Lyme Disease Versus Rocky Mountain Spotted Fever

When we think of ticks, we most often think of Lyme disease. While Lyme is the most common vector-borne disease, infecting more than 476,000 people in the U.S. alone each year, unfortunately it is not the only tick-borne disease. There are many types of ticks that carry different infectious disease-causing pathogens. All of them are a public health threat, particularly as tick populations spread and grow due to factors like climate change. Let’s walk through different types of tick species and the diseases they can spread, and focus on the differences and similarities between Lyme disease and Rocky Mountain Spotted Fever (RMSF).

What are the different types of ticks?

Different types of ticks carrying different pathogens are found in various geographic regions. Black-legged ticks, sometimes referred to as deer ticks, are the only type of ticks that transmit Lyme disease (as well as other tick-borne infections, discussed below). Other types of ticks include the lone star tick, the American dog tick, the Rocky Mountain wood tick, the soft tick, the brown dog tick, and the longhorned tick. For more information on each of these ticks including what they look like, where they’re found, and which tick-borne illnesses they can transmit, see GLA’s Tick Table.

While Lyme disease is spread by the black-legged tick, Rocky Mountain Spotted Fever is spread by the American dog tick, the Rocky Mountain wood tick, and the brown dog tick. Black-legged ticks are found all across the U.S., particularly in the Northeast and upper Midwest and the Pacific coast (there, the black-legged tick is called the western black-legged tick). The American dog tick is found East of the Rocky Mountains, and in areas of the Pacific coast. The Rocky Mountain wood tick is found in Rocky Mountain states, and the brown dog tick is found throughout the U.S.

Despite its name, it’s important to know that Rocky Mountain Spotted Fever is not exclusive to the Rocky Mountains or to the ticks that live there!

What are other tick-borne illnesses?

Other tick-borne illnesses are sometimes referred to as co-infections, because you can get them along with Lyme disease (if your tick bite is from an infected black-legged tick) or you can get them apart from Lyme (if they are transmitted by a different type of tick, or if you the black-legged tick that bites you is carrying other pathogens but not borrelia burgdorferi, the bacterium that causes Lyme).

In addition to or instead of Lyme disease, black-legged ticks can also transmit the infections anaplasmosis, babesiosis, ehrlichiosis, tick-borne relapsing fever, Powassan encephalitis, tick-borne encephalitis, and possibly Bartonella henselae (cat-scratch fever).

In addition to Rocky Mountain Spotted Fever, the dog tick and Rocky Mountain wood tick can transmit tularemia.

For more on co-infections including their symptoms, see GLA’s Common Tick-Borne Diseases page.

Differences between Lyme Disease and Rocky Mountain Spotted Fever

The two tick-borne diseases that we’re focusing on here, Lyme and Rocky Mountain Spotted Fever, have similarities but also important bacterial and symptom differences.

Bacterial differences

Lyme disease is caused by the bacteria borrelia burgdorferi. Rocky Mountain Spotted Fever comes from a bacteria group known as ricksettia; RMSF is caused by Ricksettia ricksettsii (r. ricksettsii). Which illness you develop depends on the type of tick that bit you and the types of pathogens it was carrying. (If you save the tick, you can send it for testing at a tick testing laboratory.)

Symptom differences

Though some symptoms of Lyme disease and Rocky Mountain Spotted Fever can overlap, and both can be difficult to diagnose because their symptoms can overlap with many other illnesses, here are specific early symptoms for each illness.

Lyme Disease

• Fever
• Fatigue
• Aches
• Chills
• Swollen lymph nodes
• Headache
• Other flu-like symptoms
• Erythema migrans (EM) rash (though not everyone gets or notices Lyme disease rashes, and they don’t always look like a bullseye).

Rocky Mountain Spotted Fever

• Nausea and vomiting
• Stomach pain
• Lack of appetite
• Rash (reddish-to-black, resembling measles, though not everyone gets the rash)
• Muscle pain
• Fever
• Headache

Treatment Differences

Both Lyme disease and Rocky Mountain Spotted Fever are treated with antibiotics, usually doxycycline, though other antibiotics can be used depending on factors like age, pregnancy, and tolerance. Healthcare providers may also suggest over-the-counter treatments like pain reliever, hydrocortisone or other anti-itch cream to manage symptoms like fever, headache, and rash.

Early diagnosis and immediate antibiotic regimens are critical for treating Lyme and Rocky Mountain Spotted Fever. If untreated or under-treated, both bacterial diseases can cause the following long-term complications:

Lyme disease

• Facial palsy
• Lyme arthritis
• Lyme carditis
• Numbness or tingling in the hands or feet
• Severe, extreme fatigue
• Cognitive impairment including brain fog, vertigo, and dizziness
• Difficulty sleeping

Rocky Mountain Spotted Fever

• Damage to blood vessels that may lead to amputation of arms, legs, fingers, or toes
• Hearing loss
• Paralysis
• Mental disability

Avoiding Ticks

It’s good to understand the differences in these diseases, but the real question is how to prevent them. The rise and spread of tick populations is an environmental health problem. Ticks are spread not just by deer but by small mammals like mice, shrews, chipmunks and birds. Ticks like to live in moist, shady places like wood piles, leaf litter, long grass, beach grass, bushy areas, stone walls, and perimeters where the lawn meets the woods. If you spend time outdoors, you are at risk for a tick bite and should take proper prevention measures; prevention is currently the best method of tick-borne disease control.

The best way to avoid a tick bite is to Be Tick AWARE:

• Avoid areas where ticks live.
• Wear light colored clothing to spot ticks more easily, such as a long-sleeved shirt tucked in at the waist, long pants tucked into high socks, closed-toed shoes, and a hat with your hair tucked in. Do not walk in the grass barefoot or in open sandals, even if it’s a shortcut.
• Apply EPA-approved insect repellent such as picaridin or DEET to skin, and insecticide such as permethrin to clothing and shoes as directed.
• Remove clothing upon entering the home and toss into dryer on high heat for 10-15 minutes to kill live ticks (just tossing them in the washer won’t work).
• Examine yourself and your pets for ticks daily. To do a proper tick check, feel for bumps, paying close attention to the backs of knees, the groin, the armpits, in and behind the ears, in the belly button, and the scalp.

If you do get a tick bite, remove it immediately, contact your doctor, and monitor your symptoms.

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The above material is provided for information purposes only. The material (a) is not nor should be considered, or used as a substitute for, medical advice, diagnosis, or treatment, nor (b) does it necessarily represent endorsement by or an official position of Global Lyme Alliance, Inc. or any of its directors, officers, advisors or volunteers. Advice on the testing, treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient’s medical history.