Study about two challenges of rabbit production: characterization of recent s. Aureus ourbreaks and assessment of the health of rabbit does (oryctolagus cuniculus) in five different housing systems

• Autores: Sara Pérez Fuentes
• Directores de la Tesis: Juan Manuel Corpa Arenas (dir. tes.), Laura Selva Martínez (codir. tes.)
• Lectura: En la Universidad CEU - Cardenal Herrera ( España ) en 2020
• Idioma: español
• Tribunal Calificador de la Tesis: Juan José Pascual Amorós (presid.), Juan José Quereda Torres (secret.), Cristina Zomeño (voc.), Davi Savietto (voc.), M. Angeles Tormo Mas (voc.)
• Materias:
  • Ciencias agrarias
    • Ciencias veterinarias
      • Patología
• Enlaces
  • Tesis en acceso abierto en: Repositorio Institucional CEU
• Resumen

  • Rabbit production faces a wide variety of challenges today, being staphylococcal infections and welfare of rabbit does two of the most important ones. In rabbits, Staphylococcus aureus is a bacterium that mainly produces mastitis, pododermatitis, abscesses and pyoderma, generating numerous economic losses in the affected farms. But the population of S. aureus is very heterogeneous, and it is necessary to perform a typing to characterize the strains present in each farm and to help its prevention and treatment. The most frequent clones in rabbitries were ST121 (high virulent strains) and ST96 (low virulent strains). However, in recent years, veterinarians and farmers have expressed their concern about the emergence of more virulent and persistent outbreaks. Considering that S. aureus has a great adaptation capacity, it was suggested that the clones could have changed or acquired new virulence factors or even new clones could have appeared, causing this increase in the number and virulence of the outbreaks in rabbit farms. Therefore, the objectives of the first part of this thesis were to characterize genetically the isolated strains from rabbit farms, to study their geographical distribution and to test in vivo some of these strains to verify whether the observed genetic changes correlated with a greater infective capacity. A new variant of the ST121 was detected, reaching the 19% of all isolates. This clone was detected for the first time in 2014 in the northwest of the Iberian Peninsula and later it spread to the east. Similarly, a variant of ST96 clone was isolated from staphylococcal infections throughout the whole Iberian Peninsula. In addition, new clones not described previously in rabbits in Spain have also isolated, such as ST1, ST146 and ST398. The complete sequencing of these new clones has evidenced the acquisition of mobile genetic elements, with the exception of CC96 strains. Most of them had lost the phage with type 3 integrase, which not also carried the human IEC with the genes sak, chp and scn, but also truncated the sequence of β-haemolysin, causing these strains to express it. Finally, mutations in the dltb gene were found between strains of the CC96. All these changes could suggest an increase in virulence of the CC96 but they were not able to infect. In contrast, the new varian of ST121 infected a greater number of animals than their predecessor ST121, although it was not a significant increase. Therefore, the dissemination of new strains could be due to genetic changes not detected here or due to other factors extrinsic to the strains.

    The presence of S. aureus in the farms is closely related to the second challenge studied in this thesis, since the lesions produced by this bacterium greatly reduce animal welfare. In recent decades, concern about rabbit welfare and sustainability has increased. The housing system is a very important factor for animal welfare. However, information about how different available housing types for female rabbits affect their health status is scarce, but this is an important factor for their welfare. Hence the objective of this study was to evaluate the health status of female rabbits in five common housing systems: three different single-housing systems with distinct available surfaces and heights, a single-housing system with a platform and a collective system. The female rabbits in the collective and platform cages had higher cortisol concentrations in hair than those in the single-housing systems with no platform. The haptoglobin concentrations and kit mortality rates during lactation were higher for the collective-cage female rabbits. The collective group had more culled females and more lesions than the females in the other groups. The main reasons for culling in all the groups were reproductive problems and presence of abscesses, and the collective group of females was the most affected. In conclusion, keeping females in these collective systems negatively affected their health status and, therefore, their welfare. In contrast, individual housings caused lower concentrations of haptoglobin and hair cortisol (except for the cage with platform), less kit mortality rates and fewer culled females. This means a better sanitary status and greater welfare in individual housings, and therefore, they would be more indicated for female rabbits.