Veterinarians and animal shelters around the country continue to report cases of a highly contagious, sometimes fatal, mystery dog illness. Still, the disease that swept the United States last fall has experts somewhat stumped. Researchers searched for answers using samples from infected dogs while vets warned pet owners in the hopes of further preventing the spread of the virus.
Severe, fast-moving, and highly contagious
It begins with a cough. A normal case of canine infectious respiratory disease complex (CIRDC), more commonly known as kennel cough, presents with the same symptoms as this mysterious illness. Symptoms include coughing, loss of appetite, runny nose, lethargy, and sometimes a low fever. However, this new illness might last for weeks, unlike kennel cough, which usually clears up in seven to 10 days. It can even lead to fatal instances of pneumonia.
With the severity of symptoms and resistance to treatment, some veterinarians initially believed the illness was a new virus infecting younger canines and causing lengthier illnesses. Moreover, the usual treatment for pneumonia in dogs may not be enough for this severe, fast-moving disease.
“I would say [there’s been] maybe a 50% increase in the number of coughing dogs we detect,” Dr. Amanda Cavanagh of Colorado State University Veterinary Teaching Hospital told Scripps News Denver. “And many of those dogs are actually passing away or being euthanized because of this really severe, fast-moving, really intense pneumonia,” she added.
Cavanagh also stated that social environments, such as boarding facilities and dog parks, are particularly susceptible. Animal shelters struggled to combat the spread of the contagious mystery illness killing dogs. This is particularly true among those already experiencing capacity crises from an influx of pet surrenders.
Uncertainty over whether novel virus is being misdiagnosed
In North Carolina, the Wake County Animal Shelter closed in early October due to a quickly-spreading, severe illness. According to WRAL News, the closure was expected to be temporary. The shelter reported the illness as Canine Influenza. Despite this, the infected dogs exhibited symptoms similar to the mystery illness killing dogs across the country, including cough, nasal discharge, and cases resulting in severe pneumonia. The shelter serves the state’s capital county, which is home to more than a million people. In the time since, four dogs died from the rapidly spreading disease. More have been sick and recovered.
Nearly two months later, the facility announced its move to re-open as it finally saw a decrease in illness symptoms. Unfortunately, the extended closure resulted in some people abandoning and dumping animals outside the facility, as per CBS-17. Local groups, like Neshama Animal Rescue, stepped up efforts to find fosters and adoptive pet parents in the meantime.
As of Thanksgiving day in 2023, a veterinarian in Cary reported at least three cases of the mystery illness killing dogs, according to WRAL.
Rise in cases of mystery dog illness
In other states, experts reported a concerning number of cases. According to ABC 10 News, veterinarians across Oregon documented at least 200 reports of the mystery illness to the State Department of Agriculture. The data mentions the deaths of multiple dogs.
As per the reporting by The Hill, experts categorize cases into three groups. The first is persistent tracheobronchitis, lasting at least six weeks and resistant to conventional antibiotic treatment. Second is persistent pneumonia, in which affected dogs exhibit a poor response to antibiotics. Finally, the third type is characterized by rapid-onset acute pneumonia, capable of significantly impacting canines within a mere 24-hour timeframe.
Kurt Williams is the director of the Oregon Veterinary Diagnostic Laboratory. Williams stated, “We’ve been undertaking a series of tests mostly looking for common sorts of expected bacterial and viral pathogens.” He went on to share, “we’re also doing some testing for perhaps novel agents as well — novel viruses in particular.”
Andrea Cantu-Schomus, a department spokesperson for the Department of Agriculture, released an emailed statement to Oregon Public Broadcasting (OPB). She shared, “Unfortunately, very few of those dogs have received a full necropsy to determine the cause of death.”
The agency collaborated with pathologists and virologists from state and federal veterinary facilities. Additionally, they’re working with the Oregon Veterinary Diagnostic Laboratory at Oregon State University. Together, the partnering groups hope to determine what is causing the illness.
Researchers began investigating virus a year ago
Not all scientists were shocked by the spread of the mystery illness. Some were researching the unknown virus long before it began making headlines across the country.
David Needle is a senior veterinary pathologist at the University of New Hampshire’s Veterinary Diagnostic Laboratory. For nearly a year, he dedicated his efforts to unraveling the cause of the disease.
Working alongside colleagues from the university’s Hubbard Center for Genome Research, Needle’s laboratory researched viral samples from dogs in Rhode Island, New Hampshire, and Massachusetts. Additional samples arrived from other states, including Oregon and Colorado.
Varying infectious outbreaks cause confusion
At the San Diego Humane Society, veterinary professionals identified two pathogens responsible for an infectious outbreak amongst the dogs leading to a temporary pause in intake last fall, as per reporting by NBC-7. Veterinarians, however, could identify and treat pathogens. This confirmed the illness was not the same as the mystery virus spreading across the nation.
