus, are bacterial
    in nature. The correct course of treatment could be missed.
  • CIV goes unrecognized, although it’s not known how often, because the infection is commonly assumed to be Bordetella and no testing is completed.
  • Zoonosis is a real possibility.
  • Looking for coinfection matters.

In the PLoS One study, the greatest predictor of moderate to severe clinical signs was coinfection.1 Also, young dogs generally have increased susceptibility to CIRDC.

“For any vaccine, it’s lifestyle and potential zoonotic transmission that matter most, right?” Chatfield asks. “Think about the lifestyle concerns and risks that lead you to say, ‘Yes, vaccinating for Bordetella makes sense.’ Well, it’s the same lifestyle and risks for CIV, so why wouldn’t you vaccinate for both?”

“There is no way to say this nicely, but I’m not letting a boarding facility, one that says dog flu isn’t important, inform my guidance on vaccine decisions,” she adds. We’re learning every day about how prevalent coinfections are and how they can cause more severe diseases. Do you wait for an outbreak or prevent a problem in the first place and be part of the solution?

“Also, I suggest that as we see more parainfluenza and Mycoplasma—so many pathogens—we may learn that CIRDC is impacting at least some dogs more than we might have suspected,” Chatfield continues. “In any case, I don’t feel this is an innocuous kennel cough.”

“We know respiratory disease can cause a wide range of clinical signs, some of which require hospitalization,” Marks says. “Even when dogs don’t require hospitalization, their quality of life is very obviously affected, and the same is true for pet parents.” With about half of all dogs sharing their owner’s bed,2 a coughing dog may keep an entire family awake.

Toward herd immunity

Pairing up for protection is a way to effectively move toward herd immunity, “I know we all learn about herd immunity in veterinary school, and we may have thought it applies only to our large animal colleagues,” Marks says. “It applies to us in small animal medicine equally. We want to further protect our patients, protect the community, and protect ourselves.”

Chatfield notes, “There is now a novel influenza among pigs in China that has the capability to infect people. We also know dogs in China have already been coinfected with multiple strains of flu simultaneously.”

As everyone is experiencing on the human side, viruses will happily mutate, given the chance, and conceivably jump species, as H3N8 did from horses to dogs.

“I don’t even want to imagine a scenario if dog flu were to become transmissible to people,” Chatfield says.

“Our job is preventing disease,” Marks concludes. “If we let them catch disease and then play catch up and treat, that’s not doing our job."


  1. Maboni G, Seguel M, Lorton A, Berghaus R, Sanchez S. Canine infectious respiratory disease: new insights into the etiology and epidemiology of associated pathogens. PLoS One. 2019;14(4):e0215817. doi:10.1371/journal. pone.0215817
  2. APPA National Pet Owners Survey, 2019-2020. American Pet Products Association; 2019:92.

Steve Dale, CABC, writes for veterinary professionals and pet owners, hosts 2 national radio programs and has appeared on TV shows including Good Morning America and The Oprah Winfrey Show. He is on the dvm360® Editorial Advisory Board as well as the boards of the Human-Animal Bond Association and EveryCat Foundation. He appears at conferences around the world. Visit stevedale.tv.

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