Rocky Mountain Spotted Fever

Rocky Mountain spotted fever is an acute infectious, febrile, and rash-producing illness that is associated with outdoor activities, such as camping and hiking. Rocky Mountain spotted fever is endemic throughout the continental United States. The disease is particularly prevalent in children ages 5 to 9; the mortality rate is 5% due to delayed diagnosis and treatment. Mortality is higher in males than females. As outdoor activities increase in popularity, so does the risk for contracting Rocky Mountain spotted fever - especially in the spring and summer months.

The usual incubation period is 7 days, but it can range from 2 to 12 days.

Causes

The Rickettsia rickettsii organism causes Rocky Mountain spotted fever. It's transmitted by the wood tick (Dermacentor andersoni) in the western United States and by the dog tick (D. variabilis) in the eastern United States. The rickettsial organism enters humans or small animals with the prolonged bite (4 to 6 hours) of an adult tick.

This disease occasionally is acquired through inhalation or through contact of abraded skin with tick excreta or tissue juices. (This is why a person shouldn't crush a tick between the fingers when removing it.) In most tick-infested areas, 1 % to 5% of the ticks harbor R. rickettsia.

Signs and symptoms

People with Rocky Mountain spotted fever get a sudden fever (which can last for 2 or 3 weeks), severe headache, tiredness, deep muscle pain, chills, nausea, and a characteristic rash. The rash might begin on the legs or arms, can include the soles of the feet or palms of the hands, and can spread rapidly to the trunk or the rest of the body.

Diagnostic tests 

Diagnosis is based on symptoms and past history of a tick bite. The appearance and characteristics of the rash are important. Skin samples and lab tests are usually done to rule out other conditions and confirm the diagnosis.

Treatment

In Rocky Mountain spotted fever, treatment requires careful removal of the tick and administration of doxycycline, except for those that are allergic or pregnant. Chloramphenicol or oral tetracycline is an alternative, but neither is recommended for pregnant women or children. The seriously ill patient requires intensive care and careful fluid administration to achieve tissue perfusion without pulmonary edema. Intubation and mechanical ventilation may be required. Hemodialysis, antiseizure medication, and treatment for hemorrhage and thrombocytopenia may be needed.

Contagiousness

RMSF is not contagious from person to person.

It's caused by an infection with bacteria that infect humans through tick bites. The longer a tick stays attached to the skin, the greater the chance of infection. Several hours of attachment are usually necessary.

Prevention

When walking or hiking in tick-infested areas, tuck long pants into socks to protect the legs, and wear shoes and long-sleeved shirts. Ticks will show up on white or light colors better than dark colors, making them easier to remove from clothing.

Remove ticks immediately by using a tweezers, pulling carefully and steadily. Insect repellent may be helpful. Because less than 1% of ticks carry this infection, antibiotics are not usually given after a tick bite if there is no evidence of disease.