Various rickettsiae transmitted by ixodid ticks cause spotted fever rickettsioses similar to but milder than Rocky Mountain spotted fever. Symptoms are an initial skin lesion, satellite adenopathy, and an erythematous maculopapular rash.
(See also Overview of Rickettsial and Related Infections.)
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 Diseases Caused by Rickettsia, Orientia, Ehrlichia, Anaplasma, and Coxiella Species). 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 (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 fourth 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 second week.
Complications and death are rare except among older patients or patients who are debilitated. However, the disease should not be ignored; a fulminant form of vasculitis can occur.
Diagnosis of Spotted Fever Rickettsioses
History and physical examination
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)
For details, see Diagnosis of Rickettsial and Related Infections.
Treatment of Spotted Fever Rickettsioses
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.)
Deer ticks
Preventing tick access to skin includes
Staying on paths and trails
Tucking trousers into boots or socks
Wearing long-sleeved shirts
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.
