A Review of Molecular and Immunological Dynamics of Bovine Brucellosis: Reproductive Pathogenesis, Diagnostic Challenges, and Strategic Use of S۱۹ Vaccine in Emergency Contexts

Bovine brucellosis, primarily caused by Brucella abortus, remains a major reproductive and economic challenge in cattle production systems worldwide. The disease is characterized by late-term abortion, retained placenta, infertility, and reduced milk yield, resulting from the bacterium's ability to establish chronic intracellular infection and preferentially localize in the gravid uterus. The interaction between bacterial virulence factors and host immune modulation plays a central role in placental inflammation, fetal loss, and persistent infection. Despite decades of control efforts, brucellosis continues to persist in endemic regions, particularly where test-and-slaughter programs are economically or logistically impractical. In such settings, vaccination remains the cornerstone of disease control. The live attenuated strain ۱۹ (S۱۹) vaccine has historically demonstrated high efficacy in reducing abortion rates and transmission; however, its use is associated with diagnostic interference, residual virulence concerns, and complex decision-making during outbreak situations. Emergency vaccination strategies, although capable of rapidly stabilizing herd-level reproductive performance, may introduce serological ambiguity and complicate surveillance programs. This review provides a comprehensive analysis of the molecular pathogenesis of bovine brucellosis, its reproductive consequences, diagnostic limitations, and the immunological basis of protection induced by S۱۹ vaccination. Particular emphasis is placed on the strategic application of emergency vaccination within integrated epidemiological frameworks. Understanding the balance between individual immune protection and population-level disease control is essential for designing sustainable brucellosis management programs in endemic regions.

کلیدواژه ها:

Bovine brucellosis ، Brucella abortus ، Reproductive failure ، S۱۹ vaccine ، Emergency vaccination ، Intracellular pathogenesis ، Herd immunity ، Diagnostic interference ، Veterinary epidemiology