Rocky Mountain Spotted Fever – even out here on the prairie

Farm Forum

By many reports, this spring and early summer have been as bad a season for ticks as ever. I’ve observed that ticks create a huge “ick” reaction for most people when they find one crawling on them or attached to a pet. They are nasty looking creatures, no doubt. I guess over all the years of dealing with tick-infested dogs and other animals coming into the vet clinic, my reaction upon finding them have become more ho-hum than that of most of my friends and acquaintances.

Beyond the creepiness quotient, there are legitimate reasons to dislike these little crawly critters. Ticks are potential carriers of many diseases that can affect animals as well as people. Rocky Mountain Spotted Fever (RMSF) is one of those diseases. It might not get the press that Lyme disease gets, but essentially every year in South Dakota there are people that get sick from this disease. While it was first noticed in (obviously) the Rocky Mountain states, RMSF has become established over a wide area of the Western Hemisphere.

The culprit (besides the tick) in RMSF is the bacteria called Rickettsia rickettsiae. This is one of a family of very unique infectious agents, the rickettsia. Most bacteria can live in a myriad of environments, but rickettsia can only be found in two places: within the cells of an animal (or human) or living free in the gut of an insect-not out in the environment. For this germ, its preferred vectors are the dog tick and wood tick, among the most commonly found ticks in this area.

Young ticks pick up this bacteria when they feed on an infected animal. They then pass it on to other animals during feeding, and the cycle continues. What’s more, if these infected ticks have baby ticks, it’s transmitted right along to the youngsters.

Four or five days after a dog is bitten by a tick infected with the RMSF bacteria, the animal will show signs of illness like high fever (105), swollen glands, stiff joints, and maybe some vomiting or diarrhea. The bacteria likes to infect and damage the cells that make up small blood vessels, so in some cases the resulting leaking blood and fluid causes edema or swelling of the face or extremities. Some dogs might get rashes inside their mouths or on the whites of their eyes. (You’ve noticed I’ve been talking about dogs; cats almost never get RMSF).

For people, the symptoms are fever, aches, and fatigue. About six days after the fever, rashes may appear on the wrists, arms, or ankles (hence the “spotted fever” part of the disease name). The symptoms then may get more severe with vomiting and stomach cramps.

For both dogs and people, the disease is not highly fatal. The tricky part tends to be in the diagnosis. As you can imagine, the signs and symptoms of RMSF are similar to a lot of different ailments (flu, for example), so the diagnosis often gets missed initially by veterinarians as well as physicians. It can be confirmed by blood tests, but oftentimes the tests are negative in the early stages of disease. In both dogs and people, RMSF can be successfully treated with antibiotics.

Even though both dogs and people can be affected by RMSF, one is not able to give it to the other. However, because dogs are quite susceptible to RMSF, many experts consider them to be like “canaries in the coal mine” for human infections: if it is recognized in dogs, then we know infected ticks are in the area that can affect people. The wide distribution of RMSF is just one reason why people should take care to protect themselves and their dogs from ticks (there are several good tick products out there for dogs, available through your veterinarian).

Rocky Mountain Spotted Fever is perhaps a unique example of the “One Health” principle. “One Health” is a way of looking at health that essentially states people and animals are all “in this together” when it comes to our susceptibility to certain infectious diseases and environmental changes.

Make sure you consider tick prevention for you and your dog as you go about your summer.

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via e-mail at or at 605-688-5171.