Field evaluation of YURVAC® RHD vaccine-induced humoral immunity in intensive meat rabbit farms

Abstract Rabbit haemorrhagic disease virus (RHDV) remains one of the most important pathogens of domestic rabbits, combining high mortality rates with marked environmental resilience and rapid spread in intensive production systems. Rabbit haemorrhagic disease (RHD) is listed by the World Organisation for Animal Health (WOAH), underscoring its relevance for veterinary surveillance, outbreak reporting and international rabbit health management. The emergence and global dissemination of GI.2 (RHDV2), together with its limited cross-protection by classical GI.1-based vaccines, has driven the development of a new generation of vaccines. However, quantitative field data on their performance under real production conditions are still scarce. This cross-sectional study evaluated the humoral response to YURVAC ® RHD, a recombinant virus-like particle (VLP) vaccine, in six intensive meat rabbit farms in mainland Portugal. A total of 351 rabbits were sampled, comprising 327 breeding does vaccinated semiannually and 24 unvaccinated fattening rabbits aged 35–70 days. Anti-RHDV antibodies were measured using an in-house indirect ELISA. Overall, 341/351 rabbits (97.2%) had detectable anti-RHDV antibodies against at least one of the two VLP antigens tested. Among vaccinated breeding does, 323/327 animals were seropositive, yielding a seropositivity rate of 98.8% in the reproductive group. In the fattening group, 18/24 rabbits were seropositive (75.0%), suggesting the presence of maternally derived antibodies. The findings show that semiannual vaccination with YURVAC ® RHD was associated with high and consistent seropositivity and a strong humoral response in breeding does under intensive field conditions. The serological profile of unvaccinated fattening rabbits supports maternal antibody transfer but also indicates a potential vulnerability window later in the production cycle, reinforcing the value of field-based serological monitoring in intensive rabbit production.