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Rocky Mountain Spotted Fever Cases Are on the Rise

Yikes! A new strain of tick-borne disease Rickettsia could infect pets and their people.

by Alycia Washington, DVM
June 17, 2022
A woman lovingly petting a dog.
Alba Vitta / Stocksy

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Ask anyone to name an animal that contributes literally nothing beneficial to the planet, and mosquitoes and ticks will easily be top contenders. Their uselessness is especially obvious when it comes to dogs. Mosquitoes are responsible for infecting tens of thousands of dogs with heartworm disease every year (seriously folks, keep your pups on monthly heartworm preventatives), while ticks are responsible for infecting dogs with conditions like Lyme disease, Ehrlichiosis, and Rocky Mountain Spotted Fever — a disease caused by the bacteria Rickettsia rickettsii, a new strain of which is currently on the rise in the U.S.

Rickett...what?

Rickettsia rickettsiia is a bacteria transmitted by ticks that can infect the cells lining a dog’s blood vessels. There are multiple spotted fevers caused by Rickettsia across the world that affect both dogs and people. In North America, Rickettsia rickettsii, or Rocky Mountain Spotted Fever, is the only spotted fever disease that causes issues in dogs. Not all dogs infected with these bacteria show symptoms, but the ones that do can develop fever, muscle pain, lameness, skin lesions, eye problems, or neurological abnormalities. Rocky Mountain Spotted Fever can be diagnosed with blood tests, and it can be effectively treated with antibiotics and supportive care when caught early.

So, what’s up with this new strain of Rickettsia?

All this information is based on data from three cases in the southern region of the United States. In 2018, a 10-year-old mixed breed dog in Tennessee was seen by his veterinarian for fever, lethargy, and poor appetite. Blood work, including a tick panel, revealed that he was positive for R. rickettsii. In 2019, a nine-year-old Boston Terrier was taken to his vet for fever, lethargy, trouble walking, and painful elbows. This dog had recently visited an area in Arkansas where ticks are widespread. His tick panel was also positive for R. rickettsii.

Lastly, later in 2019, a nine-year-old Terrier in Oklahoma was evaluated for fever, lethargy, increased urination, and a tender abdomen. Guess what his tick testing showed? Yep, positive for R. rickettsii. All these dogs were treated for Rocky Mountain Spotted Fever. The first two dogs recovered well. Unfortunately, the third dog developed some pretty serious complications and was eventually euthanized. It is suspected that that this dog’s pre-existing health issues complicated his recovery. All three cases had blood samples submitted to a laboratory to confirm the diagnosis.

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This is where the researchers enter the picture. The smarty pants at North Carolina State University obtained samples from a large number of dogs and used a process called PCR (which stands for polymerase chain reaction) to make copies of the DNA sequences commonly found in bacteria carried by ticks. When they did this, they found a match between the three dogs’ samples, but only a 95 percent match with Rocky Mountain Spotted Fever.

With further testing, they also found a close relationship with R. heilongjiangensis and R. massilae, two spotted fever diseases that affect humans. They concluded that this new species of Rickettsia could possibly infect both dogs and humans. Since standard testing in dogs generates positive results for R. rickettsia, it is possible that this species is more widespread than we know. All this information is still pretty new (the bacteria doesn’t even have a name yet), but researchers are digging deeper to learn as much as they can.

What can you do to protect yourself and your pup?

Avoid wooded and brushy areas (where gross ticks like to hang out), use tick-repellent and tuck your pants into your socks when hiking, and make sure your dog is on safe, effective tick prevention every month.

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alycia washington, dvm

Alycia Washington, DVM

Alycia Washington, DVM, is a small animal emergency veterinarian based in North Carolina. She works as a relief veterinarian and provides services to numerous emergency and specialty hospitals. Dr. Washington is also a children’s book author and freelance writer with a focus on veterinary medicine. She has a special fondness for turtles, honey bees, and penguins — none of which she treats. In her free time, Dr. Washington enjoys travel, good food, and good enough coffee.