‘Hacking’ Kennel Cough: Shelter Medicine Insights for our Canine Respiratory Woes

A Blog by CASCMA Board Member, Dr. Hannah Weitzenfeld, DVM

Mystery US Canine Respiratory Illness

With the recent apparent increase in Canine Infectious Respiratory Disease Complex (CIRDC) in community and shelter dogs across the US₁, many of us are looking at what could be causing this, and how we might approach a severe outbreak in our shelters. While an individual causal pathogen has not been identified and experts generally attribute the cases to our usual suspects₂, post-pandemic increases in dog populations in shelters, and an increased length of stay_3,14 are likely playing a role in shelter outbreaks. CIRDC is the most common cause of illness in shelter dogs, with length of stay being the most significant risk factor, and each day in shelter care has been shown to increase a dog’s risk of CIRDC by 3%₄.

Epidemiology in the US and Canada

Based on Canadian data of the proportion of respiratory illness claims from Trupanion, there has been a gradual increase of 60-70% in these claims over the last 3 years. Comparing the August-October period between 2022 and 2023, some provinces showed significant increases, including Quebec at an alarming 70.7%, Nova Scotia 32.7, Ontario 25.2% and British Columbia at a distant 6.2%₅. While the type of respiratory illness is not specified and insured animals represent a biased data set with many unmapped factors which require evaluation, these changes are compelling and merit ongoing observation.

Regarding specific CIRDC pathogens, many are commonly found in both Canada and the US, such as Bordetella bronchiseptica, Mycoplasma cynos, and canine respiratory coronavirus. However, patterns of CIRDC pathogens can change over time.

Canine influenza is a highly contagious viral cause of CIRDC that is seen fairly frequently in the US₆, but is not endemic in Canada. With this pathogen, exposed dogs tend to get sick simultaneously, and some may develop pneumonia. Until October 2023, Canine influenza hadn’t been documented in Canada since a 2018 Ontario outbreak from imported dogs which was quickly contained₁₆. In October of last year, a single case of canine influenza was identified in Calgary, Alberta_7,8. This case was associated with travel to the US, and fortunately, there was no transmission in this case. However, with dogs travelling frequently between the two countries, the risk of future cases or further spread is ever present.

Canine pneumovirus is a respiratory pathogen which has shown a reduction in virulence over time₃. When it was initially identified in 2010, canine pneumovirus resulted in a long course of disease and sometimes resulted in fatal pneumonia₉. The current disease pattern frequently seen is a highly contagious cough with lower virulence and a high attack rate. This pathogen has been linked to shelter outbreaks in both the US and Canada, as well as other countries. Canine pneumovirus can be detected by PCR, although shedding peaks early in the disease process. It is not included in all available respiratory PCR panels and is frequently missed₁₅.

Some American shelters are seeing an increase in acute, severe outbreaks of Streptococcus zooepidemicus over the past two years₂. This pathogen can cause both mild, chronic and severe, acute disease, with the latter causing hemorrhage in the lungs, and an increased risk of fatalities. It can also be part of a co-infection with viral pathogens, usually resulting in severe clinical cases₉.

An increase in canine distemper detections have been noted in some Canadian communities within the last two years_{11, 12}. Canine distemper is endemic in many parts of Canada, often affecting remote communities with reduced access to vaccination. Canine distemper can also affect wildlife, such as skunks and foxes. Its much less commonly detected in most Canadian shelters as compared to some states, such as California and Texas₅. Preventing the spread of CDV in the shelter can be challenging, as the long incubation period can result in other animals becoming infected before signs are apparent. Animals with CDV can also shed it for prolonged periods of time in some cases.

Shelter CIRDC Testing Approaches

Depending on the location, facilities, resources and population management of individual shelters, veterinarians may employ different approaches to testing.

In most cases, it is advisable to consider PCR testing in cases where

• there is significant spread of disease in care
• there are more dogs affected in the shelter than the expected baseline or
• the clinical presentation is more severe or of longer duration than normal

Because peak shedding occurs in the days before and after the onset of clinical signs, timing of testing early in the course of the disease is crucial₁₀.

The Canine Respiratory Real PCR panel from Idexx is generally the diagnostic of choice for CIRDC, as this is the most comprehensive panel, and there is a significant discount for shelters₁₀. This panel includes Bordetella bronchiseptica, canine adenovirus type 2, canine distemper virus, canine herpesvirus type 1, canine parainfluenza virus, canine pneumovirus, canine respiratory coronavirus, H3N2 canine influenza virus, influenza type A virus (includes H1N1, H3N8), Mycoplasma cynos, and Streptococcus equi subsp. zooepidemicus RealPCR tests.

When undertaking testing, sharing information on unusual pathogens identified through organizations like the Canadian Animal Health Surveillance System (CAHSS) can allow veterinarians to help each other to understand larger trends in CIRDC.

