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Section 3. Summaries of Infectious Diseases
Rocky Mountain Spotted Fever
Clinical Manifestations
Etiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures
CLINICAL MANIFESTATIONS: Rocky Mountain spotted fever (RMSF)
is a systemic, small-vessel vasculitis with a characteristic
rash that usually occurs before the sixth day of illness. Fever,
myalgia, severe headache, nausea, vomiting, and anorexia are
major clinical features. Abdominal pain and diarrhea often are
present and can obscure the diagnosis. The rash initially is
erythematous and macular and later can become maculopapular
and often petechial. Rash usually appears first on the wrists
and ankles, often spreading within hours proximally to the trunk.
The palms and soles typically are involved. Although early development
of a rash is a useful diagnostic sign, rash fails to develop
in up to 20% of cases. Thrombocytopenia of varying severity
and hyponatremia develop in many cases. The white blood cell
count typically is normal, but leukopenia and anemia can occur.
The illness can last as long as 3 weeks and can be severe, with
prominent central nervous system, cardiac, pulmonary, gastrointestinal
tract, and renal involvement; disseminated intravascular coagulation;
and shock leading to death. Significant long-term sequelae are
common in patients with severe RMSF, including neurologic (paraparesis;
hearing loss; peripheral neuropathy; bladder and bowel incontinence;
and cerebellar, vestibular, and motor dysfunction) and nonneurologic
effects (disability from limb amputation).
ETIOLOGY: Rickettsia rickettsii is an obligate intracellular
pathogen and a member of the spotted fever group of rickettsiae.
The primary targets of infection in mammalian hosts are endothelial
cells lining the small vessels of all major tissues and organs.
EPIDEMIOLOGY: The disease is transmitted to humans by the bite
of an
Ixodes species tick. Many small wild animals and dogs
have antibodies to
R rickettsii, but their role as natural reservoirs
is not clear. Ticks are
. . . [Go to Full Text]
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