Tick-Borne Illnesses: Overview

A tick-borne illness is an infection that is transmitted through the bite of a tick.

What Are Tick-Borne Illnesses?

Some tick-borne diseases are specific to certain regions of the country, such as Colorado tick fever, which is seen in the Rocky Mountain states at elevations of 4,000 to 10,500 feet, whereas others can be found throughout the country, such as tularemia. Tick-borne illnesses are often linked to a certain kind of tick. For example, the lone star tick can carry ehrlichiosis but not Lyme disease. Some species of ticks can carry more than one type of disease, however, so a person can contract two different illnesses after being bitten by just one tick. This is called co-infection.

Magnified image of a tick.

Magnified image of a tick.

Some of the more common tick-borne illnesses include the following:


Several types of bacteria in the genus Ehrlichia (air-LIH-kee-uh) cause ehrlichiosis. In the United States, the primary source of infection is the lone star tick. People have long known that ehrlichiosis causes disease in animals, but the first case in humans in the United States was not identified until the 1980s. Ehrlichiosis is most often found in the mid-Atlantic, southeastern, and south central states.

Symptoms of ehrlichiosis resemble those of the flu: fever, chills, extreme tiredness, headache, muscle and joint pain, nausea, and vomiting.

There is usually no rash in adults, but up to 60 percent of children develop one. Some people have no symptoms or only mild symptoms. Complications, although rare, can occur in the elderly and people with weakened immune systems.


Anaplasmosis is similar to ehrlichiosis but is transmitted by a different species of tick and occurs in a different region of the United States. It was previously known as an ehrlichiosis called human granulocytic ehrlichiosis (HGE). It is spread by the blacklegged and western blacklegged ticks and occurs most frequently in the upper Midwest and northeastern United States.

The incubation period for anaplasmosis is one to two weeks. Symptoms of anaplasmosis resemble those of the flu: fever, shaking, chills, extreme tiredness, headache, muscle and joint pain, nausea, vomiting, diarrhea, poor appetite, and cough. In rare cases, a rash is seen. Few people develop all the symptoms, and the number and combination of symptoms varies from person to person. If not treated properly, anaplasmosis can be fatal, even in previously healthy people.


Babesiosis is a rare disease that appears mainly in the northeastern United States. It spreads through the bite of a deer tick that has been infected with a Babesia (buh-BE-she-uh) parasite, which attacks red blood cells. Because the deer tick also can spread Lyme disease, some people become infected with both diseases at the same time.

In healthy people, babesiosis infection may cause no symptoms. In others, early symptoms are extreme tiredness, lack of appetite, and a general feeling of being sick. Later symptoms include high fever, sweating, muscle aches, headache, and dark urine. The symptoms of babesiosis are similar to those of malaria * . Infected people may also have anemia * because of the parasite's attack on their red blood cells. The disease is not often fatal, but it can cause complications in the elderly, pregnant women, people with weakened immune systems, and people who have had their spleen removed.

The life cycle of a tick takes 2–3 years to complete. In the spring, eggs hatch into larvae, which feed on mice, birds, and small mammals until the fall, when they become dormant.

The life cycle of a tick takes 2–3 years to complete. In the spring, eggs hatch into larvae, which feed on mice, birds, and small mammals until the fall, when they become dormant. The following spring they molt into nymphs, which feed through the summer and then become adults in the fall. At any of these stages of growth, ticks may become infected with bacteria or other disease-causing agents by feeding on infected animals; as adults they may feed on humans and transmit the bacteria that cause the disease.
Illustration by Molly A. Moore Blessington. © 2016 Cengage Learning®.
Did You Know?

In the United States, there are at least 14 diseases that are caused by ticks, including anaplasmosis (an-ah-PLAZmo-sis), ehrlichiosis (air-lik-e-O-sis), babesiosis (bah-bih-sye-OH-sis), Borrelia miyamotoi (bo-REL-ee-ah MEE-ah-mo-TOY), Colorado tick fever, Heartland virus, Lyme (LIME) disease, Powassan disease (PO-wahs-ON), Rickettsia parkeri rickettsiosis (REE-ket-see-ah PARK-air-ee REE-ketsee-OH-sis), Rocky Mountain spotted fever, southern tick–associated rash illness, tick-borne relapsing fever, tularemia (TOO-la-ree-MEE-ah), and 364D rickettsiosis.

