Current situation and emerging foot-and-mouth disease virus lineages in Egypt: Historicment SAT1 Introduction, and Vaccine Policy Implications.

Foot-and-mouth disease (FMD) continues to impose significant constraints on livestock health and productivity in Egypt due to the persistent circulation, evolution, and transboundary introduction of antigenically diverse foot-and-mouth disease virus (FMDV) serotypes and lineages. Since the 1950s, Egypt has experienced recurrent incursions of serotypes O, A, and SAT2, accompanied by progressive antigenic shifts, including the emergence of O/EA-3, A/Africa G-IV, and SAT2 Lib-12. Recent developments have further reshaped the national epidemiological landscape. In 2022, the detection of FMDV-A-Egy-AHRI-RL385-Ven-2022, phylogenetically linked to the EURO-SA lineage, provided the first evidence of intercontinental viral introduction into Egypt. This was followed in 2025 by the first confirmed incursion of serotype SAT1 (topotype I), previously absent from Egypt and its vaccine formulations. The introduction of SAT1 into a fully naïve livestock population triggered rapid viral spread and revealed a critical immunological gap associated with longstanding trivalent vaccination strategies. Vaccine-matching analyses conducted at the Central Laboratory for Evaluation of Veterinary Biologics revealed that ongoing antigenic drift, particularly within serotypes A and SAT2, had diminished the protective capacity of traditional vaccines. In response, vaccine formulations were updated to incorporate A EURO-SA, A Africa G-IV, and SAT2 Lib-12, and a monovalent SAT1 vaccine was developed for emergency deployment. This review integrates historical, molecular, antigenic, and epidemiological evidence to assess recent FMDV evolution in Egypt and its implications for vaccination policy. The findings highlight the urgent need for adaptive FMD control strategies that combine continuous genomic surveillance, systematic vaccine matching, and dynamic antigen updating to protect Egypt's livestock sector against an increasingly complex and evolving viral threat.