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.
RMSF is caused by the bacterium Rickettsia rickettsii, which is carried by the American dog tick and the Rocky Mountain wood tick. When an infected tick bites a human, the disease is transmitted through the skin into the bloodstream. The bacteria multiply inside cells of the inner lining of small arteries causing inflammation, or vasculitis.
Symptoms and Signs
People with Rocky Mountain spotted fever get a sudden fever:
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.
The most important factor is a history of exposure to rick-infested environment. Serologic tests are often negative initially, and treatment shouldn't be delayed until a positive test is obtained. Indirect immunofluorescence assay is the most common test and a diagnostic titer of 64 or greater is detectable between days 7 and 14 of the illness. Latex agglutination may reveal a diagnostic titer of 128 or greater 1 week after onset. The only diagnostic test that is useful during the acute illness is immunohistological examination of a cutaneous biopsy of a rash lesion. Cultivation of rickettsia is feasible but seldom undertaken because necessary equipment isn't available in all facilities, testing can be costly, and the infection could spread to laboratory personnel.
Other laboratory test findings may include a decreased platelet count, white blood cell count, and fibrinogen levels; prolonged prothrombin time and partial thromboplastin time; decreased serum protein levels, especially albumin; hyponatremia and hypochloremia associated with increased aldosterone excretion; and abnormal hepatic function.
Mild mononuclear pleocytosis with slightly elevated protein content in cerebrospinal fluid is common.
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.
When walking in wooded or grassy areas, wear shoes, long pants tucked into socks and long-sleeved shirts. Try to stick to trails and avoid walking through low bushes and long grass.
Even if you've had Rocky Mountain spotted fever before, it can occur in the same person more than once. Follow precautions and check yourself for ticks.
Check yourself and your pets for ticks.
Remove a tick with tweezers.
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