Rocky Mountain Spotted Fever

Incidence in USA: In most states, most commonly in the southeastern and south central states, there are ∼250-2200 cases per y.

Exposure to tick-infested terrain or dogs.

Severe infection; very young (<4 y), males and those with G6PD deficiency are at risk for death.

Mortality is 23% when untreated, 0.3–4.0% even with early treatment (within first 5 d).

Mortality increases with delay in Dx, older age (>60 y), male sex, very young age (<4 y), in blacks, chronic alcohol abuse, and those with G6PD deficiency.

Increased mortality secondary to CV instability and noncardiogenic pulm edema

Increased risk of organ injury due to compounded insults

Increased bleeding tendency

Severe intravascular volume depletion leading to shock

Lyte disturbances

Cardiac arrhythmias

Microvascular hemorrhage

Consumptive coagulopathy

Intraop respiratory and renal failure

Uncommon but severe; pathophysiology primarily due to endothelial cell prostaglandins, resulting in increased vascular permeability, edema, hypovolemia, and ischemia.

Initial symptoms appear in 1–3 d: Nonspecific, mimicking a viral syndrome with fever, headache, malaise, myalgias, arthralgias, and nausea; specific symptoms appear in 2–14 d, most in 5–7 d, mostly in the spring and summer months; pts generally have a known or possible tick bite.

Rash appears in most pts in 3–5 d, after onset of fever, initially maculopapular and progressing to petechiae; usually starts on the ankles and wrists, then palms and soles; finally spreads to the body and face; rash absent in 10–12%

Disease progression (more likely with delay in treatment) results in multiorgan involvement: Noncardiac pulm edema, encephalitis, myocarditis, hepatitis, bleeding (secondary to thrombocytopenia and direct vessel damage), and acute renal failure.

Rickettsia rickettsii is transmitted via the saliva of ticks after 6–10 h of attachment and feeding or by exposure to infected tick hemolymph during the removal of ticks.

Incubation period ∼7 d (2–14 d).

Obligatory intracellular bacterium that replicates in vascular endothelial cells, causing direct cell injury with loss of vascular integrity.