Rocky Mountain spotted fever (RMSF) is a bacterial disease spread through the bite of an infected tick. It is one of the deadliest tick-borne diseases in the Western Hemisphere. Early recognition and treatment are keys to successful recovery.
How common is RMSF?
It is relatively rare. There are usually fewer than 20,000 cases of RMSF per year in the US.
How is RMSF transmitted to humans?
The bacteria that causes RMSF (Rickettsia rickettsii) is spread by several species of ticks in the US, including the American dog tick, the brown dog tick, and the Rocky Mountain wood tick.
If a tick is attached to your skin for 6-10 hours, you may pick up this infection. This is significantly less time than it usually takes to transmit Lyme disease.
RMSF primarily occurs in warm weather when the ticks that spread the disease are most active.
Where is RMSF most common?
Although it was first identified in the Rocky Mountains, RMSF cases occur throughout the U.S., most commonly in North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma. It also occurs in parts of Canada, Mexico, and in Central and South America.
What are the signs and symptoms of RMSF?
Signs and symptoms may start between 2 and 14 days after tick exposure. Early signs and symptoms are nonspecific, including fever and headache. But this infection can rapidly progress to a serious, life-threatening illness. Symptoms include:
- Fever, chills, body aches
- Rash –
- Usually starts 2-5 days after fever begins.
- The appearance of the rash can vary quite a bit over the course of the illness. It can be red splotches, or pinpoint dots that are red or purple.
- It usually starts on the wrists and ankles, then can spread all over, including to palms and soles.
- It is not itchy.
- Headache, which can be severe
- Nausea, vomiting, stomach pain, lack of appetite
How is RMSF diagnosed and treated?
RMSF can be hard to diagnose because the initial symptoms are nonspecific and similar to many other infections. There are blood tests that can be done to look for evidence of RMSF. Unfortunately, the results of these tests can take a long time to come back.
If your doctor is strongly suspicious that you have RMSF, they will recommend antibiotic treatment immediately, even before the test results come back, because people who are not treated within the first 5 days of developing symptoms can develop serious complications and even die from this infection.
Doxycycline is the most effective antibiotic for the treatment of RMSF. It is recommended for adults and children. The risks associated with RMSF infection are so high, and new research shows no evidence of tooth staining when doxycycline is used in children to treat RMSF, so it is the preferred treatment, even for kids. Use of antibiotics other than doxycycline increases the risk of severe illness and death.
What are the possible complications that can happen from RMSF?
This infection damages the lining of blood vessels, particularly smaller blood vessels. This can lead to several complications if the infection is not treated early. These complications include:
- Encephalitis – Inflammation of the brain
- Meningitis – Inflammation of the spinal cord and spinal fluid
- Inflammation of the heart or lungs
- Kidney failure
- Serious damage to blood vessels leading to gangrene in arms or legs.
- Death – If not treated, the death rate is about 80%.
Can RMSF cause long-term health problems?
Yes. Because of the complications, some patients who recover from RMSF can be left with permanent health problems or disability. These include:
- Amputations – Arms, legs, fingers, or toes may need amputation.
- Hearing loss
- Mental disability
Any permanent damage that is present is caused by complications of the acute infection. There is no chronic or persistent infection with RMSF.
How can you prevent RMSF?
Preventing tick bites and checking for ticks on people and pets daily is key. We talked more about this 2 weeks ago. If you missed that article, check your email or use this link: Preventing Tick Bites – eDocAmerica
If you have any questions about Rocky Mountain Spotted Fever, please log into your account and send us your question. We are here to help.
Dr. Anita Bennett MD – Health Tip Content Editor