Mycoplasma — a bacterial infection — and Streptococcus Equi subspecies zooepidemicus — also referred to as Strep Zoo — may have been working together. Researchers believe the pathogen combination exacerbated the effect of the infection, making the illness more difficult to treat. The one-two pathogen punch, however, was not linked to the unidentified mystery respiratory illness.
At the time of the outbreak, the shelter exceeded dog housing capacity by 178%. According to reporting from the American Veterinary Medical Association, Dr. Laura Bunke, San Diego Humane Society’s John R. Peterson Foundation shelter medicine resident, said overcrowded conditions make the dogs more vulnerable to Canine Infectious Respiratory Disease Complex (CIRDC). The conditions heighten the dogs’ stress levels and hamper the staff’s ability to sanitize and disinfect the facilities effectively.
It is possible that the media attention on the Strep Zoo outbreak coincided with the timing of reports of the mystery illness, causing some confusion.
According to the American Veterinary Medical Association (AVMA), “there are no indications of a connection between these CIRDC cases and an outbreak of Streptococcus equi subsp. zooepidemicus at the San Diego Humane Society, which resulted in four dogs being euthanized.” Fortunately, no new cases of Strep Zoo have been reported.
Poor clinical understanding of mystery illness
Without a comprehensive system to track dog illnesses in the U.S., it’s hard to know if individual cases and fragmented reports point to a bigger problem.
“It’s entirely possible that there are just a ton of different bugs and viruses causing disease in different parts of the country,” Dr. Jane Sykes, a professor at UC Davis School of Veterinary Medicine, told NPR. “We just have to be a bit careful about panicking.”
Dr. Scott Weese, an infectious disease veterinarian at the Ontario Veterinary College, pointed out that the increasing amount of data may be getting mixed up. “Do we have more disease? And do we have something new? Because those are not necessarily connected,” Weese explained.
Weese further acknowledges that specific regions in the country are witnessing an increase in cases of canine respiratory illness. Nevertheless, it’s possible that extensive media coverage contributed to the perception of a nationwide outbreak that might not accurately reflect the actual situation. “I get an email a couple of times a week saying, ‘hey, are we seeing more respiratory disease in dogs?” Weese says, “But I’ve been getting that email for like five years.”
Although there is a poor clinical understanding of this respiratory illness, many thought it was still possible that a new pathogen was spreading.
More recently, however, the U.S. Department of Agriculture’s National Veterinary Services Laboratories began sequencing some cases. In a statement made to USA Today in Feb. 2024, researchers discovered many had a common cause that was not linked to a single infection or a new pathogen.
Possible pathogens identified
While clinical signs present similar to kennel cough, the disease does not test positive for pathogens relating to the illness or similar respiratory infections. According to a Nov. 21 report from the University of New Hampshire’s Veterinary Diagnostic Laboratory, the illness “[seems] to be refractory to standard medical treatment and are usually negative on syndromic canine respiratory disease PCR testing.”
“We found no known DNA or RNA viruses, no bacterial pathogens, no fungal pathogens,” Needle told NPR. “We were sort of at a breaking point.”
Finally, a breakthrough emerged: a brief segment of DNA that, based on Needle’s assessment, seems to belong to a previously unique bacteria.
“We think this may be a pathogen,” he shared. Continuing, he added, “It’s something novel. It’s in a proportion of the cases. It’s funky.” Interestingly, the report also stated that certain breeds were not at a higher risk of contracting the illness. Despite this, brachycephalic dog breeds, such as Pug, Pekingese, and Bulldog breeds face an elevated risk for the severity of respiratory illnesses.
In an updated report from Jan. 25, 2024, The Hubbard Center for Genome Studies (HCGS) and the New Hampshire Veterinary Diagnostic Laboratory (NHVDL) at UNH uncovered further preliminary findings in their diagnostic inquiry. Through screening using 16s rRNA gene metabarcoding, they discovered additional evidence of a potential novel bacterial respiratory pathogen. The finding is consistent with their initial observations in samples collected from dogs across multiple states. Specifically, among 226 tested dogs, genetic material from this potential pathogen was detected in 31 cases. The findings indicated a noteworthy presence warranting further investigation.
In the meantime, Needle told USA Today, “People gotta chill out.”
Warning for dog owners
Despite the widespread circulation of reports, there’s nothing at this point “that would indicate there’s a national outbreak, anything that would indicate these are all medically connected to each other,” says Dr. Silene St. Bernard, the regional medical director for VCA Animal Hospitals. Still, some experts desperately hope to bring attention to dog owners.
