Emerging human pathogen : identifying Spiroplasma ixodetis as a frequent cause of unlocalised febrile illness

Korva, Miša (author), Bogovič, Petra (author), Knap, Nataša (author), Kogoj, Rok (author), Slunečko, Jan (author), Zakotnik, Samo (author), Suljič, Alen (author), Resman Rus, Katarina (author), Pozvek, Patricija (author), Strle, Franc (author), Avšič-Županc, Tatjana (author), Petrovec, Miroslav (author)

Objectives: Febrile illness without clear localisation presents a significant diagnostic challenge due to nonspecific symptoms and diverse aetiologies. Spiroplasma ixodetis, an emerging tick-associated pathogen previously linked mainly to congenital cataracts, has not been well characterised in adults. We investigated the prevalence and clinical features of S. ixodetis infection in adults with acute febrile illness without localisation. Methods: Shotgun metagenomic sequencing identified S. ixodetis in the initial 209 patient cohort and the sequences were used to developed a novel real-time PCR assay targeting the 23S rRNA gene. Initial cohort screening was followed by testing 128 patients from an additionally selected targeted cohort. Positive results were confirmed by sequencing of 16S and 23S rRNA genes. Results: S. ixodetis DNA was confirmed in 7.2% patients from the initial and in 35.2% patients from the additional cohort (60 in total). All were identified in the period from April to October and 57% reported a recent tick-bite. Clinical presentation was homogenous, characterised by fever, headache, bicytopenia and liver enzyme abnormalities. Outcomes were favourable, with 15% requiring hospitalisation. Conclusion: This study identifies S. ixodetis as a previously unrecognised cause of adult febrile illness without localisation, bridging the gap between previously published data between tick studies and isolated human case reports.

• Language: English
• Keywords: 23S rRNA PCR, fever, metagenomics, patients, Spiroplasma ixodetis, tick-borne diseases
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 9 str.
• Numbering: Vol. 93, iss. 1, art. 106776
• PID: 20.500.12556/RUL-183193
• UDC: 616.9
• ISSN on article: 0163-4453
• DOI: 10.1016/j.jinf.2026.106776
• COBISS.SI-ID: 280582403
• Publication date in RUL: 07.06.2026

Record is a part of a journal

• Title: The Journal of infection
• Shortened title: J. infect.
• Publisher: Academic Press
• ISSN: 0163-4453
• COBISS.SI-ID: 6405383

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: 23S rRNA PCR, vročina, metagenomika, bolniki, Spiroplasma ixodetis, klopne bolezni