Vaccination paradox in Bluetongue control: a review

The bluetongue virus (BTV) is the causative agent of bluetongue, a non-contagious viral disease that affects ruminants. It is transmitted by insects of the Culicoides genus. The disease's complexity is reflected in the large number of recognized serotypes. This disease can be particularly severe in sheep, causing symptoms such as fever, facial edema, cyanosis of the tongue, oral lesions, lameness, and high mortality. Cattle serve as a subclinical reservoir. Controlling BTV is a crucial challenge in livestock farming, requiring the identification of innovative vaccination strategies that induce effective immunity against the various circulating serotypes. In this context, the "vaccine paradox" of BTV emerges, revealing a discrepancy between the proven immunological efficacy of available vaccines and their inability to ensure stable epidemiological control. This paper investigates the reasons for this discrepancy and clarifies the structural limitations that prevent current vaccination strategies from achieving this.