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Key Diagnostic Tests.

The key physical finding is a rash beginning on the ankles and wrists accompanied by fever, headache and weakness.

• Immunofluorescent detection of the microorganism in biopsies
• Detection of antigens or antibody to the agent in the blood (serology)
• Weil-Felix test
• Thrombocytopenia and elevated white cell count in second week.

Differential Diagnosis Other disease or conditions that need to be eliminated
Other infectious diseases	Other problems
Dengue fever Lyme disease Measles Other rickettsial diseases	None
NOTE: Differential diagnosis of Rickettsial disease is difficult, but antibiotic treatments are generally effective against them and it is preferable to begin a general antibiotic treatment as soon as Rickettsial involvement is suspected than to wait for confirmation.
	A child's right hand showing a typical Rocky Mountain spotted fever rash. (Photograph courtesy of the Centers for Disease Control.)

Symptoms and effects.

After an incubation period of about 7 days (2-14 days), the victim develops a fever of 102-104°F (39-40°C), fever, headache, abdominal pain, joint pain, nausea and vomiting. The fever can last up to 20 days if not treated. Within a few days the tongue develops a thick white coating and a rash develops around the wrists and ankles that can spread to cover the entire body within a few days. The spots gradually become hard papules and may merge and slough off leaving brown discolored regions that may take weeks to heal. If untreated, the rash can become gangrenous. In serious cases the pulse can become rapid and feeble and blood pressure can drop to very low levels leading to shock, delirium, and peripheral cyanosis and gangrene. A cough may develop and the patient develops rapid shallow breathing although there may be some fluid in the lungs. Many organs, including the liver and kidneys can be affected, leading to a drop in the output of urine with the urine being dark and unusually high in albumin. Deafness is said to be "not uncommon." Death is rare (about 5% of cases) but there can be a vascular collapse.

Vaccination (Immunoprophylaxis)

A vaccine is not available

Antibiotics

The disease responds well to tetracyclines, which must be taken until three days after the fever subsides. Doxycycline is preferred.

Supportive care

Ticks must be removed. The disease can affect many organs, so a wide range of supportive measures, e.g. analgesics, maintenance of blood pressure, supporting of breathing, must be kept ready. Intravenous prednisolone and cold-sponging of patients with high fevers (>40°C, 104°F) are often used in the treatment of rickettsial disease.

Decontamination

The agent is killed by standard disinfectants (1% sodium hypochlorite, 70% ethanol, glutaraldehyde, formaldehyde) and to moist heat (121°C for at least 15 min) and dry heat (160-170°C for at least 1 hour).

Treat the affected area for tick infestation. The patient and his medical and nursing staff may also need to be treated with malathion or DDT to prevent reinfection.

Agent Properties and Potential Uses

The disease is specific to the Americas and is unknown and misdiagnosed in the rest of the world. R. ricketsii is not stable outside of its tick vector and could be dispersed by releasing infected ticks. The infective dose is very low at approximately 10 organisms.

Terrorist Acquisition and Attempted Use.

• None confirmed.