Rocky Mountain Spotted Fever - Causes, Symptoms and Treatments
Rocky Mountain spotted fever (RMSF) is a febrile, rash-producing illness caused by Rickettsia rickettsii. The disease is transmitted to humans by a tick bite. Endemic throughout the continental United States, RMSF is particularly prevalent in the southeast and southwest. Because RMSF is associated with outdoor activities, such as camping and backpacking, thc incidence of this illness is usually higher in the spring and summer. Epidemiologic surveillance reports for RMSF indicate that the incidence is also higher in children ages 5 to 9, men and boys, and whites.
RMSF is fatal in about 5% of patients, Mortality rises when treatment is delayed and in older patients.
Causes of Rocky Mountain Spotted Fever:
R. rickettsii is transmitted to a human or small animal by a prolonged bite (4 to 6 hours) of an adult tick - the wood tick (Dermacentor andersoni) in the west and by the dog tick (Dermacentor variabilis) in the east. Occasionally, it's acquired through inhalation or through contact of abraded skin with tick excreta or tissue juices. (This explains why people should not crush ticks between their fingers when removing them from other people and animals.) In most tick-infested areas, 1 % to 5% of the ticks harbor R. rickettsii.
Signs and symptoms of Rocky Mountain Spotted Fever:
The incubation period is usually about 7 days, but it can range from 2 to 14 days. Generally, the shorter the incubation time, the more severe the infection. Signs and symptoms, which usually begin abruptly, include a persistent temperature of 102 0 to 104° F (38.9° to 40° C); a generalized, excruciating headache; nausea and vomiting; and aching in the bones, muscles, joints, and back. In addition, the tongue is covered with a thick white coating that gradually turns brown as the fever persists and rises.
Initially, the skin may simply appear flushed. Between days 2 and 5, eruptions begin around the wrists, ankles, or forehead; within 2 days, they cover the entire body, including the scalp, palms, and soles. The rash consists of erythematous macules 1 to 5 mm in diameter that blanch on pressure; if untreated, the rash may become petechial and maculopapular. By the 3rd week, the skin peels off and may become gangrenous over the elbows, fingers, and toes.
The pulse is strong initially, but it gradually becomes rapid (possibly reaching 150 beats/minute) and thready.
Diagnosis of Rocky Mountain Spotted Fever:
Diagnosis is usually based on a history of a tick bite or travel to a tick-infested area and a positive complement fixation test (which shows a fourfold increase in convalescent antibody titer compared with acute titers). Blood cultures should be performed to isolate the organism and confirm the diagnosis.
Another common but less reliable antibody test is the Weil-Felix reaction, which also shows a fourfold increase between the acute and convalescent sera titer levels. Increased titers usually develop after 10 to 14 days and persist for several months.
Additional recommended laboratory tests consist of a platelet count for thrombocytopenia (12,000 to 150,OOO/ul) and a white blood cell count (elevated to 11,000 to 33,000/ul) during the 2nd week of illness.
Other conditions to consider are meningococcemia, rubeola, typhus, Lyme disease, and Q fever.
Treatment of Rocky Mountain Spotted Fever:
Treatment requires careful removal of the tick and administration of antibiotics, such as chloramphenicol or tetracycline, until 3 days after the fever subsides. Treatment also includes symptomatic measures and, in DIC, heparin and platelet transfusion.
Special considerations and Prevention tips:
When the patient recovers sufficiently, initiate patient teaching about disease prevention. Instruct the patient to report any recurrent symptoms to the doctor at once so that treatment measures may resume immediately. Advise the patient to avoid tick-infested areas (woods, meadows, streams, and canyons) if possible. If he can't avoid tick-infested areas, tell him how to protect himself from a prolonged tick bite. Advise him to inspect his entire body (including his scalp) every 3 to 4 hours for attached ticks, to wear protective clothing, such as a long-sleeved shirt, pants securely tucked into laced boots, and a protective head covering, such as a cap, and to apply insect repellant to exposed skin and even to his clothing. Offer printed and illustrated instructions, if available, that teach the patient and his family members or other caregivers how to correctly and safely remove a tick. Or show them how to use tweezers or forceps and how to apply steady traction to release the whole tick without leaving its mouth parts still in the skin. After the patient removes the tick, caution him not to handle it or its fragments. Finally, instruct him to clean his skin with alcohol at the point of attachment.
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