The Dangers of Rocky Mountain Spotted Fever for Dogs

Many thanks to jarah’s mom for researching RMSF and answering my questions and generally getting me out of a confused state. Thanks also to Lori S. and Judith B. for their support and info, and to the many other helpful friends and well-wishers.  

On November 6, 2014 my dear dog Clara got a blood work result that very strongly indicated that she had Rocky Mountain Spotted Fever, a serious, potentially fatal tick-borne disease that affects people, dogs and some other animals in North, Central, and South America. Clara had been showing symptoms for quite some time.

Clara is probably not in danger for her life at this point, and most people wouldn’t even be able to tell that she is sick. Although she is on a strong course of antibiotics, some effects of the infection remain. Time will tell whether she will recover completely. I’m sharing the story of her diagnosis in case it will help others. This disease can be difficult to diagnose, and a timely diagnosis can save a life in some cases.

A tan dog with a black muzzle and tail is on a chaise longue. It's sunny and she is looking straight into the camera
Clara catching some rays. She looks serious but is wagging her tail.

Diagnosis

In September 2014, I started to notice that Clara was getting increasingly stiff and weak in her hind end. This worsened, and by early November when she was finally diagnosed, she had also gotten prone to trembling, not only when she was cold or excited, but sometimes for no apparent reason, even while asleep.

Thinking back, for as long as several months before this, she had run and jumped less when playing with Zani and had less stamina for playing ball. I didn’t mention it in the post, but you can see in the video in “How My Dogs Play” that Clara typically waits in the corner while Zani runs around the yard (previously, she would have run after her every time). Clara also lies down a lot in the play session, which is very polite and self-handicapping of her, but also could have been because she was tired.

She also had a rash on her chest, abdomen and legs in October 2014, which may or may not have been connected.

I made the movie below to chronicle her symptoms, but held back for some time on publishing it. I wanted to be as sure as possible that her diagnosis was correct and that there wasn’t an additional problem or other reason for her symptoms.

The symptoms of tick-borne diseases vary greatly and also can be confused with many other diseases and conditions. (There are quite a few of these diseases, the most well known of which is probably Lyme disease. I included some links in the Resources section at the bottom of this post that list all the types, for humans and dogs.)

So before the blood work to test for tick-borne and parasitic diseases was done, the following tests were performed:

  • extensive range of motion testing on hips and back legs (excellent!)
  • hip, pelvis, and back leg X-rays (clear!)
  • complete blood count including to test for muscle enzymes related to soft tissue damage. The muscle enzymes were fine, but the CBC showed a lowered platelet count, which is a typical symptom of tick-borne diseases.

The lack of other diagnoses plus the low platelet count made tick-borne diseases the next most likely candidate for Clara’s symptoms. She was put on antibiotics and more blood was drawn so she could be tested for tick-borne and parasitic diseases.

The subsequent blood work returned a Rocky Mountain Spotted Fever titer of greater than or equal to 1:1024, the highest result possible at that lab.  This high reading indicated that Clara had a large number of antibodies to the Rickettsia rickettsii bacteria and had been fighting the Rocky Mountain Spotted Fever infection for a while, probably weeks or months.

This movie is a bit hard to watch.

Link to the video for email subscribers.

Mechanism of the Disease

The Rickettsia rickettsii bacteria are introduced into the dog or other animal from the bite of a tick that has been attached for 5-20 hours.1)Comer, K. M. “Rocky Mountain spotted fever.” The Veterinary clinics of North America. Small animal practice 21.1 (1991): 27-44. (This is a very good reason to perform daily tick checks if your dog has been in areas where ticks are present.) The bacteria have been found to be transmitted by at least four tick species, but the most common are the American dog tick (what probably bit Clara) and the Rocky Mountain wood tick.

Tick hemolymph cells infected with Rickettsia rickettsii
Tick hemolymph cells infected with Rickettsia rickettsii. Public domain image from the US Centers for Disease Control.

The bacteria are nasty. They immediately spread throughout the body via the blood and lymphatic systems and invade the cells of the endothelium, the cells in the lining of the blood and lymphatic vessels. They multiply there and move into the smooth muscle tissue. 2)Harrus, S., et al. “Rickettsiales.” Pathogenesis of Bacterial Infections in Animals, Third Edition (2004): 425-444. Since this is happening all over the body, the presenting symptoms can vary. Many different organs can be damaged or fail. The dog often bleeds from the nose or other locations.  There are joint and muscle problems. There can be gangrene in the extremities as the tissue dies. Dogs can have inflammation of the eyes, shortness of breath if the lungs are affected, have seizures or other nervous system symptoms, or can die suddenly of a heart attack. The kidneys can fail.