Lyme disease

Lyme disease gets its name from the town in Connecticut where doctors discovered the disease in 1975. It is the most common tick-borne illness in the United States. The majority of cases appear in the northeastern, north central, and northwestern states.

The bacterium Borrelia burgdorferi (buh-REEL-e-uh burg-DOR-feree), transmitted through deer ticks, causes Lyme disease. In some cases, the first sign of infection is the erythema migrans (air-uh-THEE-muh MY-granz) rash. It usually appears at the site of the tick bite, although it can develop anywhere on the body. The rash can be round, oval, or shaped like a bull's-eye with a red center surrounded by a clear area and then by a ring of red. Other early signs of the disease, such as extreme tiredness, headache, muscle aches, and fever, are similar to those of many infections, making diagnosis difficult. Not everyone who has Lyme disease develops the rash, and some people never show any symptoms.

If untreated, the infection spreads from the bloodstream further into the body. This can cause a variety of symptoms, including headaches, a stiff neck, tingling or numbness in the arms and legs, severe fatigue, painful joints, and a facial paralysis similar to Bell's palsy * . Lyme disease is not usually fatal, but if left unchecked, it can lead to complications that can last for years, such as arthritis, confusion, a lack of coordination, mood disorders, vision problems, and even heart issues.

Rocky Mountain spotted fever

Despite its name, most cases of Rocky Mountain spotted fever (RMSF) are not found in the Rocky Mountains but in the southeastern states. Cases also appear throughout the continental United States and in Canada, Mexico, and Central and South America. RMSF is one of the most dangerous tick-borne infections because it can be difficult to diagnose and has severe complications. Caused by the Rickettsia rickettsii (rih-KET-see-uh rih-KET-see-eye) bacterium, the disease spreads to humans through bites from the wood tick, dog tick, and lone star tick.

Symptoms of RMSF include high fever, headache, aching in the muscles, nausea and vomiting, and diarrhea. A rash may appear first at the wrists, ankles, palms, and soles and then on the forearms, neck, face, and trunk. If left untreated, the disease may lead to inflammation of the brain, heart, and/or lungs, kidney failure, and even death. Although incidences of RMSF have risen during the last decade, the fatality rate has fallen to fewer than 0.5 percent in cases where treatment is received.

How to Remove a Tick

Petroleum jelly, lit matches, nail polish, and other products do not help in tick removal and should not be used.

How Common Are Tick-Borne Diseases?

Lyme disease is the most commonly occurring tick-borne disease in the United States, with the Centers for Diseases Control and Prevention (CDC) reporting more than 25,000 confirmed cases in 2014. RMSF is the second most common type of tick-borne illness, with the CDC reporting approximately 2,000 cases in 2010.

In contrast to these diseases, anaplasmosis, ehrlichiosis, and babesiosis are less common, with about 1,700 cases of anaplasmosis in 2010, fewer than 800 cases of ehrlichiosis in 2010, and approximately 1,800 cases of babesiosis in 2013.

Who Is at Risk for Tick-Borne Diseases?

People who work or play in the outdoors are at risk for acquiring tick-borne diseases. Specifically people who spend time in wooded areas or areas with high grass or leaf litter are more likely to be exposed to ticks. It is important to note that the woods do not have to be deep; in fact, patchy, broken-up forests in suburban areas often have a higher concentration of ticks than dense woods. This is because smaller patches of woods tend to have fewer predator animals, which leads to greater numbers of small rodents. These small rodents are one of the main food supplies for ticks.

Ticks are most active in the spring, summer, and fall but can be active year round in warmer climates. In the United States, ticks may even become briefly active in the winter if the temperature rises above 45ºF.

How Are Tick-Borne Diseases Diagnosed and Treated?


