Page 81 - Journal of Special Operations Medicine - Fall 2016

Take control An Ongoing Series

of the risk of infection Rocky Mountain Spotted Fever

Mark W. Burnett, MD

INTRODUCTION the illness, and the rash may be faint or difficult to ap-
preciate in those with dark skin. A small percentage of
Rocky Mountain spotted fever (RMSF), one of the most patients may never develop an appreciable rash. Chil-
confusingly named of all infectious illnesses, is a tick- dren more often develop a rash, and do so earlier in the
borne rickettsial disease that has been reported across course of illness, than do adult patients.
most of the United States, as well as northern Mexico
and into South America. In fact, five eastern and central Left untreated or improperly treated, patients with
states (North Carolina, Tennessee, Missouri, Arkansas, RMSF may develop abdominal pain, thrombocytopenia,
and Oklahoma) account for almost two-thirds of all cutaneous necrosis, renal failure, and meningoencepha-
cases of RMSF in the United States.
litis. RMSF is the most commonly fatal rickettsial dis-
ease in the United States. The case fatality was a quarter
Caused by Rickettsia rickettsii, a bacterium in the order of all cases in the preantibiotic era, and still approaches
Rickettsiales, RMSF is transmitted to humans as inci- 10% today. Long-term problems of survivors of this dis-
dental hosts by the bite of several species of ticks. At ease include cognitive deficiencies, hearing loss, blind-
least four species of ticks have been shown to carry the ness, and cerebellar, vestibular, and motor disabilities.
disease in humans. Dermacentor variabilis, the Ameri-
can dog tick, is the most common culprit and has been
found in the eastern, central, and Pacific coastal regions Diagnosis
of the United States. The Rocky Mountain wood tick,
D. andersoni; the brown dog tick, Rhipicephalus san- The laboratory diagnosis of RMSF is confirmatory; con-
guineus; and a number of tick species of the genus Am- sideration of the disease process, and including it in the
blyomma have been shown to transmit the disease in the differential diagnosis is key. Paired acute and convales-
Forward western and southwestern regions of the United States, cent indirect immunofluorescence antibody assays are
Evacuation surgical with the range of the latter as far south as Argentina. the gold standard but are not sensitive in the first week
of the illness, and the convalescent sample may be af-
The range of this rickettsial disease is clearly not limited
Critical care Definitive to the Rocky Mountains. fected by the prompt initiation of appropriate antibiot-
ics. Testing for immunoglobulin IgM and IgG antibodies
transport care Clinical Presentation or detection of Rickettsia rickettsii by polymerase chain
reaction can be problematic because these results can be
Nonspecific symptoms, which may include a sudden on- difficult to interpret, and should be done in conjunction
Prolonged field care set of fever, headaches, chills, nausea, vomiting, myal- with an infectious disease specialist.
gia, and photophobia, develop anywhere between 3 and
12 days after the bite of an infected tick, or between the Thrombocytopenia, hepatic transaminase elevation,
fourth and eighth day after an attached tick is found. and hyponatremia in a febrile patient with or without a
The rash of RMSF appears 2–4 days after the onset of rash should raise the suspicion of a rickettsial infection,
fever. The rash is described initially as small (1–5mm) which, in the United States, must include consideration
pink macules on the wrists and ankles, which spread to of RMSF.
Your choice of wound dressings may help mitigate the palms, soles, arms, legs, and trunk. Over the next
several days the rash becomes petechial, eventually be-
the risk of a surgical site and soft tissue infection coming the classic generalized petechial rash that also Treatment
in all sites of care involves the palms and soles of the feet. Less than 50% The drug of choice for treatment of any tick-borne rick-
ettsial infection is doxycycline, including for infection in
of those infected exhibit the rash in the first 3 days of
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