Molecular detection of Rickettsia helvetica in lesion and blood samples after tick bites in Serbia: two cases with One Health implications
Pavle Banović , Dragana Mijatović , Verica Simin , Ivana Bogdan , Dejan Jakimovski , Angelique Foucault-Simonin and Alejandro Cabezas-Cruz
Researchers detected Rickettsia helvetica DNA in clinical samples from two patients after tick bites in Serbia, supporting lesion-focused molecular diagnostics and integrated One Health surveillance.
A new scientific article developed under the umbrella of the Balkan Association for Vector-Borne Diseases (BAVBD) has reported the molecular detection of Rickettsia helvetica in clinical samples collected from two patients following tick bites in Serbia.The Short Communication, entitled “Molecular detection of Rickettsia helvetica in lesion and blood samples after tick bites in Serbia: two cases with One Health implications,” has been accepted for publication in Diagnostic Microbiology & Infectious Disease. The collaboration brought together researchers affiliated with the BAVBD Diagnostics and Laboratory Research Task Force, the BAVBD Branch in Skopje, the Pasteur Institute Novi Sad, the University of Novi Sad, the University Clinic for Infectious Diseases and Febrile Conditions in Skopje, and ANSES–INRAE–École Nationale Vétérinaire d’Alfort in France.
Two tick-bite-associated cases
The first case involved a 65-year-old woman who developed two persistent, pruritic skin lesions after tick exposure in the Valjevo area. One of the removed ticks was identified as an adult female Ixodes ricinus. Molecular testing detected Rickettsia DNA in capillary blood collected directly from both skin lesions, and sequencing identified the organism as R. helvetica. Importantly, the patient’s whole-blood sample was PCR-negative, while serological testing did not demonstrate reproducible seroconversion.The second case involved an 8-year-old girl who developed a scalp papule and crust, followed by occipital and cervical lymph-node enlargement, after the attachment of an adult female Haemaphysalis punctata acquired in Petrovaradin Forest. The clinical presentation resembled SENLAT—scalp eschar and neck lymphadenopathy after a tick bite. In this case, R. helvetica DNA was identified by PCR and sequencing in both lesion-derived capillary blood and whole blood. The lesion and lymphadenopathy subsequently regressed following doxycycline treatment.The authors appropriately describe this presentation as “SENLAT-like.” Although R. helvetica was detected in the patient’s clinical samples, the findings do not establish it as a typical cause of SENLAT, which is more commonly associated with other Rickettsia species and Dermacentor ticks.
Why lesion-focused testing matters
One of the study’s most important practical messages concerns diagnostic sampling.Spotted fever group rickettsiae may be concentrated in endothelial tissue and cutaneous lesions rather than continuously circulating in peripheral blood. Whole-blood PCR can therefore produce a negative result despite the presence of rickettsial DNA at the tick-bite site. Serology may also be negative during early infection, and antimicrobial treatment can potentially attenuate or delay the antibody response.The detection of R. helvetica DNA in both lesions of the first patient—despite a negative whole-blood PCR result—illustrates why molecular testing of material obtained directly from a suspicious tick-bite lesion may provide important complementary diagnostic information.These findings support the development and evaluation of lesion-focused sampling approaches, particularly when patients present with persistent erythema, a papule, crust or eschar after a tick bite.
A One Health surveillance priority
The study also demonstrates the value of connecting clinical observations with information about tick vectors and exposure environments. The reported exposures involved both rural and peri-urban locations, including the Valjevo area and Petrovaradin Forest.Previous studies have demonstrated the circulation of R. helvetica in ticks in Serbia. However, the ticks removed in the two newly reported cases were not tested for rickettsiae. The authors therefore caution that direct transmission by the identified ticks cannot be conclusively established and that unrecognized exposure to another tick cannot be entirely excluded.Future surveillance should combine the testing of human clinical samples with analyses of removed ticks, questing ticks from suspected exposure locations, domestic animals and environmental conditions. Such integrated surveillance could improve understanding of the distribution, vectors and clinical importance of underdiagnosed spotted fever group rickettsioses in Serbia and the wider Balkan region.This publication reflects BAVBD’s commitment to connecting clinical medicine, laboratory diagnostics, vector research and epidemiological surveillance through regional and international One Health collaboration.
The open-access article is available at:https://doi.org/10.1016/j.diagmicrobio.2026.117571