Diagnosing a tick-borne illness can be difficult because the symptoms of many of these illnesses resemble those of the flu or other infections. One of the best clues is a recent tick bite, but in many cases people do not even know they have been bitten. Tick nymphs are a particular concern in this regard because they are so small that they are barely visible.

Doctors often diagnose these diseases based on the patient's history of symptoms and activities, where the patient lives or became sick, and a physical examination that includes looking for rashes. A doctor may order a blood test to check for antibodies * to the organism causing the infection, but in some cases these tests are not able to detect the disease in its early stages. Skin biopsy * from a rash area may confirm a diagnosis.


Antibiotics are effective against the bacterial infections. Antiparasitic medicines work well for babesiosis. In most cases, patients recover at home. Sometimes, however, especially in cases of RMSF, patients may need hospitalization for more intensive antibiotic therapy and supportive care.

Can Tick-Borne Diseases Be Prevented?

Tick-borne diseases can be prevented by:

* .
  • Using products that contain permethrin on clothing, boots, tents, and other gear whenever hiking or working in wooded or bushy areas.
  • Bathing or showering within two hours of coming indoors to wash off and more easily find ticks.
  • Conducting a full-body tick check when returning from tick-infested areas. Particular attention should be paid to hard-to-see areas such as the groin, back of the knees, and armpits.
  • Examining gear and pets for ticks.
  • Tumbling clothes in a clothes dryer on high heat for at least one hour to kill any remaining ticks.
  • See also Lyme Disease • Rickettsial Infections • Rocky Mountain Spotted Fever • Tularemia


    Books and Articles

    Centers for Disease Control and Prevention. Tickborne Diseases of the United States, 3rd ed. Atlanta, GA: Centers for Disease Control and Prevention, 2015. http://www.cdc.gov/lyme/resources/TickborneDiseases.pdf (accessed April 8, 2016).

    Schaller, James, and Kimberly Mountjoy. What You May Not Know About Bartonella, Babesia, Lyme Disease and Other Tick & Flea-Borne Infections: Improving Treatment Speed, Recovery & Patient Satisfaction. New York: International University Infectious Disease Press, 2012.

    Spreen, Kathy. Compendium of Tick-Borne Diseases: A Thousand Pearls. Kindle Edition. West Chester, PA: Pocopson Publishing, LLC, 2014.


    Centers for Disease Control and Prevention. “Diseases That Can Be Spread from Pets to People.” http://www.cdc.gov/healthypets/diseases/index.html (accessed April 8, 2016).

    Centers for Disease Control and Prevention. “Preventing Tick Bites.” http://www.cdc.gov/ticks/avoid/on_people.html (accessed April 8, 2016).

    National Institute of Allergy and Infectious Diseases. “Tickborne Diseases.” http://www3.niaid.nih.gov/topics/tickborne (accessed April 8, 2016).


    American Lyme Disease Foundation. PO Box 466, Lyme, CT 06371. Website: www.aldf.com (accessed April 8, 2016).

    Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 800-CDC-INFO, 800-2324636. Website: www.cdc.gov (accessed April 8, 2016).

    Centers for Disease Control and Prevention, Division of Vector Borne Diseases (DVBD). 3150 Rampart Rd., Fort Collins, CO 80521. Toll-free: 800-CDC-INFO, 800-232-4636. Website: http://www.cdc.gov/ncezid/dvbd/ (accessed April 8, 2016).

    Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID). 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 800-CDC-INFO, 800-232-4636. Website: http://www.cdc.gov/ncezid/ (accessed April 8, 2016).

    * host is an organism that provides another organism (such as a parasite or virus) with a place to live and grow.

    * malaria (mah-LAIR-e-uh) is a disease spread to humans by the bite of an infected mosquito.

    * anemia (uh-NEE-me-uh) is a blood condition in which there is decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.

    * Bell's palsy (PAWL-zee) is a condition in which there is damage to the facial nerve, also called the seventh cranial nerve, causing weakness or loss of function of muscles on one side of the face.

    * antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

    * biopsy (BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.

    * DEET (abbreviation for N, Ndiethyl-meta-toluamide) is the active ingredient in many insect repellants.

      This information is not a tool for self-diagnosis or a substitute for professional care.