Paratuberculosis diagnosis in calves experimentally infected with argentinean isolates.

FERNÁNDEZ, B.; COLAVECCHIA, SB.; JOLLY, A; MINATEL, L.; STEMPLER, A; FORTUNY, M. L.; INGRATTA, G; HAJOS S; PAOLICCHI, F.A.; MUNDO, S. L.

Canela

Simposio; VII Meeting of theSLAMTB; 2014

Sociedad Latinoamericana de Tuberculosis y otras micobacterias

Background and objective: Johne?s disease, caused by Mycobacterium avium subsp. paratuberculosis (Map), is a chronic granulomatous enteritis affecting ruminants. The aim of this work was to evaluate fecal culture, serology, IFN-γ production, intradermal test and histopathology in order to indentify infection in experimental challenged calves. Methods: Two month old-Holstein calves were infected with 200 mg wet weight of two different bovine Map isolates (two RFLP patterns: A, n=3; C, n=2) or mock infected (MI, n=2). Fecal cultures, specific IgG, IgG1 and IgG2 against Map-protoplasmic antigen (PPA) and Map whole bacteria (wMap), avian purified protein derivative (PPDa) and bovine purified protein derivative (PPDb) specific IFN-γ production were evaluated monthly. Intradermal test (IT) and histopathology were studied at 160 and 180 days post-infection (dpi) respectively. Results: Map-infected calves (4/5) were positive to fecal culture and the isolates were confirmed by IS900-PCR. Map-infected animals were not detected by PPA-ELISA for IgG meanwhile, wMap-ELISA could identify Infected calves (4/5), since 80 dpi. Interestingly, the use of anti-bovine IgG2 improved the identification of Map-infected calves by both ELISAs (5/5). IFNγ production was variable, detecting an increase of PPDa specific in A at 90 dpi. In addition, all infected calves showed reactivity by IT and incipient granulomatous lesions by histopathology. Conclusion: Our results demonstrate the development of an early humoral immune response in Map-experimentally infected calves and suggest that serological diagnostic tools currently applied might be reconsidered. Diagnostic strategies should be modified (new antigens and isotypes targeted) in order to improve identification of Map-infected