Clinical and epidemiological features of cat-scratch disease: a 16-year case retrospective study in a portuguese tertiary care centre.

PURPOSE: Cat-scratch disease (CSD), primarily caused by Bartonella henselae, is a well-recognized zoonosis with a broad clinical spectrum, in which atypical manifestations may delay diagnosis. This study aimed to characterize the clinical and epidemiological profile of CSD at a Portuguese tertiary care centre and to evaluate the role of molecular and serological methods as complementary tools. METHODS: We conducted a retrospective cohort study including all patients with laboratory-confirmed CSD diagnosed at Unidade Local de Saúde de São João, Porto, between 2010 and 2025. PCR-positive specimens were further characterized by sequencing for Bartonella species identification. Comparative analyses were performed according to clinical presentation (typical versus systemic disease). RESULTS: Thirty-nine patients were included (median age 15 years), of whom 53.8% were paediatric. Cat exposure was reported in 94.9% of cases. Information regarding flea infestation and preventive measures in companion animals was unavailable. Systemic presentations occurred in 43.6% (17/39) of patients, most of whom (94.1%, 16/17) were immunocompetent. Among PCR-positive specimens successfully characterized by sequencing, all were identified as B. henselae. PCR positivity was higher in lymph node tissue than in blood specimens (79.2% vs. 15.8%). The median time from symptom onset to diagnosis was 52.5 days. At the time of diagnosis, serology was positive for IgG antibodies in 76.0% and IgM in 28.0% of CSD patients. Azithromycin monotherapy was most frequently used for typical disease (81.8%), whereas combination therapy was more commonly used in systemic cases (76.5%). Clinical resolution after a single treatment course was achieved in 74.4% of patients. CONCLUSION: CSD frequently presented with systemic involvement, including in immunocompetent patients. The prolonged delay between symptom onset and diagnosis highlights the need for increased clinical awareness, and improved access to serological and molecular diagnostics. Given the high frequency of cat exposure among affected patients, One Health strategies focused on responsible pet ownership, regular flea control and veterinary follow-up, may contribute to reducing Bartonella transmission and the burden of CSD.