Veterinarians like Dr. Cavanagh urge pet owners to bring any dogs showing signs of consistent coughing to a vet. “We can ultrasound the lungs to see if there is a problem that is related to pneumonia or contagious pneumonia that seems to be going around,” Cavanagh shared with ABC-30.
Symptoms of mysterious illness to watch for in dogs
Kiro 7 News reported receiving similar advice from other veterinary professionals. Kevin Snekvik, the Executive Director of the Washington Animal Disease Diagnostic Lab at Washington State University, warned pet owners to pay close attention to their dogs and note any symptoms of the illness.
“Your dog will run a fever and they won’t feel good,” Snekvik began. Continuing, he added, “they’ll become lethargic” and “want to lie around more when normally they’d be wanting to play outside.” Snekvik also cautioned pet owners to pay attention to “the coughing part of it.” Emphatically, he suggested that the red flags to watch out for are a cough that “becomes more productive” and “more of a wet cough, like a hacking cough.”
Because of the infection’s severity, it’s critical to keep an eye out for symptoms in your dogs. Consistent coughing, changes in appetite, and variances in energy levels are all warning indicators, according to veterinarians.
In reporting from the Associated Press, Kurt Williams emphasized that pet owners should not panic. Instead, he recommends ensuring that pets are up-to-date on vaccinations, specifically those providing protection against various respiratory illnesses. Veterinary professionals also advise pet owners to refrain from taking their pets to dog parks and other social settings until the number of cases diminishes.
Pet owners isolated pets during outbreak
As reports of cases increased, many dog owners chose to isolate their pets.
Katie Wolhowe, a resident of Minnesota, is a pet parent to a two-year-old German Shepherd and Rottweiler mix named Venus. She informed Newsweek that she and her husband chose to keep Venus away from dog parks temporarily to prevent any potential illness during the height of the mysterious dog virus outbreak.
“She is our furry family member and like a child to us, and we don’t want any harm done to her. We also want to reduce further spread of the virus,” Wolhowe explained.
Jules Dahbura, a pet owner from New York City, likewise kept her two dogs, Benny and Remy, away from other people following a close call with the respiratory illness. Remy, an 11-year-old Boxer mix, spiraled into critical condition with acute pneumonia and a high temperature. Benny, Dahbura’s other dog, showed very brief symptoms.
In fact, Remy’s sickness was so serious he could no longer walk and was on the verge of death. Even though emergency veterinary care eventually allowed him to recover completely, the underlying reason for his condition remained unknown. Still, Remy presented with similar symptoms to the mystery illness.
Overwhelmed by the uncertainty, Dahbura and her family made the difficult decision to stop taking Remy to dog parks. She chose to protect Remy, even at the expense of normalcy for Benny.
Uncertainty remains as cases wane
After a fearful period in which pet owners isolated their pets or desperately sought treatment for the mystery virus, experts believe cases are decreasing. That said, the mysterious dog illness does still exist.
“While the lack of a central data collection agency makes tracking cases difficult, experts believe that cases have waned,” USA Today reported. This illness may be part of a growing trend of canine respiratory sickness that evolved in the previous few years. Despite the severity, it’s possible this mystery illness was just another round of seasonal ups and downs for common dog illnesses.
“If we get a new pathogen…it’s pretty dramatic,” emerging animal disease expert Dr. Scott Weese stated. He further explained this illness did not erupt dramatically like COVID-19. “We’ve had this gradual increase in respiratory disease. We get these blips that occur and the blips get more obvious when you’ve already got a higher baseline level of disease.”
The precise cause of the recent rise in instances is unknown. However, experts surmise that a larger dog population, less immunity to illnesses, and increased exposure are the main culprits. Contributing causes, according to Weese, include dogs returning to shared care facilities, the popularity of flat-faced dog breeds, and disrupted vaccination schedules during the pandemic.
Precautionary measures from experts
Experts confirmed cases of the illness in multiple states, including California, Colorado, Oregon, New Hampshire, North Carolina, Rhode Island, Massachusetts, Florida, Idaho, Indiana, Illinois, and Georgia. Last December, ABC News also shared confirmed cases in Nevada and Pennsylvania. In total, at least 16 states reported cases of the illness.
Although cases are decreasing, the risk of infection remains present. As reported by Newsweek, Dr. Athena Gaffud from Veterinarians.org offered suggestions to aid pets in a time that has both veterinary experts and pet parents concerned. According to Gaffud, the well-being of pets extends beyond isolation.
“Pet owners can keep their pets safe by making sure their pets are vaccinated against common infectious diseases in the area,” Gaffud advised. “Keeping their immune system strong with proper nutrition and supplements would also help to ward off infections.”
Furthermore, Gaffud advised pet parents to keep their dogs indoors if there is a reported flu or other canine epidemic in nearby areas. As spring break and subsequent travel approaches, it is important to consider the risk boarding facilities may present.
