Recombinant Alphaherpesvirus Vectors in Veterinary Vaccinology: Platforms, Applications, and Translational Challenges

Animal infectious diseases impose severe economic burdens on livestock industries, threaten wildlife populations, and compromise food security. Although vaccination remains the cornerstone of disease prevention, conventional vaccine platforms are often constrained by safety, efficacy, or manufacturing scalability. This narrative review provides a comprehensive analysis of the state of the art in herpesvirus-vectored vaccines for veterinary applications, focusing on five well-characterized alphaherpesviruses: Bovine herpesvirus type 1 (BoHV-1), Pseudorabies virus (PRV), Marek's disease virus (MDV), Equine herpesvirus type 1 (EHV-1), and Duck enteritis virus (DEV). The intrinsic characteristics of herpesviruses, including large, stable genomes; the capacity for foreign gene insertion; broad host tropism; and the ability to elicit robust humoral and cellular immunity, are examined, and their performance is compared with that of traditional vaccine platforms. Key advances in vectored vaccine development are highlighted, from proof-of-concept studies to the creation of advanced multivalent constructs. These approaches demonstrate protective efficacy against a range of significant animal pathogens, including foot-and-mouth disease virus, porcine reproductive and respiratory syndrome virus, avian influenza virus, infectious bursal disease virus, and West Nile virus. The literature was identified through systematic searches of PubMed, Google Scholar, and Web of Science (1990-2026), followed by title/abstract screening and reference chaining. Future directions in vector engineering, mucosal delivery, and synthetic biology approaches are considered. Herpesvirus-vectored vaccines represent a versatile platform for enhancing animal health, supporting sustainable agriculture, and mitigating zoonotic risks.