A mysterious respiratory illness is spreading among dogs across the U.S., sending veterinarians and health officials scrambling to understand the disease and contain its spread. As of early December, cases have been reported in over a dozen states. While the illness does not seem to pose a threat to human health, it has caused severe and even fatal sickness in affected dogs.
Illness Manifests as Coughing, Fatigue and Eye Discharge
The first cases of the respiratory illness were spotted in Michigan in August 2022. Since then, the disease has spread to over a dozen states including California, Illinois, Massachusetts and Pennsylvania.^1
The most common symptoms appear to be coughing, fever, fatigue/lethargy, loss of appetite, and eye discharge. Some dogs have also experienced vomiting or diarrhea. While most dogs recover, veterinarians have reported fatalities from the disease.^2
The illness seems to manifest first as a cough that persists and worsens over days or weeks. Affected dogs often develop eye discharge and become increasingly lethargic. More severely affected dogs have developed high fevers and labored breathing.
While any breed or age of dog seems susceptible, veterinarians have noted increased illness severity among younger dogs and brachycephalic (short-nosed) breeds.^3
Transmission Mechanism Remains Unclear
The underlying cause and transmission mechanism behind the respiratory illness remain unclear. Veterinarians suspect the disease stems from a virus or bacterium that passes between dogs.
Given the similarity to kennel cough, many vets initially believed the disease was a novel strain of kennel cough (also known as canine infectious respiratory disease complex or CIRDC). Kennel cough is an upper respiratory infection caused by Bordetella bronchiseptica and canine parainfluenza virus that leads to hacking coughs.^4
However, testing has yet to identify Bordetella, parainfluenza or other known pathogens like canine influenza as the definitive cause. Several vets report successfully treating cases with medications like antibiotics, steroids and bronchodilators.^5 This suggests the illness may stem from bacterial or viral co-infections rather than a single novel agent. Nonetheless, an unknown respiratory pathogen driving the outbreak remains a possibility.
Transmission likely occurs through saliva, respiratory droplets or fomites (contaminated objects or surfaces). Boarding/daycare facilities and dog parks could facilitate spread through shared spaces, toys and bowls. However, many affected dogs have no known interaction with other dogs, suggesting additional transmission modes like human handling.^6
Investigation Underway to Pinpoint Cause and Contain Spread
With cases accumulating, veterinary health officials have launched investigations to understand the root cause and contain the respiratory illness. Cornell University’s veterinary college is leading genomic analysis to pinpoint whether a novel pathogen or other factor drives the outbreak.^7
Several academic labs are also pursuing culturing, microbiome and immunoassay testing on samples from affected dogs. By identifying the responsible agent, researchers hope to develop targeted diagnostics and treatments.^8
State veterinary officials are spearheading epidemiologic tracking of cases to elucidate transmission factors. The CDC and USDA are also monitoring the outbreak, though emphasize the illness does not seem to pose any human health hazards currently.^9
In the meantime, veterinarians advise closely monitoring dogs for respiratory illness symptoms. They encourage proper hand hygiene when contacting dogs to limit potential human-driven transmission.^10
Boarding Facilities and Dog Parks Take Added Precautions
The uncertain transmission mechanisms have prompted precautionary measures at boarding facilities, doggie daycares and dog parks where respiratory spread could occur more easily.
Many facilities have temporarily closed off areas for group play. Staff are stepping up cleaning/disinfection of common areas and monitoring dogs closely for any coughing. Some facilities are requiring updated vaccine and health certificates.^11
A number of dog parks have similarly closed as a precautionary measure given the communal nature of these spaces. Owners across the country report curtailing visits to dog parks and play dates with other pups.^12
Vets Caution Against Panic as Investigations Continue
While concerning and disruptive, veterinarians caution dog owners against panic regarding the respiratory illness. They emphasize that most infected dogs recover with proper supportive care.^13
Health officials also stress that despite circulating rumors, there is no evidence currently that the sickness stems from any contaminants or toxins. As scientists work rapidly to pinpoint the root cause, owners should remain vigilant but not overreact.^14
The investigation and precautionary measures will likely continue for weeks until researchers can provide definitive answers on the disease. In the meantime, veterinarians advise keeping dogs up-to-date on core vaccines like parvo, rabies and DA2PP (distemper/adenovirus/parainfluenza/parvovirus) as an illness prevention measure. They also suggest avoiding dog parks and closely monitoring respiratory health.^15
This respiratory outbreak marks the latest in a series of new illnesses to arise among domestic dogs, from canine influenza to leptospirosis to staph. With over 90 million pet dogs across the U.S., scientists stress the need for continued vigilance and research into emerging zoonotic and veterinary diseases. While this respiratory illness does not appear to pose risks for human infection, tracking and containing such outbreaks remains crucial for ensuring animal and public health.
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