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  • Title: Experimental infection of New Zealand Merino sheep with a suspension of Mycobacterium avium subspecies paratuberculosis (Map) strain Telford: Kinetics of the immune response, histopathology and Map culture.
    Author: Dukkipati VSR, Ridler AL, Thompson KG, Buddle BM, Hedgespeth BA, Price-Carter M, Begg DJ, Whittington RJ, Gicquel B, Murray A.
    Journal: Vet Microbiol; 2016 Nov 15; 195():136-143. PubMed ID: 27771059.
    Abstract:
    A long-term study was undertaken to monitor immune responses, faecal cultures and clinical disease in sheep experimentally infected with Mycobacterium avium subspecies paratuberculosis (Map) strain Telford. New Zealand Merino lambs (N=56) were challenged with three oral doses of Map suspension. The lambs were weighed and faecal and blood samples obtained at different time-points. At 63 weeks post-challenge, surviving sheep were euthanised and samples of liver, ileo-caecal valve and mesenteric lymph node were collected for histopathology and Map culture. High IFN-γ and antibody responses were evident as early as 8 weeks post-C1 which persisted until the end of the trial. Approximately 92% of the sheep shed Map in faeces at 36 weeks post-challenge, with the prevalence decreasing to around 40% at the end of the trial. Thirteen sheep progressively lost weight and were euthanised between weeks 32 and 58 post-challenge. Nearly 58% of surviving sheep exhibited histo-pathological lesions in at least one of the three tissues sampled, while 42% showed acid-fast bacilli in at least one tissue. A positive Map culture in at least one tissue was obtained from approximately 85% of sheep. These results indicate that the three doses of Map challenge were highly effective in establishing Johne's disease in NZ Merino lambs.
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