Molecular Detection of Bartonella henselae in Healthy Cats from Portugal (2015–2025): One Health Context and Implications for Transfusion Medicine

<i>Bartonella henselae</i> is a flea-borne zoonotic bacterium for which domestic cats constitute the principal reservoir. However, contemporary molecular epidemiological data from Portugal remain scarce. This retrospective laboratory study analysed EDTA-stabilised blood samples from apparently healthy cats submitted for routine screening by 74 veterinary centres across mainland Portugal and autonomous regions over an 11-year period (2015-2025). DNA extracts were tested using a species-specific TaqMan qPCR assay for <i>B. henselae</i> with an internal extraction control, and a subset of samples was subsequently confirmed by nested PCR followed by Sanger sequencing (<i>ribC</i>). Among 270 cats, 47 tested positive, yielding a qPCR prevalence of 17.4% (95% confidence interval [CI] 13.1-22.5). Submissions were predominantly from Northern Portugal, and infection status was not statistically associated with the Nomenclature of Territorial Units for Statistics (NUTS) level 2 region (<i>p</i> = 0.478). Infection was more frequent in younger cats (median age 2 years, interquartile range [IQR] 1-5; <i>p</i> = 0.037), while sex (<i>p</i> = 0.103) and breed (<i>p</i> = 0.730) were not significantly associated with infection status. These findings support endemic circulation of <i>B. henselae</i> in Portuguese cats at levels comparable to other temperate European regions. The detection of subclinical infection in apparently healthy cats is relevant to transfusion medicine and supports the inclusion of <i>B. henselae</i> qPCR screening in donor selection protocols.