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Rocky Mountain Spotted Fever Rocky Mountain Spotted Fever: First recognized in 1896 in the Snake River Valley of Idaho and was originally called "black measles" because of the characteristic rash. Howard T. Ricketts established the identity of the infectious organism that causes this disease, Rickettsia rickettsii. He and others described the epidemiologic features of the disease, including the role of tick vectors. Sadly, Dr. Ricketts died of typhus (another rickettsial disease) in Mexico in 1910. Epidemiology: A bit of a misnomer, this disease has been identified in almost all of the continental US, with perhaps the exception of Maine and Vermont Most cases reported in south Atlantic, southeastern and south central states 54% of cases were from NC, TN, OK, SC and Ark Transmission: Vector=tick Wood tick, dog tick and Lone Star tick Both dog and Lone Star ticks are found in NC Wood tick is primarily in western US, and Rocky Mountain area DOG TICK: Transmits RMSF, but probably not Lyme LONE-STAR TICK: Transmits RMSF, and human monocytic ehrlichiosis Two-thirds of RMSF cases occur in children younger than 15 years Males are infected more commonly (1.7-2.2:1) Caucasians are more common than AfricanAmericans Peak months of infection are April-October R. rickettsii organisms are released through saliva during a feeding Usually 12-24 hrs of attachment is required Incubation period is 2-14 days Once organisms enter the body, they multiply within endothelial cell linings of small blood vessels Signs and Symptoms: EARLY: LATE: Fever, nausea, vomiting, severe headache, anorexia and malaise Rash, joint pain and diarrhea Classic triad=fever, rash and headache Rash: appears between day 2 to 5 of illness Blanching, erythematous macules arouond ankles feet, later wrists and hands; palms and soles often involved Petechiae on day 6 10-15% of infected patients are without rash Important points: Only 40-60% of those infected have a history of tick bite RMSF may be clinically indisginguishable from Human Monocytic ehrlichiosis Laboratory tests: Hyponatremia (20%) Thrombocytopenia (33%) Anemia, increased LFTs or BUN (25%) CSF: monocytic pleocytosis, increased protein Diagnosis: Largely clinical Suspect if classic triad Acute and convalescent titers (> 3 wks apart) Immunofluorescence assay PCR Isolation of R rickettsii from clinical specimen Treatment: Should be started immediately Doxycycline, usually 7-10 days 100 mg PO BID for adults 4 mg/kg/day div BID for children Discontinue 72 hrs after defervescence Teeth staining if < 9 years old; probably requires 5-6 courses before staining appears Prevention: Protective clothing Repellants Avoid DEET if under 12 months Full body examinations To remove attached ticks, use the following procedure: 1. Use fine-tipped tweezers or shield your fingers with a tissue, paper towel, or rubber gloves (Figure 17). When possible, persons should avoid removing ticks with bare hands. 2. Grasp the tick as close to the skin surface as possible and pull upward with steady, even pressure (Figure 18). Do not twist or jerk the tick; this may cause the mouthparts to break off and remain in the skin. (If this happens, remove mouthparts with tweezers. Consult your health care provider if infection occurs.) 3. Do not squeeze, crush, or puncture the body of the tick because its fluids (saliva, body fluids, gut contents) may contain infectious organisms. 4. After removing the tick, thoroughly disinfect the bite site and wash your hands with soap and water. 5. Save the tick for identification in case you become ill. This may help your doctor make an accurate diagnosis. Place the tick in a plastic bag and put it in your freezer. Write the date of the bite on a piece of paper with a pencil and place it in the bag. Resources: Center for Disease Control and Prevention. Rocky Mountain spotted fever. Available at: http://www.cdc.gov/ncidod/dvrd/rmsf Pickering, L. Red Book; 26th edition. pp. 532534. Razzaq, S. Rocky Mountain Spotted Fever: A Physician’s Challenge. Pediatrics in Review. Vol. 26, No. 4 April 2005. pp. 125-129.