(See also Overview of Rickettsial and Related Infections Overview of Rickettsial and Related Infections Rickettsial diseases (rickettsioses) and related diseases (anaplasmosis, ehrlichiosis, Q fever, scrub typhus) are caused by a group of gram-negative, obligately intracellular coccobacilli. All... read more .)
Spotted fever rickettsioses include North Asian tick-borne rickettsiosis, Queensland tick typhus, African tick typhus (African tick bite fever), Mediterranean spotted fever (boutonneuse fever), and Rickettsia parkeri rickettsiosis (transmitted by the Gulf Coast tick [Amblyomma maculatum]—see table). The causative agents belong to the spotted fever group of rickettsiae.
The epidemiology of these tick-borne rickettsioses resembles that of Rocky Mountain spotted fever Rocky Mountain Spotted Fever (RMSF) Rocky Mountain spotted fever (RMSF) is caused by Rickettsia rickettsii and transmitted by ixodid ticks. Symptoms are high fever, severe headache, and rash. (See also Overview of Rickettsial... read more (RMSF) in the Western Hemisphere. The arthropod vectors, with or without animal reservoirs, maintain these spotted fever rickettsia in nature. If humans intrude accidentally into the cycle, they become infected. In certain areas, the cycle of boutonneuse fever involves domiciliary environments, with the brown dog tick, Rhipicephalus sanguineus, as the dominant vector.
Symptoms and Signs of Spotted Fever Rickettsioses
The symptoms and signs are similar for all spotted fever rickettsioses and generally milder than with RMSF.
After an incubation period of 5 to 7 days, fever, malaise, headache, and conjunctival injection develop. With the onset of fever, a small buttonlike ulcer 2 to 5 mm in diameter with a black center appears (an eschar or, in boutonneuse fever, tache noire). Usually, the regional or satellite lymph nodes are enlarged. On about the 4th day of fever, a red maculopapular rash appears on the forearms and extends to most of the body, including the palms and soles. Fever lasts into the 2nd week.
Complications and death are rare except among older or debilitated patients. However, the disease should not be ignored; a fulminant form of vasculitis can occur.
Diagnosis of Spotted Fever Rickettsioses
Biopsy of rash with fluorescent antibody staining to detect organisms
Acute and convalescent serologic testing (serologic testing is not useful acutely)
Polymerase chain reaction (PCR)
Treatment of Spotted Fever Rickettsioses
Treatment of spotted fever rickettsioses is doxycycline 100 mg orally twice a day in adults for 5 days.
Prevention of Spotted Fever Rickettsioses
No effective vaccine is available to prevent spotted fever rickettsioses. Measures can be taken to prevent tick bites. (See also Centers for Disease Control and Prevention: Preventing tick bites.)
Preventing tick access to skin includes
Staying on paths and trails
Tucking trousers into boots or socks
Wearing long-sleeved shirts
Applying repellents with diethyltoluamide (DEET) to skin surfaces
DEET should be used cautiously in very young children because toxic reactions have been reported. Permethrin on clothing effectively kills ticks. Frequent searches for ticks, particularly in hairy areas and on children, are essential in endemic areas.
Engorged ticks should be removed with care and not crushed between the fingers because crushing the tick may result in disease transmission. The tick’s body should not be grasped or squeezed. Gradual traction on the head with a small forceps dislodges the tick. The point of attachment should be swabbed with alcohol. Petroleum jelly, lit matches, and other irritants are not effective ways to remove ticks and should not be used.
No practical means are available to rid entire areas of ticks, but tick populations may be reduced in endemic areas by controlling small-animal populations.
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