Disease/Syndrome

Rocky Mountain spotted fever

Category

Infection, Occupational

Acute/Chronic

Acute-Severe

Synonyms

North American tick typhus; New World spotted fever; Tickborne typhus fever; Sao Paulo fever; Rickettsia rickettsii infection

Biomedical References

Search PubMed

Comments

INITIAL SYMPTOMS: Fever, headache, myalgia with maculopapular rash on the 3rd and 5th days (in the season and locality of tick activity); [CCDM] FINDINGS: The rash includes the palms and soles in about 30% of cases and spreads to the trunk. Patients develop a petechial rash on or after the sixth day. Petechiae are associated with end organ damage. [CCDM, p. 515] Common findings after the initial flu-like syndrome include conjunctival injection, stiff neck, nausea/vomiting, abdominal pain, hepatomegaly, splenomegaly, and hypotension. Pneumonitis (cough, rales, and pulmonary infiltrates) occurs in about 17% to 30% of patients. Encephalitis with confusion, lethargy, and delirium occur in over 25% of patients. Patients may also have ataxia, seizures, and coma. The CSF shows evidence of meningitis. Severe hemorrhage occurs "very infrequently." Laboratory abnormalities include abnormal liver and kidney function tests, hyponatremia (56% to 91% of patients), proteinuria, microscopic hematuria, mild thrombocytopenia, and increased bands (immature neutrophils). Over 30% of patients have elevated bilirubin levels, and jaundice is a sign of fulminant disease. Acute renal failure following hypotension is also common. Myocarditis is a rare complication. [ID, p. 1473-80] R. rickettsia targets the vascular endothelial cells resulting in edema, hypovolemia, ischemia, and tissue injury. Retinal vein engorgement, flame hemorrhages, and papilledema (normal CSF pressure) are seen in some cases. Rhabdomyolysis has been reported occasionally. [Harrison ID, p. 731] Chest x-ray findings include infiltrates and pleural effusions. Other findings are lymphadenopathy (27%), diarrhea, (20%), and anemia (5%-24%). Leukopenia, thrombocytopenia, and elevated liver enzymes are common. In 1/3 of cases, CSF shows increased leukocytes with a predominance of either lymphocytes or neutrophils. G6PD deficiency is a risk factor for hemolytic anemia and fulminant disease. In a series of pediatric cases, 15% of survivors had neurological deficits at discharge with encephalopathy, ataxia, and blindness. [PPID, p. 2200-2] EPIDEMIOLOGY: Tick bites are typically painless and often not recognized. Cases have been reported from breaks in the skin contaminated by crushed ticks or tick feces. The natural animal reservoirs are ticks. Dogs, rodents, and other animals may become infected. [CCDM] Goats, sheep, and rabbits are also reservoirs. [PPID 7th Ed., p. 4002] Fatality rates without treatment: Rocky Mountain (20-25%); [Cohen, p. 1808]

Latency/Incubation

2-14 days with a median of 7 days; [PPID, p. 2200]

Diagnostic

Paired sera; Skin biopsy (immunostain or PCR); [CCDM] DFA of skin biopsy S/S of about 70%/100%; IgM appears by day 3-8, peaks at 1 mo., & lasts 3-4 mo.; [Wallach, p. 553] DFA skin biopsy rapid & may be available in hospital; Paired sera (IFA); [ABX Guide]

ICD-9 Code

082.0

Effective Antimicrobics

Yes

Reference Link

CDC - Rocky mountain spotted fever

Image

CDC: RMSF

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