Other Spotted Fever Rickettsioses
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, 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 Spp). 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. Ixodid ticks and wild animals maintain the rickettsiae 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.
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 wk.
Complications and death are rare except among elderly or debilitated patients. However, the disease should not be ignored; a fulminant form of vasculitis can occur.
For details on diagnosis, see Overview of Rickettsial and Related Infections : Diagnosis.
Treatment of spotted fever rickettsioses is one of the following:
Measures can be taken to prevent tick bites (see Tick Bite Prevention).