Canine Respiratory Real PCR Panel Interpretation

PCR is very sensitive and specific for pathogen presence, though thoughtful interpretation is required to determine which pathogens are significant. PCR cannot differentiate between vaccine and disease strains, and vaccines can cause positive results for several weeks after vaccination. For canine distemper, quantitation included with the Canine Respiratory Disease PCR Panel may raise the index of suspicion, and CT values can be requested from the laboratory for further analysis. In some cases, sequencing may be required for confirmation. Additionally, not all etiologies of CIRDC are included in respiratory panels, sometimes affecting negative results.

Asides from vaccination, another factor to consider is that some pathogens can be found in healthy dogs, so while they may be present, they may not be the cause of clinical signs.

In summary, the clinical signs, exposure history, vaccination history and the pattern of disease in the population, as well as pathogen patterns seen in results from a group of dogs are important elements to consider in the interpretation of respiratory PCR panels.

While results are unlikely to determine treatment in most individual cases, they can be instrumental for understanding the course of disease and management at a population level. Additionally, undertaking testing for surveillance allows an understanding the of the pathogens commonly encountered in a specific shelter, which can be helpful in development of shelter protocols for disease prevention and management.

Applying diagnostic information to case management – case example:

The BC SPCA Drive for Lives program transports 4000 animals each year from northern shelters to more populated areas in the south of the province, where they can be adopted, increasing the shelter system’s capacity to help more animals in northern shelters, where at-risk animal populations are greater and there are reduced human populations as potential adopters. While the program has excellent protocols to prevent infectious disease spread, CIRDC can still be a concern due to preclinical shedding and risk associated with long-distance transportation. Many shelters are small, community shelters with a limited ability to isolate dogs.

In November 2023, a puppy (Patient 0) was transferred and began exhibiting cough within 12 hours of the transfer. Given the preclinical shedding expected with these pathogens, this indicates that the other animals on the transfer were likely exposed. The affected puppy was isolated and all dogs from the transfer and those exposed to the affected dog at the shelter of origin were quarantined. Within 4-6 days, several other dogs exposed from this transfer also began exhibiting clinical signs.  PCR testing revealed the following:

Table 1. Canine Respiratory Real PCR positive results for initial case (patient 0), dogs exposed on transfer that became clinical (transfer1-4), and non-transfer dogs exposed at destination shelter C following transfer (secondaryC1-3). Bordatella bronchiseptica (Bord), Canine adenovirus 2 (CAV2), Canine distemper virus, (CDV), Canine Pneumovirus (CnPnV), Canine Respiratory Coronavirus (CRCoV), Mycoplasma cynos (M. cynos). Only pathogens with at least one positive result were included in the table.

This pattern was consistent with a coinfection of canine pneumovirus and canine respiratory coronavirus with possible secondary Mycoplasma cynos. While coinfections with multiple pathogens are common, and coinfection of canine pneumovirus and canine respiratory coronavirus has been documented in American shelters₈, this is an interesting pattern in our region, as canine pneumovirus has not been commonly detected in the BC SPCA shelter system. It is suspected that the positives for Bordetella bronchiseptica, canine adenovirus and canine distemper are secondary to recent vaccination. With the combination of canine pneumovirus and canine respiratory coronavirus, explosive shelter outbreaks can be expected, so a clean break is critical. Measures involved ensuring that animals could be promptly and appropriately isolated and quarantined, pausing shelter intake if necessary. Symptom monitoring vigilance was increased, and foster and adoptive pathways were prioritized. Increased frequency of cleaning was implemented to reduce fomite transmission. These measures resulted in relatively few animals becoming sick.

Preventative Strategies

Factors involved in exceeding shelter capacity for care, such as comingling and crowding, increase the risk of CIRDC in shelters. Other animal health and welfare-related factors, such as the ability to maintain positive welfare in the shelter, adequate air quality, staff capacity to carry out sanitation and biosecurity protocols appropriately, and the ability to vaccinate immediately upon intake are also components of shelters’ capacity for humane care that are critical in CIRDC prevention. 

Reducing length of stay by remaining within capacity for care and through other means, can go a long way in ensuring shelters can prevent significant outbreaks.

Additionally, appropriate treatment of bacterial cases can reduce the shedding period and risk to other animals. Because tetracyclines are effective against bacterial CIRDC pathogens Bordetella bronchiseptica and Mycoplasma cynos, doxycycline remains the treatment of choice for bacterial CIRDC₁₃. Infectious disease experts are now recommending doxycycline even in young animals, as evidence and experience indicate that the benefits outweigh the risks₁₇.

