Epidemiology and clinical management of Leishmania infantum, Dirofilaria immitis, and Dirofilaria repens infections in dogs in Ticino, Switzerland: A combined questionnaire-based and multicentric retrospective study

Climate change and increasing dog importation and travel may facilitate the emergence of canine vector-borne diseases in previously non-endemic regions. Competent vectors of Dirofilaria spp. are widespread in Switzerland, and phlebotomine sand flies have been repeatedly documented in Ticino, adjacent to highly endemic areas of canine leishmaniosis and dirofilariosis in Italy. This study provided insights into the epidemiology of Leishmania infantum and Dirofilaria spp. infections in dogs in Ticino, and evaluated current diagnostic, management, and prevention practices. A multi-stakeholder approach was applied, combining structured interviews with animal shelter representatives, standardized online questionnaires for veterinarians and dog owners, along with a 25-year retrospective review of clinical records. Data comprised responses from 3/4 public shelters, 44/56 veterinarians, 8 dog owners, and 106 clinical records (91 L. infantum, 15 D. immitis). Leishmania infantum infections were reported by 2/3 shelters and 36/44 (81.8%) veterinarians within the year preceding data collection. Dirofilaria immitis infections were less frequent (1/3 shelters; 8/44 (18.2%) veterinarians); Dirofilaria repens was not reported. Most infected dogs originated from Italy; one D. immitis positive dog had no history of travel abroad. Veterinarians frequently reported asymptomatic L. infantum infections. Preventive recommendations were generally appropriate, but owner compliance was inconsistent. Retrospective analysis revealed incomplete diagnostic staging of dogs with L. infantum infection (retrospective LeishVet classification achievable in one-third of cases, primarily due to omitted urinalysis). The high number of - often asymptomatic - infected dogs and gaps in testing and vector prophylaxis, indicates a risk of endemic establishment of L. infantum and sustained transmission of Dirofilaria spp. in southern Switzerland.