Rickettsial Infections

Rickettsial (rih-KET-see-ul) infections are a collection of diseases caused by bacteria from the Rickettsiaceae family.


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Brill-Zinsser disease


Murdne typhus

Q fever


Rocky Mountain sponted fever


What Are They?

The diseases caused by rickettsial infections are alike in many ways. Rocky Mountain spotted fever, typhus (TY-fis), ehrlichiosis (air-lik-e-O-sis), and Q fever all have similar symptoms, including headache, high fever, and sometimes a rash. These infections also respond to the same type of treatment, and many of them spread in the same way: through the bites of blood-sucking arthropods * , such as lice, fleas, and ticks.

How Common Are Rickettsial Infections?

These infections do not occur frequently in the United States (although typhus is relatively common in other parts of the world, especially the tropics). Rocky Mountain spotted fever is the most common rickettsial infection in the United States: up to 1,200 cases are reported yearly. Fewer than 100 typhus cases are reported annually, and a total of about 1,200 cases of ehrlichiosis have been reported during an 11-year period.

Are They Contagious?

Rickettsial infections do not spread directly from person to person. Instead, most require blood-sucking arthropods, such as lice, ticks, and fleas, to carry the organisms between animals and people or from one person to another. When a flea, for example, bites an infected animal or person, it can ingest the infectious bacteria. If the flea then bites someone else, it can spread the disease to that person. In the case of Rocky Mountain spotted fever, however, the bacterium lives and reproduces within ticks. Once a tick acquires the bacterium (from its mother when it is still an egg or through mating or feeding on an infected animal) it can infect people for the rest of its life. Q fever mainly spreads from livestock animals to people. The bacteria can pass into the animals' bowel movements, milk, urine, or fluids that accompany giving birth. People become infected by breathing in the bacteria in airborne bits of dust contaminated with one of those substances.

* arthropods are members of a group of organisms that lack a spinal column and have a segmented body and jointed limbs. This group includes various insects, ticks, spiders, lice, and fleas.

Specific Infections

Rocky Mountain spotted fever

Rocky Mountain spotted fever first was recognized in the Rocky Mountain states (such as Idaho, Montana, and Colorado) but since then it has been found throughout the United States. It is caused by the Rickettsia rickettsii bacterium, which is transmitted by tick bites. The disease is most common in children, usually in tick-infested areas, where outdoor work and play create the most risk.

Symptoms of infection include a severe headache, muscle pain, chills, fever, confusion, and a rash that appears first on the wrists and ankles before spreading. About 5 percent of Rocky Mountain spotted fever cases are fatal, usually because a person does not receive treatment quickly.


Typhus can appear in several forms, including epidemic * typhus, murine typhus, and Brill-Zinsser disease. The bacteria that cause typhus, Rickettsia prowazekii and Rickettsia typhi, spread to people through the bites of fleas or lice. People who are infected can become very sick and often have a fever that may climb as high as 105 to 107 degrees Fahrenheit. Murine typhus is the variety seen most often in the United States, usually in the southern and southeastern states. People who come into contact with fleas that feed on rats, opossums, and outdoor cats are at the greatest risk for the disease. Once someone becomes infected, that person may experience a headache, a rash, nausea (NAW-zee-uh), joint pain, belly pain, vomiting, and a dry cough. The disease is rarely fatal. Most people recover with few complications.

* epidemic (eh-pih-DEH-mik) is an outbreak of disease, especially infectious disease, in which the number of cases suddenly becomes far greater than usual. Usually epidemics are outbreaks of diseases in specific regions, whereas worldwide epidemics are called pandemics.

* stupor is a state of sluggishness or impaired consciousness.

* delirium (dih-LEER-e-um) is a condition in which a person is confused, is unable to think clearly, and has a reduced level of consciousness.

* vaccinations (vak-sih-NAY-shunz), also called immunizations, are the giving of doses of vaccines, which are preparations of killed or weakened germs, or a part of a germ or product It produces, to prevent or lessen the severity of a disease.

Historical Importance
of Typhus

Epidemic typhus has a long history of causing death in times of war. Poor sanitation and the presence of lice and rats in crowded living quarters have contributed to high rates of illness and death among soldiers: During the Napoleonic War, the French defeat in Russia in 1812 was attributed to typhus. Conditions were no better by World War I: Thousands of soldiers had fallen victim to typhus by the war's end. It was not until the time of World War II that the disease could be controlled with vaccinations * , antibiotics, and more sanitary conditions. Typhus also has been referred to as "jail fever," because epidemics would periodically sweep through prisons, where filthy conditions made a home for rats and lice.

Murine typhus is a milder form of epidemic typhus, which is associated with a drop in blood pressure and stupor * or delirium * , and it can be fatal. Epidemic typhus is spread from person to person by body lice. Brill-Zinsser disease is a recurrence of epidemic typhus that appears in someone who was infected before that person's immune system was weakened by stress or illness. When the body's defenses are down, organisms left over from the earlier bout of illness may reactivate. The disease causes mild symptoms and is not fatal.

