ABSTRACT & COMMENTARY

Synopsis: It is the most commonly imported rickettsiosis in North America, and the increased frequency of travel to endemic areas may result in an increase in imported cases.

Source: Palau LA, Pankey GA. J Travel Med 1997;4: 179-182.
The authors describe a case of imported infection due to Mediterranean Spotted Fever (MSF) in a 56-year-old female physician returning to the United States from a three-week safari in Africa. She first traveled to Harare, Zimbabwe, and then spent several weeks travelling in the bush and canoeing in the Zambesi River between Zimbabwe and Zambia. She initially took doxycycline for malaria prophylaxis, but discontinued it after the first three days due to side effects. Although she did not recall a tick bite, she noticed fever, chills, and malaise within two weeks of arrival. Three days later, she developed a maculopapular rash which did not involve the palms and soles. Malaria was excluded, and she received empiric doxycycline with some symptomatic improvement. Upon return to the United States two days later, she had evidence of a tache noire on her abdomen and some residual rash. Serological studies were consistent with infection due toRickettsia conorii.

COMMENT BY CAROL A. KEMPER, MD

Disease caused by infection withR. conoriigoes by a variety of sobriquets including tick typhus, Mediterranean Spotted Fever, South African tick typhus, Kenya tick-bite fever, India tick typhus, and boutonneuse fever. This, in part, reflects the widespread geographic distribution of this organism, including southern Europe and other countries of the Mediterranean basin, the Black and Caspian Sea Basins, Israel, Turkey, India, Burma, West Pakistan, and Africa. Three-fourths of imported cases in North America are documented in travelers from Africa, and the remainder are from the Mediterranean. Serologic analyses indicate that exposure toR. conoriiis common in endemic areas, occurring in 11-26% of the general population in southern Europe and Israel, and in more than 80% of the dogs in southern France.

Although Palau and Pankey state that fewer than 50 imported cases of MSF into the United States have been confirmed by the Centers for Disease Control and Prevention, it is the most commonly imported rickettsiosis in North America, and the increased frequency of travel to endemic areas may result in an increase in imported cases. Physicians should, therefore, be prepared to include R. conorii infection in the differential diagnosis of maculopapular rash in patients with an appropriate travel history.

During my fellowship, Dr. Deresinski and I had the opportunity to see an interesting case of MSF in a 63-year-old man returning from safari in the bushveld of South Africa (Kemper CA, et al. Clin Infect Dis 1992;15:591-594). During the last days of his trip, he traveled through Kruger National Park in an open land rover, but did not recall any tick bites or contact with dogs. Within four days of returning to the United States, he developed headache, anorexia, and malaise. Two days later, he developed fever and rash on his arms and back that quickly evolved to the palms. On examination, he had a classic tache noire on his lower left calf just above the stocking line, but his rash was somewhat atypical in that some of the lesions were maculopapular and some were papulovesicular and even papulopustular. A clinical diagnosis of tick-bite fever was made, and he received doxycycline with prompt resolution of his symptoms.

Epidemiologic considerations and the clinical presentation are both keys to the diagnosis of MSF. The incubation period is approximately six days (range, 1-16 days) with the abrupt onset of symptoms in about one-half of the patients. The characteristic painless eschar at the site of the original tick bite can be found in one-half to three-fourths of patients, although it may not be readily identified, and it is seldom, if ever, seen in patients from Israel (possibly the result of a variant strain of R. conorii in Israel).

Rash occurs within one to six days in more than two-thirds of patients; it quickly involves the palms and soles in ~80-90% of cases and the face and scalp in one-third. The rash is typically described as erythematous and maculopapular or papular, although some patients develop atypical cutaneous manifestations with petechial or purpuric lesions, maculoerythematous lesions resembling the exanthem of murine (endemic) typhus (whose geographic distribution overlaps that of tick typhus), and, rarely, vesicular or pustulovesicular lesions resembling the lesions of rickettsial pox. Infection without evidence of rash has also been documented. The rashes in both of these cases were, therefore, somewhat atypical; the case above did not involve the palms or soles, and our case had an unusual papulovesicular/pustular appearance.

Most infections are benign and self-limited, but severe life-threatening disease occurs in approximately 5% and fatalities have been reported in up to 2.5%. Treatment should be initiated as soon as the diagnosis is suspected prior to obtaining the results of serological studies. A two-week course of doxycycline is recommended, although a single day of treatment may be sufficient. Ciprofloxacin is an effective alternative. A rise in indirect immunofluorescence antibody titers supports the epidemiological identification of acute infection with R. conorii, but does not completely exclude the possibility of infection with another spotted fever group organism, such as R. akari, or the newly designated species, R. Africae.