Effects of vaccination against paratuberculosis on tuberculosis in goats: diagnostic interferences and cross-protection

Evaluation of interferon-γ (IFN-γ) secretion induced by avian and bovine tuberculins (PPD) showed a predominant avian PPD-biased response in the vaccinated group from week 4 post-vaccination onward. Although 60% of the animals were bovine reactors at week 14, avian PPD-biased responses returned at week 16. After challenge with M. caprae, the IFN-γ responses radically changed to show predominant bovine PPD-biased responses from week 18 onward. In addition, cross-reactions with bovine PPD that had been observed in the vaccinated group at week 14 were reduced when using the M. tuberculosis complex-specific antigens ESAT-6/CFP-10 and Rv3615c as new DIVA (differentiation of infected and vaccinated animals) reagents, which further maintained sensitivity post-challenge. Ninety percent of the animals reacted positively to the tuberculin cervical comparative intradermal test performed at 12 weeks post-infection. Furthermore, post-mortem analysis showed reductions in tuberculous lesions and bacterial burden in some vaccinated animals, particularly expressed in terms of the degree of extrapulmonary dissemination of TB infection.Our results suggest a degree of interference of PTB vaccination with current TB diagnostics that can be fully mitigated when using new DIVA reagents. A partial protective effect associated with vaccination was also observed in some vaccinated animals.Caprine tuberculosis (TB), caused either by Mycobacterium bovis or M. caprae, and paratuberculosis (PTB), caused by M. avium subsp. paratuberculosis (Map), are endemic diseases in goat herds of the Iberian Peninsula [1-3]. Both infections may have an impact in terms of economic loss. Moreover, M. caprae and Map can be transmitted between domestic hosts and wildlife species [2,4]. In addition, M. caprae is a zoonotic agent [5-7] and Map has been associated with Crohn’s disease [8,9].Control of PTB in small ruminants can be facilitated by vaccination because the bacterial burden is greatly reduced, containing