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Rocky Mountain Spotted Fever

Childhood Infections

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Updated April 05, 2007

An American dog tick, which can infect your child with Rocky Mountain spotted fever if it bites him.

An American dog tick, which can infect your child with the Rickettsia rickettsii bacteria that causes Rocky Mountain spotted fever if it bites him.

Photo courtesy of James Gathany and the CDC.
Rocky Mountain spotted fever is a bacterial infection spread by the bite of a tick. Other tick-borne illnesses include Lyme disease, tularemia, babesiosis, Colorado tick fever and ehrlichiosis.

Rocky Mountain spotted fever is perhaps not as well known by patients or pediatricians as Lyme disease though, which is unfortunate, since complications can include gangrene, arrhythmias, renal failure and more. Also, it can be fatal, especially if treatment is not started early.

Although small numbers of cases have been reported in almost every state in the United States, most cases occur in the southeastern U.S., especially North Carolina, Tennessee, South Carolina, Georgia, Maryland, Arkansas, Virginia, and Oklahoma. It is most often transmitted by the American dog tick, which can carry the Rickettsia rickettsii bacteria.

Symptoms

Symptoms of Rocky Mountain spotted fever typically begin about 5 to 7 days after getting bitten by a tick (the incubation period). Initial symptoms are a headache, malaise, anorexia, and muscle aches (myalgias), which can be followed by:
  • fever*
  • chills
  • headache*
  • vomiting*
  • diarrhea
  • abdominal pain
  • nausea
  • worsening muscle aches
(*classic symptoms of Rocky Mountain spotted fever)

A rash is another classic symptom of Rocky Mountain spotten fever, and it usually begins on the wrists and ankles and then spreads to the arms, legs, and the rest of the child's body, including their palms and soles. The rash of Rocky Mountain spotted fever can become hemorrhagic and the skin in affected areas sometimes desquamates (peels off). Although characteristic for Rocky Mountain spotted fever, the rash may not begin until your child has already been sick with other symptoms for 3 to 5 days. Without treatment, the symptoms of Rocky Mountain spotted fever may last 10 days to a few weeks.

Diagnosis

Unfortunately, the symptoms of Rocky Mountain spotted fever mimic many viral infections, which can make the diagnosis difficult to make.

The diagnosis of Rocky Mountain spotted fever should be considered in a child with classic symptoms, especially if they had a tick bite and live in or recently visited an area where it commonly occurs. Surprisingly, up to 40 percent of people with Rocky Mountain spotted fever don't report a recent tick bite.

Testing for the antibodies to Rickettsia rickettsii is possible, but should not delay treatment when a diagnosis is strongly suspected, especially since they may not become positive until after your child has been sick for at least a week. A biopsy of the skin rash can also be done to help diagnose Rocky Mountain spotted fever, as can other tests, including PCR assays.

Nonspecific signs of Rocky Mountain spotted fever can include hyponatremia (low blood sodium levels), anemia (low red blood cell levels), thrombocytopenia (low blood platelet levels), elevated muscle enzymes, jaundice (yellowing of the skin and eyes), and elevated liver function tests.

Treatments

Antibiotics are the main treatments for Rocky Mountain spotted fever, including tetracycline, doxycycline, and chloramphenicol. Since tetracycline can cause tooth staining in young children, and chloramphenicol has many side effects, doxycycline is usually the antibiotic of choice for most children with Rocky Mountain spotted fever.

Supportive care and hospitalization may also be needed for children with severe cases of Rocky Mountain spotted fever.

What You Need To Know

  • Rocky Mountain spotted fever is also known as RMSF or tick-borne typhus and is probably underdiagnosed.

  • About one half of cases of Rocky Mountain spotted fever occur in children.

  • The peak time of year for reported cases of Rocky Mountain spotted fever is April to September, although it can occur year round.

  • Although the average incubation period is 5 to 7 days, it can be as short as 2 days to as long as 14 days from when your child is bitten by a tick.

  • Rocky Mountain spotted fever is not contagious between people.

  • You should take steps to avoid ticks and inspect your child for ticks each day if your child has been outside and you live in an area where tick-borne infections, such as Rocky Mountain spotted fever, Lyme disease, or ehrlichiosis, are common.

  • Doxycycline can cause tooth staining, but not usually in the single course of treatment that is required for most younger kids with Rocky Mountain spotted fever.

Most importantly, tell your pediatrician if your child had a tick bite and then develops any symptoms in the following week or two, especially a fever, rash, headache, nausea or vomiting. Your pediatrician will be less likely to say "it is just a virus" if reminded about a recent tick bite...



Sources:

Gershon: Krugman's Infectious Diseases of Children, 11th ed.

Long: Principles and Practice of Pediatric Infectious Diseases, 2nd ed.

Behrman: Nelson Textbook of Pediatrics, 17th ed.

Clinical and laboratory features, hospital course, and outcome of Rocky Mountain spotted fever in children. Buckingham SC - J Pediatr - 01-FEB-2007; 150(2): 180-4, 184.e1

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