Q fever

Q fever is caused by the bacterium Coxiella burnetii, which lives primarily in farm animals, such as sheep, goats, and cattle. People who contract the infection may have no symptoms at all or may experience symptoms similar to those of the flu, such as fever, muscle and joint aches, severe headache, and dry cough. Nausea, vomiting, diarrhea (dyeuh-REE-uh), chest and belly pain, and jaundice * also can accompany Q fever. People who work with animals, such as veterinarians, farmers, and slaughterhouse workers, are most at risk for the disease, which is contracted by breathing in the bacteria from the animals' bowel movements, milk, urine, or fluids from giving birth.


Ehrlichiosis is caused by infection with the species of Ehrlichia (air-LIH-kee-uh) bacteria E. chaffeensis and E. phagocytophila. Tick bites spread the bacteria to people, where the infection produces symptoms similar to those of Rocky Mountain spotted fever. Severe cases can damage many organ systems and lead to seizures * , coma and death.

How Do Doctors Make the Diagnosis?

Rickettsial infections are diagnosed by finding antibodies * to the organism in the blood. These antibodies usually are not present early in the illness, so a doctor relies on the patient's history of symptoms, a physical examination, and information about where the person lives or became sick to make the diagnosis. To avoid potentially serious complications, it is important not to delay treatment of rickettsial infections while waiting for test results. In some cases, a skin biopsy * of the rash can aid in making the diagnosis.

What Is the Treatment for Rickettsial Infections?

All of these diseases are treated with antibiotics. Patients begin taking the medication as soon as possible, because a delay in treatment may increase the risk of complications. In more serious cases, often those in which the diagnosis has been delayed, it may be necessary to hospitalize patients and treat them with intravenous * (IV) antibiotics and fluids.

How Long Does a Rickettsial Infection Last?

The infections typically last from 1 week to several weeks. If they go untreated or if treatment does not begin soon after infection, the disease can linger for months.

* jaundice (JON-dis) is a yellowing of the skin, and sometimes the whites of the eyes, caused by a buildup in the body of bilirubin, a chemical produced in and released by the liver. An increase in bilirubin may indicate disease of the liver or certain blood disorders.

* seizures (SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.

* coma (KO-ma) is an unconscious state in which a person cannot be awakened and cannot move, see, speak, or hear.

* 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.

* intravenous (in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.

* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.

What Are the Complications?

Untreated and severe cases of any of these diseases can be fatal. In addition, each rickettsial illness has its unique complications:

  • Rocky Mountain spotted fever can cause paralysis * , hearing loss, and nerve damage.
  • Typhus can lead to pneumonia * , kidney * problems, and problems with the central nervous system * .
  • Chronic * Q fever in the elderly can cause endocarditis * and hepatitis * .
  • Ehrlichiosis can damage various organs, including the lungs, kidneys, and brain.

How Are Rickettsial Infections Prevented?

People can take steps to protect themselves from infection by avoiding flea, tick, and louse bites. It is recommended that anyone who works or plays outdoors be particularly careful. Avoiding areas that are infested with lice, ticks, and fleas or using insecticides and repellents in those areas can help. Wearing long pants and long-sleeved shirts, especially in spots with thick bushes or tall grass, also can guard against bites. After spending time outside in areas where ticks are found, people should examine their bodies carefully, including the hair, to make sure that there are no ticks. It is wise to check pets regularly for ticks, too, because animals can carry parasites into the house.

Q fever is best prevented by regularly testing animals for infection and isolating those that are infected. Doctors recommend that people who work with animals wash hands and launder clothes carefully to lower their risk of infection.

* pneumonia (nu-MO-nyah) is inflammation of the lung.

* kidney is one of the pair of organs that filter blood and remove waste products and excess water from the body in the form of urine.

* central nervous (SEN-trul NER-vus) system is the part of the nervous system that includes the brain and spinal cord.

* chronic (KRAH-nik) means continuing for a long period of time.

* endocarditis (en-do-kar-DYE-tis) is an inflammation of the valves and internal lining of the heart, known as the endocardium (en-doh-KAR-dee-um), usually caused by an infection.

* hepatitis (heh-puh-TIE-tis) is an inflammation of the liver. Hepatitis can be caused by viruses, bacteria, and a number of other noninfectious medical conditions.

See also
Endocarditis, Infectious
Hepatitis, Infectious
Rocky Mountain Spotted Fever
Tick-borne Infections



U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. Through the website of the National Center for Infectious Diseases, the CDC provides fact sheets and other information on rickettsial infections.
Telephone 800-311-3435


KidsHealth.org . KidsHealth is a website created by the medical experts of the Nemours Foundation and is devoted to issues of children's health. It contains articles on a variety of health topics, including Rocky Mountain spotted fever.

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