A potentially fatal mystery illness in dogs is spreading in the US. It starts with a cough

A mysterious and potentially fatal respiratory illness in dogs has been reported in several states across the country, as veterinarians continue to search for what may be causing the condition that has killed some dogs.

The illness starts out as a cough that can last for several weeks, but it may not respond to antibiotics, which can leave the dog struggling to breathe and with severe pneumonia.

"It seems to happen very, very quickly — to go from this cough that’s just won’t go away ... and then all of a sudden they develop this pneumonia," Dr. Lindsey Ganzer, veterinarian and CEO at North Springs Veterinary Referral Center in Colorado Springs, Colorado, tells TODAY.com.

Ganzer estimates her hospital has seen close to 30 dogs with the condition since the middle of October. She adds that cases are "really not slowing down," with two to three coming in a day, most requiring hospitalization. She says four to five of the dogs her hospital has seen have died due to the illness, but they arrived already in respiratory distress with pneumonia.

It's not a time for dog owners to "become paralyzed with fear," Dr. Kurt Williams, director of Oregon Veterinary Diagnostics Lab, who's been researching the illness for the past month and a half, tells TODAY.com.

"I think concern is fine," he says, adding that dog owners may want to consider taking precautions to prevent illness, such as avoiding scenarios with other dogs and making sure dogs are up to date on vaccinations, especially against respiratory diseases.

Mystery dog illness 2023

Dogs with this mystery illness usually have coughing, sneezing, eye or nose discharge, are abnormally tired, and do not test positive for any of the common causes of respiratory illness, the Oregon Department of Agriculture noted in a Nov. 9 press release.

Dogs are most likely to contract the infection by being in close contact with numerous other dogs — so places like day care, dog parks, groomers or boarding kennels, Ganzer explains.

Since mid-August, the Oregon Department of Agriculture has received reports of over 200 cases of the illness from veterinarians in the state. It's not known how many dogs have died.

A spokesperson tells TODAY.com that cases are still being reported in Oregon and that the department is working with other health authorities to try to find the cause of the illnesses. Veterinarians who see cases are encouraged to report them to the Oregon Department of Agriculture.

Williams points out that one of the challenges is defining what cases "fall under this umbrella of this particular entity that we're all investigating." That's because dogs can develop a cough for a variety of reasons, and it takes time to rule out known causes.

"We're still trying to pin down a potential cause or causes for the entity. At least in Oregon, it's given us some some challenges," Williams says, adding that he was contacted late Wednesday about running tests on a dog that died from severe respiratory disease.

Williams speculates the cause could be a virus because "the way the cases are presenting, the way that they're apparently spreading, anecdotally, of course ... it sounds infectious." But he says it's important for researchers to "keep an open mind" to other causes.

In its press release, the Oregon Department of Agriculture noted that the illness can progress in three ways: a mild to moderate cough for six to eight weeks or longer that either doesn't respond to antibiotics or only responds a little; chronic pneumonia that doesn't respond to antibiotics; or severe pneumonia that "often leads to poor outcomes in as little as 24 to 36 hours."

While this mystery dog illness is making headlines in 2023, Ganzer notes that it's been around since last year. Her hospital has been sending off samples from the dogs to a research lab in New Hampshire, which has been studying the illness since 2022.

Where in the U.S. has the illness been reported?

According to Ganzer and the Oregon Department of Health, cases that match the description of the mystery dog illness have been reported, officially or anecdotally, in:

• Oregon
• Colorado
• New Hampshire and the surrounding Northeast area
• California
• Indiana
• Illinois
• Washington
• Idaho
• Georgia
• Florida

The American Veterinary Medical Association tells TODAY.com in a statement that it's monitoring cases of canine respiratory illness in Oregon and has been in contact with state officials. The Association reiterates that the cause of the illness is still unknown.

In recent weeks, there have also been multiple reports of outbreaks of a deadly respiratory illness in dogs at animal shelters in the U.S. The San Diego Humane Society has lost four dogs to a "severe respiratory canine illness," according to a Nov. 15 press release.

However, the disease at San Diego Humane Society has been linked to two particular bacteria, Strep zoo and Mycoplasma. Dr. Zarah Hedge, chief medical officer at San Diego Humane Society, tells TODAY.com that she believes the outbreak at her shelter and others she's heard about — such as one in Las Vegas — are not related to the mystery dog illness. That's because Strep zoo and Mycoplasma are easily treatable with the right antibiotics, which saved many dogs at her shelter during the recent outbreak. Also, the sick dogs she's seen didn't have a long-term cough, she says.

The American Veterinary Medical Association also tells TODAY.com there's no indication of a connection between the outbreaks.

That said, Hedge is still concerned about the damage that severe respiratory infections, both known and unknown, can cause in dogs, especially in shelters.

"We are seeing numbers of dogs coming into shelters that we haven't seen in a very long time," Hedge says. "A lot of shelters across the country are overcrowded, and it just sets you up for disease outbreaks."

Symptoms of the mystery dog illness

Symptoms of the mystery dog illness include:

• Coughing that doesn't get better on its own after a week or so
• Sneezing
• Nasal or eye discharge
• Lethargy
• Trouble breathing, especially from the stomach
• Blue or purple gums (due to not getting enough oxygen)

Ganzer stresses that any dog owners who notice their dog coughing, especially if they recently spent time with lots of other dogs, such as at a day care, kennel or dog park, should be taken to the vet right away. You shouldn't wait to see if the cough clears up on its own as earlier treatment makes a big difference in recovery, she adds.

What owners can do about the mystery dog illness

Ganzer says her No. 1 tip is to keep dogs from areas where they're likely to come into contact with other dogs (but do not delay taking your dog to the vet for needed medical care).

Keeping dogs out of these situations may be difficult for many families as the holidays approach because many people rely on boarding kennels when they travel. However, Ganzer says to avoid boarding dogs over the holidays "if at all possible," adding that she's "so scared" about what may happen with the mystery illness after dogs across the country are boarded for the holidays.

"I understand that there are circumstances that are unavoidable and that some people have to (board their dogs), but I would not take this lightly," she explains. "If there's somebody that can even just come to your house and let your dog out, that's a better option."

Williams agrees that it’s “prudent” to be concerned right now about putting dogs in scenarios where they may come into contact with many other dogs. If you need to put your dog in such a situation, he suggests contacting your vet ahead of time for guidance.

To keep your dog safe and healthy overall, Hedge also recommends making sure your dog is up to date on routine vaccinations.

If your dog has been diagnosed with the mystery coughing illness, Ganzer suggests asking your veterinarian about submitting a sample to a research lab to help with the efforts to identify the cause.

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