Canine infectious respiratory disease complex (CIRDC) is a term we use to describe a variety of clinical respiratory illnesses in dogs that have an infectious etiology at their core. These include common viruses, such as adenovirus, influenza, and parainfluenza, as well as bacteria, such as Mycoplasma cynos, Bordetella bronchiseptica and Streptococcus equi subsp. zooepidemicus (S. zooepidemicus).

It is important to keep in mind there is a baseline of these respiratory illnesses in our canine populations, and we routinely see small outbreaks when dogs are housed together in shelters or kennels, or are interacting closely in dog parks or daycare settings.

Since there is no standard surveillance system for dogs, we tend to hear about these outbreaks on and off as they occur and either make the local news for one reason or another, or when they become larger regional outbreaks, similar to the H3N2 virus in Southern California in 2021.

So, the question for 2023 was, “Did we have some type of national outbreak?” The answer is likely not. Generally, an outbreak of infectious disease would have an initial location and then would spread based on movement of the ill animals or contact with the initial source animals. For example, in the Southern California outbreak, originally dogs were getting ill in Los Angeles County with a point source identified as an imported dog, and the disease then spread to adjacent counties Orange, Riverside, and San Bernardino.

Recently, we have heard about small groups of dogs in various states across the country becoming ill with respiratory disease. Most have been in group settings. Most have gotten better. Some have confirmed diagnoses based on available testing. A few have had a more serious aggressive disease course. All of these are common situations. However, there does not appear to be a broader epidemiologic event going on.

This is not to say there are not both viruses and bacteria causing respiratory illness in dogs we currently do not or cannot yet diagnose, or that there are not newly emerging causes of disease. For example, the research recently shared out of the University of New Hampshire evaluated samples from 31 dogs with similar clinical disease syndromes that had negative PCR tests.¹ According to the report, “21 of 31 samples were found to have segments of DNA that are predicted to belong to a likely nonculturable bacterium that is most similar to a pathogen reported in association with respiratory disease in people in 2021.”² They were clear in their published findings, however, that the information was preliminary, that the organisms may be commonly host adapted, that neither correlation nor causation was yet confirmed and additional research would be necessary.

Los Angeles County Veterinary Public Health issued the following statement regarding the possibility of a respiratory syndrome that is, as of yet, undiagnosed:¹
“This respiratory illness is currently known as atypical canine infectious respiratory disease (aCIRD). Cases are currently defined as having a negative canine respiratory PCR test panel, which tests for common viruses and bacteria identified in dogs with similar symptoms, plus one of the following clinical scenarios:

Chronic mild-moderate respiratory infection that lasts more than six weeks that is minimally or not responsive to antibiotics;
Chronic pneumonia that is minimally or not responsive to antibiotics; or
Acute pneumonia that rapidly becomes severe and often leads to poor outcomes in as little as 24-36 hours.

Scott Weese, DVM, DVSc Guelph; Dipl. ACVIM, professor at the University of Guelph Ontario Veterinary College (OVC), put it best in a quote from a recent American Veterinary Medical Association (AVMA) update on the subject: “By that, I mean that it’s more likely that it’s a longstanding cause of disease that we’ve never diagnosed before, versus a new bug that’s recently emerged and is starting to spread,” Dr. Weese wrote. “The current disease patterns don’t really fit with emergence of a new highly transmissible pathogen.”³

So, what strategies should we employ as veterinary professionals to both care for our patients and help our clients and communities? First, do not contribute to the panic. Focus on evidence-based diagnostics, treatments, and preventive measures.

We have PCR tests available for the most commonly known pathogens, so completing diagnostics can help us provide both appropriate treatment and isolation recommendations to prevent spread.

Let clients know diagnostics are important so you can recommend the correct treatments. Help them understand that just “guessing” could result in a longer disease course, providing the wrong drug, or giving one that causes unnecessary side effects. For patients with milder disease, manage symptoms as needed, generally do not use antibiotics, and keep the patients isolated for three to four weeks. The International Society for Companion Animal Infectious Diseases (ISCAID) Respiratory Guidelines are a helpful tool for disease management.⁴

While trans-tracheal wash and bronchoalveolar lavage are challenging, they are indicated in patients that are suspected to have pneumonia and are showing more serious clinical signs, to ensure we are choosing the correct antibiotic to treat them.

Vaccinate for the respiratory diseases that we can, including using the bivalent canine flu vaccine (H3N2/H3N8) and a triple intranasal respiratory vaccine covering adenovirus, parainfluenza, and Bordetella. There appears to be enough historical data on canine respiratory disease to support the likelihood that dogs with multiple pathogens tend to have more serious illness so we should prevent what we can.

What else can we do? We can keep our hospitals safe by employing a variety of standard preventive precautions. Consider having specific operating procedures for the following areas:

Cleaning and disinfection

Use of accelerated hydrogen peroxide products is a good overall recommendation.
Clean before disinfecting – remember they are not the same thing. Cleaning removes debris while disinfecting removes/kills organisms. This applies to shared items such as bowls, cages, doors, floors, tables, grates.
Hand hygiene involves washing hands between every patient, between touching a patient and touching other objects, including computer keyboards, cell phones or equipment, wearing gloves where contact may occur with vomit, feces, urine, infected tissue, and washing hands after glove removal

Respiratory intake policy

Ensure the customer service team asks clients if pets are having respiratory signs, and if so, letting them know to call upon arrival to check in and not to bring the pet inside.
Once pets arrive, contact the technical team to determine if the patient is more likely having respiratory signs due to known illness (asthma, heart disease) or infection (recent history of boarding or day care).
Wear proper PPE for handling respiratory patient intake (gloves and gowns are recommended) and use a separate intake location (exam room or outdoor area if fenced and outdoor temperature is appropriate). Never examine pets in cars or the parking lot.

Silene St. Bernard, DVM, DACVPM, has over 25 years of experience in companion animal veterinary medicine. She is currently a regional medical director for VCA Animal Hospitals in Southern California. Dr. She is a member and former chair of the board of Health and Human Services for the City of Long Beach, CA, and is a past president of the American Association of Industry Veterinarians (AAIV).

References

Needle, David; Respiratory Syndrome of Unknown Etiology in Dogs 2022-3 in New England: Diagnostic Investigation; University of New Hampshire/New Hampshire Veterinary Diagnostic Laboratory
http://publichealth.lacounty.gov/vet/
https://www.avma.org/news/making-sense-mystery-illness-found-across-us
Antimicrobial use Guidelines for Treatment of Respiratory Tract Disease in Dogs and Cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases; J Vet Intern Med 2017;31:279–294.