It most often affects dogs under four years old (Clara is 3 1/2). The response can range from no apparent problems at all, where the dog is infected but remains asymptomatic and lives a normal life, to death in a matter of days.

One dog study reported a mortality rate of 4%3)Comer, K. M. “Rocky Mountain spotted fever.” The Veterinary clinics of North America. Small animal practice 21.1 (1991): 27-44., but there doesn’t seem to be much information in general on that topic. The rate is probably higher. In studies where dogs were injected with large quantity of the bacteria (sorry to even mention this), mortality was 100% when the disease was untreated.4)Keenan, K. P., et al. “Studies on the pathogenesis of Rickettsia rickettsii in the dog: clinical and clinicopathologic changes of experimental infection.” American journal of veterinary research 38.6 (1977): 851-856.  In humans, RMSF is fatal in 20-25% of untreated cases and for 5-10% of treated ones.5)Bakken, Johan S., et al. “Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis—United States.” MMWR Morb Mortal Wkly Rep 55 (2006): 1.

Treatment

Clara is now on her second three-week round of Doxycycline, which luckily does not appear to upset her stomach. She obviously felt better in a metabolic sense after two days on the antibiotic; she was perkier and had more energy, and has stayed that way. But the stiffness has been much slower to change. I’ve been keeping a video record and I think she is finally improving, though. I have to remind myself that progress won’t necessarily be linear.

The Future

I feel a little weird for publishing this movie and blog, like I’m exaggerating the seriousness of Clara’s illness. But I’m not. Although the trembling has lessened, she still has periods of weakness and/or stiffness and is clearly fatigued after she exerts herself. I’m still trying to get my head around it all. I go from thinking she will be tragically affected for the rest of her life, to thinking there isn’t much to it and I’m overreacting. There’s still a flavor of “this can’t be happening…” But I’m also counting our blessings.

I’m almost afraid to ask for others’ experiences, because I’m sure there are some sad ones out there. But I think education about RMSF and the other tick-borne diseases is valuable and important. So please share if you are willing.

Kate and BooBoo’s Story: Rocky Mountain Spotted Fever? But We Live in NJ!

Resources

Lists of tick-borne diseases.

Rocky Mountain Spotted Fever in Humans

Rocky Mountain Spotted Fever in Dogs

Tick Safety

  • Do whatever you can to prevent tick exposure in the first place.
  • Check your dog thoroughly after possible exposures.
  • Remove any attached ticks quickly. Some tick-borne diseases are transferred quickly.
  • Get your dog to the vet if she has a fever or any of the symptoms listed here: Symptoms of Tick-Borne Diseases.
  • Oh yes, and be careful for yourself and human loved ones as well. There are cases of dog and humans simultaneously getting the disease because of concentrations of infected ticks in the same area.6)Paddock, Christopher D., et al. “Short report: concurrent Rocky Mountain spotted fever in a dog and its owner.” The American journal of tropical medicine and hygiene 66.2 (2002): 197-199. 7)Elchos, Brigid N., and Jerome Goddard. “Implications of presumptive fatal Rocky Mountain spotted fever in two dogs and their owner.” Journal of the American Veterinary Medical Association 223.10 (2003): 1450-1452. If you are in the U.S., check the incidence map in this article to see how prevalent it is in your state. RMSF is not found outside the Americas, but there are other related spotted fevers found in most parts of the globe.

© Eileen Anderson 2014                                                                                                             eileenanddogs.com

Notes   [ + ]

1. Comer, K. M. “Rocky Mountain spotted fever.” The Veterinary clinics of North America. Small animal practice 21.1 (1991): 27-44.
2. Harrus, S., et al. “Rickettsiales.” Pathogenesis of Bacterial Infections in Animals, Third Edition (2004): 425-444.
3. Comer, K. M. “Rocky Mountain spotted fever.” The Veterinary clinics of North America. Small animal practice 21.1 (1991): 27-44.
4. Keenan, K. P., et al. “Studies on the pathogenesis of Rickettsia rickettsii in the dog: clinical and clinicopathologic changes of experimental infection.” American journal of veterinary research 38.6 (1977): 851-856.
5. Bakken, Johan S., et al. “Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis—United States.” MMWR Morb Mortal Wkly Rep 55 (2006): 1.
6. Paddock, Christopher D., et al. “Short report: concurrent Rocky Mountain spotted fever in a dog and its owner.” The American journal of tropical medicine and hygiene 66.2 (2002): 197-199.
7. Elchos, Brigid N., and Jerome Goddard. “Implications of presumptive fatal Rocky Mountain spotted fever in two dogs and their owner.” Journal of the American Veterinary Medical Association 223.10 (2003): 1450-1452.