Merck Manual

Please confirm that you are a health care professional

Loading

Other Spotted Fever Rickettsioses

By

William A. Petri, Jr

, MD, PhD, University of Virginia School of Medicine

Last full review/revision Jul 2020| Content last modified Jul 2020
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Topic Resources

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.

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. 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.

Symptoms and Signs

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

  • Clinical features

  • 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

  • Doxycycline

Treatment of spotted fever rickettsioses is doxycycline 100 mg orally twice a day in adults for 5 days.

Prevention

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 and dog tick size comparison

Deer and dog tick size comparison

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.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version

Also of Interest

Videos

View All
Overview of Lyme Disease
Video
Overview of Lyme Disease
3D Models
View All
SARS-CoV-2
3D Model
SARS-CoV-2

SOCIAL MEDIA

TOP