In conclusion, tackling CIRDC in shelters necessitates a nuanced population health approach. The evolving nature of this disease, coupled with shared pathogens across regions, underscores the importance of continual monitoring and surveillance. PCR panels offer valuable diagnostic insights, demanding careful interpretation based on clinical presentation, exposure and vaccination history, and disease patterns. Emphasizing vaccination at intake, timely quarantine, isolation and antibiotic treatment for bacterial cases, and proactive measures against overcapacity emerge as pivotal in managing and preventing CIRDC outbreaks. By refining protocols for disease prevention and population-level management, shelters can elevate the health and welfare for our canine companions, reducing reputational risk, as well as conserving shelter resources, increasing space and capacity for other animals in need.

References:

1. 1. University of Florida Shelter Medicine Program. (2023, November 27). Mysterious Respiratory Disease Spreading amongst Dogs across the Country. https://sheltermedicine.vetmed.ufl.edu/2023/11/27/mysterious-respiratory-disease/
2. Weese, S. (2024, Jan 10). Canine Respiratory Disease Outbreak Update: Jan 10, 2024. Worms and Germs Blog. https://www.wormsandgermsblog.com/2024/01/articles/animals/dogs/canine-respiratory-disease-outbreak-update-jan-10-2024/
3. Crawford, C., Karsten, C., Weese, S. (2023, December 11). Canine Respiratory Disease Complex (webinar). Maddie’s Pet Forum. https://forum.maddiesfund.org/discussion/community-conversations-121123-canine-infectious-respiratory-disease-complex
4. Edinboro, C. H., Ward, M. P., Glickman, L. T. (2004, February 26). A placebo-controlled trial of two intranasal vaccines to prevent tracheobronchitis (kennel cough) in dogs entering a humane shelter. Prev Vet Med, 62(2), 89-99. https://doi.org/10.1016/j.prevetmed.2003.10.001. Erratum in: Prev Vet Med. (2005, July 12). 69(3-4), 309-10.
5. Lappin, M., Weese, S., Journey, C. (2023, November 30). Separating Fact, Fiction, and Uncertainty: Canine Respiratory Illness Q&A with Trupanion. Webinar. https://k9illness.trupanion.com/
6. Merck Animal Health. (2023). Know the Spread: Canine Respiratory Infections in the US. https://www.dogflu.com/outbreak-map/
7. 6. Weese, S. (2023, October 12). Canine Influenza in Alberta. Worms and Germs Blog. https://www.wormsandgermsblog.com/2023/10/articles/animals/dogs/canine-influenza-in-alberta/
8. Weese, S. (2023, October 25). Update: Canine Influenza in Alberta. Worms and Germs Blog. https://www.wormsandgermsblog.com/2023/10/articles/animals/dogs/canine-influenza-update-alberta/
9. Miller, L., Janeczko, S., Hurley, K. F. (2021). Infectious Disease Management in Animal Shelters. United Kingdom: Wiley. Chapter 10: Canine Infectious Respiratory Disease, p. 221-255.
10. Crawford, C. (2021). Canine Respiratory Infections In Shelters. University of Florida Maddie’s Shelter Medicine Program, p. 1-5. https://sheltermedicine.vetmed.ufl.edu/wordpress/files/2021/05/Canine-Respiratory-Infections-in-Shelters.2021.pdf
11. Canadian Animal Health Surveillance System. (2022, April 6). Disease Alert: Canine distemper in British Columbia. https://cahss.ca/cahss-tools/disease-alerts/distemper-bc-220414
12. Canadian Animal Health Surveillance System. (2022, March 16). Disease Alert: Canine distemper in British Columbia. https://cahss.ca/cahss-tools/disease-alerts/canine-distemper-in-british-columbia-november-10-2021
13. Lappin, M. R., et al. (2017). “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.” Journal of Veterinary Internal Medicine, 31(2), 279-294
14. Shelter Animal Count. (2023, December 12). An estimated 245,000 additional dogs and cats are waiting in the shelter system this holiday season compared to last year.  https://www.shelteranimalscount.org/estimated-245000-additional-dogs-and-cats-in-the-shelter-system-this-holiday-season/
15. University of Florida Shelter Medicine Program. (2021, March 17). Giving Shelters a Break from Pneumovirus. https://sheltermedicine.vetmed.ufl.edu/2021/03/17/giving-animal-shelters-a-break-from-pneumovirus/
16. Weese JS, Anderson MEC, Berhane Y, Doyle KF, Leutenegger C, Chan R, Chiunti M, Marchildon K, Dumouchelle N, DeGelder T, Murison K, Filejksi C, Ojkic D. Emergence and Containment of Canine Influenza Virus A(H3N2), Ontario, Canada, 2017-2018. Emerg Infect Dis. 2019 Oct;25(10):1810-1816.
17. Weese, Scott. “Let Doxycycline Off the Leash… No Need to Avoid It in Young Growing Animals.” Worms and Germs Blog, 15 January 2024, https://www.wormsandgermsblog.com/

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