To the Editor: Tick-borne rickettsioses are zoonoses caused by spotted fever group
(SFG) Rickettsia spp (
1
), which have been reported as a frequent cause of fever in international travelers
(
2
). In Egypt, Mediterranean spotted fever caused by Rickettsia conorii transmitted
by the brown dog tick, Rhipicephalus sanguineus, is known to be present, although
cases are rarely documented. Moreover, an emerging pathogen, R. aeschlimannii, has
been detected in Hyalomma dromedarii ticks, collected from camels, and in H. impeltatum
and H. marginatum rufipes, collected from cows (
3
). We report a case of Rickettsia sibirica mongolitimonae infection in a French traveler
who returned from Egypt
In September 2009, a previously healthy 52-year-old man living in France was admitted
to the infectious diseases unit of a hospital in Nantes, France, with a 10-day history
of fever, asthenia, headache, and arthromyalgia. Three days earlier, he had returned
from a 2-week trip to Egypt. He had fever (38°C), painful axillary lymphadenopathies,
and an inoculation eschar surrounded by an inflammatory halo on the left scapular
area (Figure A1), but he did not have a rash. During his travel, he had been unsuccessfully
treated for headache, arthromyalgia, and diarrhea by amoxicillin-clavulanate (3 g/d),
nonsteroidal antiinflammatory drugs, and gentamicin cream on the eschar for 3 d. No
tick bite was reported by the patient. We suspected an SFG rickettsiosis. The patient
received 200 mg doxycycline in a single dose and rapidly improved.
The immunofluorescence assay for antibodies reactive against SFG antigens showed increased
levels of immunoglobulin M (titer 16) and G (titer 128). Results of Western blot with
cross-adsorption assays supported the hypothesis that the infection was caused by
R. sibirica mongolitimonae (
1
). To identify the involved rickettsiae, PCR amplifications and sequencing gltA, ompA,
and ompB fragment genes of Rickettsia spp. and multispacer typing (MST), based on
the sequence of variable intergenic spacers, were performed by using DNA samples obtained
from an eschar biopsy and a lesion swab (
4
,
5
). A negative control (sterile water and DNA from a sterile biopsy specimen) and a
positive control (DNA from R. montanensis) were included in each test. Amplicon sequencing
confirmed the presence of R. sibirica mongolitimonae DNA in patient samples. The sequence
homology to R. sibirica mongolitimonae DNA was ompA, 99.4%; gltA, 99.7%; and ompB,
100% (GenBank accession nos. DQ097082, DQ097081, and AF123715, respectively). The
MST sequences were 100% homologous to the genotype of R. sibirica mongolitimonae MST
type U (idem HA-91). We injected shell vial cultures with eschar biopsy specimens
(
4
). Fifteen days later, positive Gimenez staining and immunofluorescence confirmed
the presence of Rickettsia sp. in cell culture, and R. sibirica mongolitimonae was
identified by PCR and sequencing as described above (Figure A1).
R. sibirica mongolitimonae was first isolated in Beijing in 1991 from H. asiaticum
ticks (formerly named R. sibirica HA-91), and the first human infection was reported
in 1996 (
4
). Since that time, R. sibirica mongolitimonae infections have been diagnosed in 15
additional patients: 12 from Europe (France, Portugal, Greece, and Spain) and 3 from
Africa (Algeria, South Africa, and the present patient who returned from Egypt). The
application of genotypic criteria to R. sibirica mongolitimonae classified the organism
as a subspecies of R. sibirica group, in spite of its distinct serotypes and specific
epidemiologic features compared to R. sibirica sibirica, the causative agent of Siberian
tick typhus or North Asian tick typhus (
1
).
R. sibirica mongolitimonae causes lymphangitis-associated rickettsiosis. The available
clinical features for the only 16 reported cases (10 men, 6 women) include fever in
all patients (range 38˚C–39.5°C), chills (3/16 patients), headache (13/16), myalgia
(13/16), arthralgia (3/16), cutaneous rash (11/16), enlarged lymph nodes (10/16),
lymphangitis expanding from an inoculation eschar to the draining node (6/16), and
retinal vasculitis in a pregnant woman (
6
,
7
). Two patients exhibited 2 eschars. Most eschars were on the legs, but some patients
had an eschar on the back, the abdomen, the arm, or the face. The patients’ median
age was 50 years (range 20–76 years). A tick bite or tick handling was reported for
5 patients, but no tick was collected for further examination. In France, 7 patients
probably came in contact with R. sibirica mongolitimonae–infected ticks in their gardens,
and 2 other patients were probably exposed during a walk in the Camargue National
Park, where migratory birds are frequently present (
7
). Infection with R. sibirica mongolitimonae occurred primarily between March and
September. A single case was reported in December in Greece. R. sibirica mongolitimonae
has been detected in several Hyalomma spp. ticks in Niger, Greece, the People’s Republic
of China, Senegal, and in Rh. pusillus ticks in Portugal (
6
–
8
). Although Hyalomma spp. ticks seem to be associated with R. sibirica mongolitimonae,
more experimental data are needed to determine the tick vectors and reservoirs of
this rickettsia.
Clinicians in Egypt and those who may see patients returning from this country should
be aware that several species of rickettsiae are found in this region. Thus, they
should consider a range of SFG rickettsial diseases in the differential diagnosis
of patients with febrile illnesses.