A mysterious respiratory illness is spreading among dogs and baffling veterinarians. Here’s what owners can do

From New Hampshire to Oregon, researchers are trying to figure out what’s causing an infectious respiratory disease among dogs that has turned deadly in rare cases.

The mysterious illness is described as an “atypical canine infectious respiratory disease,” the Oregon Department of Agriculture said in a November 9 news release. Symptoms include coughing, sneezing, eye or nose discharge and lethargy.

Veterinarians in Oregon have reported more than 200 cases of the disease since mid-August. Other cases have been reported in Colorado, Illinois and New Hampshire.

“Based on the epidemiology of the cases reported at this point, the cases appear to share a viral etiology, but common respiratory diagnostic testing has been largely negative,” Oregon State Veterinarian Dr. Ryan Scholz told the American Veterinary Medical Association.

In other words, dogs with the unidentified illness show similar signs of an upper respiratory disease but generally don’t test positive for common respiratory diseases. And the disease is generally resistant to standard treatments, said Dr. David B. Needle, a pathologist at the New Hampshire Veterinary Diagnostic Laboratory and clinical associate professor at the University of New Hampshire.

“Fatalities do not seem to be a large part of the syndrome we are investigating, with rare animals developing an acute and sometimes fatal pneumonia after the longer chronic disease,” Needle said. “We think these may represent secondary infections.”

Where did the disease come from?

Needle said he’s part of a team trying to identify the disease and find common DNA segments by collecting samples from local veterinary clinics and comparing the results.

“If what we have identified is a pathogen, it is likely that the bacteria is host-adapted bacteria with long histories of colonizing dogs,” Needle said. An “evolutionary event” like spontaneous mutation or getting a gene from a different source could then have led the bacteria to become virulent, he said.

He said researchers have received samples from Oregon and expect to receive samples from Colorado, Illinois and other states for testing.

The Washington Animal Disease Diagnostic Laboratory has also reported cases of a mysterious canine disease, the lab’s director told CNN in an email.

“There has been an uptick in the numbers of dogs with respiratory disease, (coughing, lethargy, fever) and the signs have been persisting longer than a few days,” said Kevin Snekvik, the laboratory’s executive director and a professor at the Washington State University College of Veterinary Medicine.

Snekvik said his Washington lab has not reported any canine deaths from the mystifying disease, but said labs in other states have reported a few deaths.

What can dog owners do?

While the news may be concerning, “We suggest caution rather than worry,” the Oregon Veterinary Medical Association’s website says.

While this particular disease is unusual, “Periodic outbreaks of Canine Infectious Respiratory Disease Complex (CIRDC) can occur in a dog population. At least nine different bacteria and viruses have been linked as causes of CIRDC, which is transmitted by respiratory droplets,” the association said.

“Infection with more than one bacterial or viral agent is common. Symptoms include coughing, sneezing, nasal and/or eye discharge, and lethargy. If your dog shows these symptoms, please contact your veterinarian.”

Dog owners should help keep their pets healthy by making sure they’re up-to-date on all vaccines, such as those for canine influenza, Bordetella and parainfluenza, the association said. Other tips include:

• Reducing contact with large numbers of unknown dogs. Just like with other respiratory pathogens, the more contacts your dog has, the greater the risk of encountering a dog that’s infectious.
• Reducing contact with sick dogs. This can be harder to determine but if a dog looks sick (coughing, runny nose, runny eyes), keep your dog away from it.
• Keep sick dogs at home and seek veterinary care.
• Avoid communal water bowls shared by multiple dogs.

For more CNN news and newsletters create an account at CNN.com