Rocky Mountain Spotted Fever and Other Tick-Borne Illnesses


By Barry C. Fox, M.D., University of Wisconsin

Rocky Mountain spotted fever is a tick-borne illness. Its name is a misnomer since the disease can be found in many areas of the United States outside the Rocky Mountains. The American and brown dog ticks, and the Rocky Mountain wood tick, are the main vectors for this disease, the most common fatal tick-borne disease in the country.

Warning sign of ticks that is fastened on a tree in the forest.
It is not unusual for entire families to be affected by tick-borne illnesses at the same time. (Image: Gabor Tinz/Shutterstock)

Difficult Diagnosis of Tick-Borne Illnesses

It is not unusual to have family clusters of the disease since families are outdoors at the same time in areas where the ticks that are carrying this unique germ are located. The classic triad for many tick-related illnesses includes the tick bite, a fever, and a distinctive rash.

But from what is now known about ticks, it may be difficult to diagnose tick illness because either a person doesn’t remember they were bitten by a tick, or they get ill five to seven days later and don’t realize it was due to a tick, or the symptoms resemble many other illnesses, or early blood tests in the first week are usually negative.

For all tick-borne illnesses, a history of a known tick bite occurs in less than 50 percent of cases. Hence, epidemiological clues have to be taken into account: does the patient live in or visit in an environment where ticks are prevalent, and/or did they perform any ‘high risk’ activities like walking through tall grasses or gardening? If a doctor uses his/her clinical and diagnostic skills correctly and starts doxycycline right away, most patients will get better.

This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now, on Wondrium.

Heartland Virus Is Another Contender

Tick-borne illnesses can result from other germs. The Heartland virus is a newly identified phlebovirus that was first isolated in 2009 from two Missouri farmers who were hospitalized with fever, low white blood cell count, and low platelet counts. Based on the patients’ clinical findings and their reported exposures, their illness was suspected to be transmitted by ticks.

After this discovery, the Centers for Disease Control worked with local health authorities and learned that the Heartland virus was found in the Lone Star tick. This disease is relatively rare, but during the 2012–2013 season, six additional confirmed Heartland virus disease cases were identified.

Physicians should take into account the diagnosis of the Heartland virus in patients who develop a fever with low white blood cell and platelet counts, without a more likely explanation, and who have tested negative for Ehrlichia and Anaplasma, or who have not responded to doxycycline therapy.

Learn more about the dynamic world of infectious disease.

The One that Doesn’t Respond to Treatment 

Syringe and tick on top of a magnifier glass.
Unfortunately, some diseases, for example, the Southern Tick Associated Rash Illness (STARI), do not respond to traditional treatment. (Image: ju_see/Shutterstock)

Lastly, a tick-borne disease without a known cause. STARI stands for Southern Tick Associated Rash Illness, thought to be transmitted by the Lone Star tick. Those infected develop a bull’s-eye rash very similar to Lyme disease, but the illness does not respond to the antibiotics used to treat Lyme. 

Since the cause of STARI hasn’t been identified yet, there are no tests nor are there any definitive treatments. Currently, there do not appear to be any late after-effects such as those that may occur with Lyme.

Preventing Risk of Tick-Borne Illnesses

Preventing tick-borne illnesses can be difficult in certain areas, but risks can be reduced by following these steps: Avoid direct contact with wildlife—even if it’s cute—use insect repellents in heavily wooded and grassy areas, and wear treated clothing. 

Man spraying insect repellent on his legs.
Always remember to check for ticks after coming back from a high-risk area and use repellent for good measure. (Image: baranq/Shutterstock)

Several companies now make insect-repellent clothing lines that could be useful for hiking in wooded areas. These are usually treated with permethrin, which has been approved by the Environmental Protection Agency, or EPA, for use in clothing. 

People should check for ticks after they’ve been in areas at risk; if they find one on them that they can’t recognize, they can save it in order to identify it through the state health department. Note that ticks at very young stages are only about the size of a poppy seed. Wearing light-colored clothing can also make it easier for ticks to be seen.

Learn more about bacteria: heroes and villains.

Use Appropriate Products for Good Measure

One safety note, for someone who doesn’t like using the chemical DEET, the EPA has approved a natural formula made from lemon eucalyptus oil that targets mosquitos and ticks. Products with this plant-based oil can be found in many stores. The EPA has ruled DEET to be safe if used properly, but not in babies less than two months old and never in concentrations of more than 30 percent.

In 2010, Consumer Reports recommended six products—four of which contained DEET, one with picaridin, and one with lemon eucalyptus. All of these products repelled deer ticks and mosquitos for at least seven hours.

What about products that contain sunscreen mixed with DEET? Just realize that someone may be getting more DEET than they want if they reapply the sunscreen more often.

So, people should keep alert if they are in areas where ticks are prevalent, use precautions, and keep themselves and their loved ones well.

Common Questions about Rocky Mountain Spotted Fever and Other Tick-Borne Illnesses

Q: Why is the diagnosis of Rocky Mountain spotted fever difficult?

In the case of this tick-borne illness, around half of the time, people don’t remember being bitten by a tick which makes it harder for doctors to diagnose the disease. Also, the symptoms may show up five to seven days after the bite.

Q: What are the similarities between STARI and Lyme disease?

Both STARI and Lyme disease develop similar bull’s-eye rashes on the body. But unlike Lyme disease, STARI doesn’t have a definitive treatment.

Q: How can someone prevent becoming ill with these tick-borne illnesses?

Some ways to reduce the risk of getting a tick-borne illness are as follows: avoid direct contact with wildlife, use insect repellents in heavily wooded and grassy areas, and wear treated clothing. Also, wearing light-colored clothing will help with noticing the ticks.

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