Tan French bulldog lying on its belly on the carpet

Possible Increase in Upper Respiratory Illness in Dogs

A possible increase in upper respiratory illness in dogs (canine infectious respiratory disease complex [CIRDC]) has been reported from multiple locations across the United States in the second half of 2023. Clinical signs have been similar to those caused by a variety of common CIRDC pathogens such as parainfluenza virus and Bordetella, with cough and discharge from the eyes and nose. However, concerns have been raised about an unusually long duration of illness (3 to 8 weeks) in some affected dogs (the typical duration is 1 to 2 weeks). Although concerns have been raised about a potentially novel cause, such as a mycoplasma-like organism identified by researchers at the University of New Hampshire, it is also possible that no new pathogen is present, and instead illness is due to one or more known pathogens that are circulating and causing disease because of increased contact among dogs.

Since many respiratory pathogens can be found in healthy dogs as well as sick dogs, it can be challenging to make conclusions about causation, and often signs of respiratory disease ultimately result from multiple pathogens working together (an analogy is children in day care situations that develop respiratory illness due to multiple pathogens). In addition, our tests for these pathogens (which are usually based on PCR) are often falsely negative because organisms are shed intermittently, the swab samples we collect are small, they can be from sites where pathogens are not shed, and there can be degradation of the sample during transport to a laboratory. Dogs often don’t respond to antibiotic treatment because so many of the organisms that cause CIRDC are viral.

Over the course of the pandemic, dog ownership increased, and it is estimated that about 50% of households have at least one dog. As people have returned to work, and with travel over the holiday period, it is likely that there are more dogs being boarded, placed in dog “day care” facilities, and dogs are being looked after by other people that also have dogs. While the possibility of a new pathogen can’t be ruled out, it is also possible that increased respiratory illness is the result of these circumstances, and that disease may be more severe or prolonged because of co-infections with multiple organisms. Because respiratory illness in dogs is not tracked through reporting, it is not clear whether this represents a true epidemic or whether social media activity has contributed to what is known as an “infodemic.”   

Owners of dogs that contact other dogs in the community should be aware of the existence of CIRDC and be proactive to reduce the chance that their dog develops illness.

  • Ensure your dog(s) are vaccinated against the pathogens for which vaccines are available (Bordetella, parainfluenza, influenza H3N2, canine adenovirus, and distemper), as well as other infectious diseases for which vaccination is recommended.
  • If you must board your dog(s):
    • Ensure your dog(s) are vaccinated at least one week before entering the facility.
    • Use reputable facilities that practice good hygiene, do not board large numbers of dogs simultaneously, and that require proof of vaccination for Bordetella, parainfluenza, distemper, hepatitis, parvovirus, H3N2 influenza virus, and Leptospira with a booster at least one week in advance of boarding.
  • If you adopt a dog from a breeder or shelter, keep it away from other dogs for 2 weeks to make sure it does not break with respiratory illness, which could then be transmitted to other dogs in the community (or other illness such as diarrhea). Choose to purchase dogs from North America rather than importing a dog from another country where different pathogens may be circulating. The stress of importation can also contribute to increased severity of illness.
  • If your dog develops signs of respiratory illness, keep it away from other dogs for at least 2 weeks, and ideally until signs have ceased. If your dog has respiratory signs and is lethargic or eating less, contact your veterinarian and let them know if there is a possibility your dog has a contagious respiratory disease. They will then take appropriate precautions to minimize transmission in the waiting room and other parts of the hospital should hospitalization be required.
  • Remember there are other causes of respiratory signs that are not contagious, like fungal disease, heart failure, migrating plant awns, and cancer, so do not assume that your dog has CIRDC if your dog develops illness. Your dog should be evaluated by a veterinarian if signs persist more than a few days or are getting worse, and as soon as possible if your dog is lethargic or not eating.

There has been no association made between this illness and illness in other animals or people.

Additional information and resources are available here.

This entry will be updated as new information becomes available.

*This article may not be reproduced without the written consent of the UC Davis School of Veterinary Medicine.

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