Canine infectious respiratory disease has always been somewhat complicated but has suddenly become significantly more complex as we see apparent “outbreaks” of respiratory infection that seem much more severe than our usual pattern. CIRD, as we recognize it, can result from multiple organisms, and occasionally more than one is present during any particular episode of illness. The list at the end of this article shows all of the known organisms that have been associated with CIRD but the ones that we see most commonly when we test with PCR are Mycoplasma cynos, Bordetella bronchiseptica, and Canine Influenza (two strains). To add further confusion, some common infectious organisms can often be detected in perfectly healthy dogs, and this has been verified in multiple studies of well animals in various locations. <Links at end of article>
These infectious agents remain active and many dogs who present with typical upper respiratory symptoms will be suffering from one or more of these pathogens. In a normal, healthy dog, the majority will recover relatively easily and often with no involved treatment. CIRD, previously known as “kennel cough complex,” typically affects dogs of all ages and typically presents with a dry, hacking cough. However, despite this nasty-sounding cough, the pet remains active and alert and often continues to eat fairly normally. The cough may worsen with activities like barking, exercising, or being excited. Some of these dogs may require treatment for the cough or coinfections. It is advisable to isolate them, as they will likely be contagious for a few weeks depending on the specific organism(s). It is important to note that a small percentage of dogs may become seriously ill, especially those who are very young, old or have a weak immune system.
What we are seeing since midsummer in Oregon is a vastly different patient profile. There are 3 common presentations:
typical symptoms of upper respiratory infection with a prominent cough, but the cough does not resolve and becomes chronic (weeks to a few months) with little or no response to antibiotics
upper respiratory symptoms that progress to bronchitis or bronchopneumonia which, while not life-threatening, remain chronic and poorly responsive to antibiotics and may persist for weeks to a few months
an acute syndrome in which the hallmark is rapidly progressive pneumonia that is also poorly responsive to antibiotics. In the acute syndrome, the patients can become desperately ill in just 24 to 36 hours after the initial cough.
Clearly, the dogs that are presenting in these 3 categories are very different from what we are accustomed to in our patients with CIRD. There are scattered reports of similar respiratory outbreaks prior to Oregon, possibly as long as a year ago, and a few different geographic locations have been reported.
Multiple laboratories are at work trying to isolate the organism or organisms that may be the cause of this new outbreak. Early information from the New Hampshire veterinary diagnostic lab suggests this may be a very tiny bacterium that does not culture readily and is being identified via DNA sequencing. It has not been isolated sufficiently even to permit characterization of the bacterium.
As expected with any newly recognized organism, there is no test to determine its presence nor a clear treatment protocol that is consistently successful. Some dogs that have been quite sick over the last 3 to 6 months have tested positive for more traditional agents such as Canine Influenza virus, and Mycoplasma cynos. As noted earlier, dogs can be completely asymptomatic and healthy and still carry some of these respiratory organisms, which will trigger a positive PCR test. Multiple studies have determined that normal healthy dogs are often colonized with one or more of these infectious species that are known to cause respiratory disease in susceptible pets.
Given how early we are in this process, accurate testing will not become available in the near future and immunizations to protect our pets from this organism will take even longer. Since respiratory organisms often work in concert, it is imperative that we prevent infection with our known respiratory agents as much as possible. Influenza vaccines for dogs, like humans, are designed to reduce the severity of the disease but will not necessarily prevent infection 100%. We do know that the presence of canine parainfluenza virus can significantly increase the severity of infection with other agents as it causes damage to the lung tissue directly.
We can, and should, vaccinate our susceptible population to try to reduce the risk of Bordetella bronchiseptica, canine parainfluenza virus, and canine influenza viruses. Combined with the new infectious agent, any of these would undoubtedly worsen the outcome. The veterinary labs that are attempting to research this organism are requesting that samples be provided directly from the veterinary hospitals prior to the initiation of any medications as they may reduce the ability to culture this suspected bacterium.
Given that some dogs are becoming severely ill very quickly, it is also recommended to have these animals examined very early in an attempt to intervene before the pneumonia becomes severe. PCR testing is still recommended as many dogs that are presenting with canine cough and respiratory symptoms actually still have one of the better-known organisms that cause respiratory disease. PCR testing is most accurate early in the disease. Delays can cause false negative results. Co-infection will still be a concern if the PCR is positive and the dog is severely ill or presenting with one of the three syndromes associated with this new infection.
Canine respiratory outbreaks tend to wax and wane and pop up in different locations from time to time. There are often isolated but significant outbreaks of respiratory disease in relatively small geographic areas that then move to another area, causing a different outbreak. This has been happening for years but without the severity of the outcomes seen in this current small population, who are affected much more gravely than expected historically.
In summary, if indeed there is a new organism causing these outbreaks, isolation of this new organism may prove difficult, and the ability to test for it specifically is probably long in the future. Dogs presenting with respiratory symptoms should be examined and treated as early as possible during the disease. PCR testing done early can still be informative and should be performed. Since co-infection may worsen the prognosis, it is recommended to ensure all dogs are current on their Canine Parainfluenza, Bordetella bronchiseptica, and canine influenza immunizations.
The assumption is this organism is probably airborne but may also be carried from dog to dog by fomites which includes potentially grooming tools, leashes, collars, and probably direct human contact. When possible, avoid areas where unfamiliar dogs tend to congregate, such as dog shows, canine sporting events, dog parks, doggie daycare, boarding and grooming facilities. These are areas where you are most likely to encounter dogs of unknown health and immunization status.
Dogs you know personally, their health, immunization status and recent travel or exposures, are often relatively low risk by comparison. Watch the local news for any indication that the infection has reached your local area. While it may not always be practical to isolate your pet from all other dogs, attempt to reduce direct contact with unfamiliar dogs and sanitize your own hands carefully after touching any other dogs. If your pet is sick with a cough, please call your veterinary hospital before arriving and they will advise you on protocol to help prevent exposure to the other pets in the facility. If your dog has been ill with respiratory symptoms, the current recommendation is a minimum of 3-4 weeks isolation from other dogs.
It is likely that we will gain much more information in the coming months, but concrete answers may require patience if this truly is a new organism not previously isolated and described.
The current list of known canine respiratory pathogens:
Viral pathogens include canine distemper (CDV), parainfluenza (CPIV), adenovirus type 2 (CAV-2), influenza (CIV, two strains), herpesvirus (CHV-1), respiratory coronavirus (CRCoV), pantropic coronavirus, reovirus, and pneumovirus (CnPnV). Other emerging viral pathogens associated with CIRD are canine bocavirus, hepacivirus, and picornavirus.
Bacterial pathogens include Bordetella bronchiseptica, Mycoplasma spp., and Streptococcus equi subsp. zooepidemicus.
For more information on this rapidly changing situation: