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.
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.
authors: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand. Electronic address: R.Dukkipati@massey.ac.nz.
authors: Venkata S R
authors: VSR
authors: Dukkipati
authors: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors: Anne L
authors: AL
authors: Ridler
authors: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors: Keith G
authors: KG
authors: Thompson
authors: AgResearch, Hopkirk Research Institute, Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand.
authors: Bryce M
authors: BM
authors: Buddle
authors: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors: Barry A
authors: BA
authors: Hedgespeth
authors: AgResearch, Hopkirk Research Institute, Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand.
authors: Marian
authors: M
authors: Price-Carter
authors: Faculty of Veterinary Science, University of Sydney, Private Bag 3, Camden, NSW 2570, Australia.
authors: Douglas J
authors: DJ
authors: Begg
authors: Faculty of Veterinary Science, University of Sydney, Private Bag 3, Camden, NSW 2570, Australia.
authors: Richard J
authors: RJ
authors: Whittington
authors: Unité de Génétique Mycobactérienne, Institut Pasteur, Paris Cedex 15, France.
authors: Brigitte
authors: B
authors: Gicquel
authors: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand; Unité de Génétique Mycobactérienne, Institut Pasteur, Paris Cedex 15, France.
authors: Alan
authors: A
authors: Murray
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D001835:Body Weight; D007371:Interferon-gamma / Q000097:blood; D008297:Male; D016927:Mycobacterium avium subsp. paratuberculosis; D010283:Paratuberculosis / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology*
chemical_list: D007371:Interferon-gamma
keywords: Antibodies; Experimental infection; Faecal cultures; IFN-γ responses; Immune responses; Johne’s disease; Merino; Mycobacterium avium subspecies paratuberculosis; OJD; Paratuberculosis; Sheep; Tissue cultures