Laboratory diagnosis and biosecurity of selected equine viral infections in breeding populations

Viral infections represent a persistent health and economic challenge in equine breeding populations because of their impact on reproductive efficiency, respiratory health, neurological disorders, and the overall stability of breeding operations. This review examines selected viral pathogens of relevance in breeding horses, with particular focus on infections that represent diagnostic and biosecurity challenges: equine herpesviruses 1 and 4, equine arteritis virus, equine influenza virus, and West Nile virus as a regionally relevant vector-borne agent. This review further highlights the characteristics of breeding practices that facilitate virus introduction, maintenance, and transmission, including animal movement, seasonal breeding patterns, intensive contact structures, and stressassociated reactivation of latent infections. Furthermore, the diagnostic value of different sample types and sampling strategies is discussed, as well as the benefits and limitations of molecular, virological, and serological methods in the investigation of respiratory, reproductive, and neurological diseases. Interpretation of laboratory findings within an appropriate clinical and epizootiological context is particularly emphasized, as test results alone may be insufficient for accurate assessment of infection status or herd-level risk. Additionally, this review discusses key biosecurity principles for prevention and control and outlines current challenges and future priorities for equine viral disease surveillance and management in Serbia. Effective control of equine viral infections in breeding populations requires the integration of timely laboratory diagnosis, structured surveillance, and consistently applied biosecurity measures.