The increasing incidence and transmission of tickborne diseases is a major public health challenge. Although surveillance contributes to understanding the distribution and ecology of tickborne diseases, they remain underdiagnosed (1). Rickettsia massiliae, a spotted fever group Rickettsia species, is a human pathogen that was first isolated from Rhipicephalus spp. ticks in France in the 1990s (2). Since then, R. massiliae has been identified in questing and feeding ticks from a variety of animal hosts and in asymptomatic humans across regions of Europe, Africa, Asia, and limited areas of the Americas (3). R. massiliae was first recognized as a human pathogen in 2006 (4). Only 6 confirmed cases of R. massiliae caused rickettsiosis have been reported, highlighting its emergence as a tickborne rickettsial pathogen (5–7).

R. massiliae infection often causes clinical symptoms similar to other rickettsial infections, including fever, muscle pain, rash, hepatomegaly, scalp bedsores, neck lymphadenopathy, and eye issues such as retinal vasculitis, conjunctivitis, and vision loss (8). Although ticks of the genus Rhipicephalus are the primary vectors (9), the tick species responsible for the transmission of R. massiliae to humans has not been identified. We report a laboratory-confirmed case of R. massiliae infection in a patient from southern Spain.

In January 2023, a pediatric patient was brought to medical care for a dark eschar on the right hemiscrotum, associated with pruritus, pain, and local inflammation. The patient reported travel 2 weeks before seeking medical attention to a periurban area of Granada Province, southern Spain, where he had contact with a domestic dog but no known arthropod exposure. He remained afebrile, except for a single temperature of 38°C on the day of admission. Laboratory test results were unremarkable, including a leukocyte count of 8.9 × 10³ cells/µL (68.4% neutrophils), platelet count of 266 × 10³/µL, and hemoglobin level of 13.9 g/dL. The C-reactive protein result was elevated (51.8 mg/L; reference range <5.0 mg/L). Scrotal ultrasonography revealed thickening of the tunica vaginalis with mild hyperemia, but the testes were unaffected. Serologic testing for Borrelia burgdorferi, Coxiella burnetii, and Rickettsia conorii yielded negative results. The patient was treated with intravenous amoxicillin/clavulanic acid (25 mg/kg/8 h for 3 d), leading to clinical improvement. Before he was discharged, a lesion scraping was collected for microbiological analysis. Patient follow-up was conducted at the Pediatric Infectious Diseases outpatient clinic (Granada, Spain); the patient was treated with oral amoxicillin/clavulanic acid (25 mg/kg/8 h for 1 wk). Twenty days after symptom onset and confirmed rickettsial infection, the patient was prescribed doxycycline (100 mg/12 h for 3 d), leading to complete resolution of symptoms and signs.

Biopsy material was submitted to the Special Pathogens Reference and Research Laboratory, National Center for Microbiology (Madrid, Spain) for the detection of tickborne pathogens. We extracted DNA from the biopsy sample by using the QIAamp Tissue Kit (QIAGEN, https://www.qiagen.com) according to the manufacturer’s instructions. We detected DNA from Rickettsia spp. by performing PCR amplification of fragments from the 23S–5S rRNA intergenic spacer and the outer membrane protein A (ompA) gene (10). We purified PCR amplicons and sequenced the amplicons bidirectionally by capillary electrophoresis by using BigDye Terminator chemistry on an ABI PRISM 3130 automated sequencer (Thermo Fisher Scientific, https://www.thermofisher.com).

We generated a consensus sequence for the 23S–5S rRNA intergenic spacer (GenBank accession no. PV679725) by aligning the sequence fragments to reference sequences retrieved from the GenBank database. We determined sequence similarity by using BLASTn (https://blast.ncbi.nlm.nih.gov). The sequence shared 100% identity with R. massiliae strain MTU5 (GenBank accession no. AY125013) and with an R. massiliae isolate (accession no. PP263054) detected in a tick belonging to the Rhipicephalus sanguineus complex from Spain. The consensus sequence also shared >99% identity with Rickettsia spp. isolated from ticks collected in Romania (accession no. MG450328) and Tunisia (accession no. KF245444) and the R. massiliae B29 strain isolated from Spain (accession no. AY125014).

We detected R. massiliae DNA from a skin biopsy of a patient with signs and symptoms consistent with rickettsial infection. The sequence we generated shared 99%–100% identity with R. massiliae strains previously isolated from ticks in other regions of Spain and Mediterranean countries. Our findings provide evidence that R. massiliae is an emerging cause of human rickettsiosis and highlight the diagnostic relevance of eschars in rickettsial infections. Eschars can be clinical indicators for early recognition, enabling prompt antimicrobial therapy, improving patient outcomes, and enhancing epidemiologic surveillance of emerging rickettsial infections.

The limited number of reported cases of R. massiliae in humans, despite the high prevalence in Rhipicephalus ticks, might reflect underdiagnosis because of nonspecific clinical signs and symptoms and limited molecular testing. Limited human–tick contact might also contribute to the lack of cases, because some Rhipicephalus species have limited anthropophilic behavior and exposure is likely concentrated in periurban settings. Because of the complexity of pathogen–vector–host interactions and the potential for severe clinical outcomes, R. massiliae should be considered an emerging public health concern in Mediterranean regions.

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