Feline leukaemia virus (FeLV) is a retrovirus associated with fatal disease in progressively infected cats. While testing/removal and vaccination led to a decreased prevalence of FeLV, recently, this decrease has reportedly stagnated in some countries. This study aimed to prospectively determine the prevalence of FeLV viraemia in cats taken to veterinary facilities in 32 European countries. FeLV viral RNA was semiquantitatively detected in saliva, using RT-qPCR as a measure of viraemia. Risk and protective factors were assessed using an online questionnaire to report geographic, demographic, husbandry, FeLV vaccination, and clinical data. The overall prevalence of FeLV viraemia in cats visiting a veterinary facility, of which 10.4% were shelter and rescue cats, was 2.3% (141/6005; 95% CI: 2.0%-2.8%) with the highest prevalences in Portugal, Hungary, and Italy/Malta (5.7%-8.8%). Using multivariate analysis, seven risk factors (Southern Europe, male intact, 1-6 years of age, indoor and outdoor or outdoor-only living, living in a group of ≥5 cats, illness), and three protective factors (Northern Europe, Western Europe, pedigree cats) were identified. Using classification and regression tree (CART) analysis, the origin of cats in Europe, pedigree, and access to outdoors were important predictors of FeLV status. FeLV-infected sick cats shed more viral RNA than FeLV-infected healthy cats, and they suffered more frequently from anaemia, anorexia, and gingivitis/stomatitis than uninfected sick cats. Most cats had never been FeLV-vaccinated; vaccination rates were indirectly associated with the gross domestic product (GDP) per capita. In conclusion, we identified countries where FeLV was undetectable, demonstrating that the infection can be eradicated and highlighting those regions where awareness and prevention should be increased.

Bristol Veterinary School University of Bristol Bristol BS40 5DU UK and Chief Medical Officer Linnaeus Group Shirley Solihull B90 4BN UK

Bygholm Dyrehospital 8700 Horsens Denmark

CatVet Kissaklinikka 00400 Helsinki Finland

Clinic of Small Animal Medicine Centre for Clinical Veterinary Medicine LMU Munich 80539 Munich Germany

Clinical Laboratory Department of Clinical Diagnostics and Services and Center for Clinical Studies Vetsuisse Faculty University of Zurich 8057 Zurich Switzerland

Department of Animal Protection Welfare and Behavior Faculty of Veterinary Hygiene and Ecology University of Veterinary and Pharmaceutical Sciences Brno 612 42 Brno Czech Republic

Department of Geography University of Zurich 8057 Zurich Switzerland

Department of Infectious and Parasitic Diseases Research Unit of Epidemiology and Risk Analysis Applied to Veterinary Fundamental and Applied Research for Animal and Health Center Faculty of Veterinary Medicine University of Liège B 4000 Liège Belgium

Department of Small Animal Diseases with Clinic Faculty of Veterinary Medicine Warsaw University of Life Sciences SGGW 02 787 Warsaw Poland

Dipartimento di Scienze Veterinarie Università di Messina 98168 Messina Italy

Faculty of Veterinary Medicine Latvia University of Lifesciences and Technologies LV 3004 Jelgava Latvia

Faculty of Veterinary Medicine Università degli Studi di Teramo 64100 Teramo Italy

Fundació Hospital Clínic Veterinari Universitat Autònoma de Barcelona 08193 Bellaterra Barcelona Spain

Institute of Animal Hygiene and Veterinary Public Health University of Leipzig 04103 Leipzig Germany

Institute of Biology and Immunology of Reproduction 1113 Sofia Bulgaria

Institute of Virology Department for Pathobiology University of Veterinary Medicine 1210 Vienna Austria

Jakov Veterinary Centre Gerosios Vilties g 1 LT 03147 Vilnius Lithuania

Jamaren Swedish Veterinary Feline Study Group 275 71 Lövestad Sweden

Kleintierklinik BolligerTschuor AG Fachtierärzte für Kleintiere 4665 Oftringen Zofingen Switzerland

Loomakliinik 51014 Tartu Estonia

MRC University of Glasgow Centre for Virus Research Glasgow G61 1QH UK

Scanelis laboratory 31770 Colomiers France

School of Veterinary Medicine University College Dublin Belfield Dublin 4 Ireland

School of Veterinary Medicine University of Glasgow Glasgow G61 1QH UK

Slovak Small Animal Veterinary Association 821 02 Bratislava Slovakia

Small Animal Emergency Clinic 637 00 Brno Jundrov Czech Republic

Swedish University of Agricultural Sciences 750 07 Uppsala Sweden

Tierklinik Strebersdorf 1210 Vienna Austria

University of Utrecht Faculty of Veterinary Medicine Department of Infectious Diseases and Immunology 3584 CL Utrecht Netherlands

University of Veterinary Medicine 1078 Budapest Hungary

Vetalmada small animal clinic 2800 052 Almada Portugal

Veterinarska klinika Kreszinger 10360 Sesvete Zagreb Croatia

Veterinary Diagnostic Services School of Veterinary Medicine College of Medical Veterinary and Life Sciences University of Glasgow Glasgow G61 1QH UK

Veterinary Virology and Animal Viral Diseases Department of Infectious and Parasitic Diseases FARAH Research Centre Faculty of Veterinary Medicine Liège University B 4000 Liège Belgium

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