Reports of Lipoptena fortisetosa on dogs and in the environment, and evidence of its widespread establishment in Hungary.

Lipoptena fortisetosa is a louse fly of East Asian origin that is considered a potential vector of several pathogenic bacteria and is most commonly associated with deer (Cervidae). The species has been detected in multiple countries in Europe; however, its exact distribution range is unknown. A single individual was detected on a dog at a veterinary clinic in Budapest, Hungary, where the presence of this species had not been confirmed previously. After acquiring information regarding the recent whereabouts of the dog, targeted louse fly collection with insect nets was performed in a forest in Central Transdanubia. Of the 30 flying, unfed specimens of Lipoptena spp., 23 were morphologically identified as L. fortisetosa. Following this, louse fly collections have been conducted across Hungary during the fall of 2025, including the collection of two additional specimens from a dog. According to these results, L. fortisetosa is established in several regions of the country, and this parasite can be effectively transported by dogs. The molecular analyses further confirmed the results, and the distinction between L. fortisetosa and Lipoptena cervi. The findings draw attention to the potential medical and veterinary significance of the emergence of novel vectors that may have been introduced through animal transport.