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| − | ===[[Johnes disease|Johne's Disease (paratuberculosis)]]===
| + | #REDIRECT[[Johne's Disease]] |
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| − | *Johne's Disease is a chronic, contagious enteritis of ruminants
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| − | *Caused by ''M avium'' subsp. ''paratuberculosis''
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| − | *Epidemiology
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| − | **Transmitted to young calves by ingestion of mycobacteria in faeces of infected adults
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| − | **Organisms viable in environment for long periods
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| − | **Long incubation period with clinical signs appearing in cattle over 2 years of age
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| − | **Subclinical carriers can occur, shedding organisms in their faeces
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| − | *Pathogenesis and pathogenicity
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| − | **''M avium'' subsp. ''paratuberculosis'' is an intracellular pathogen
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| − | **Mycobacteria are ingested by macrophages in the Peyer's patches
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| − | **Survival and replication of mycobacteria in macrophages initiate an immune-mediated granulomatous reaction
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| − | **Lymphocytes and macrophages accumulate in the lamina propria and submucosa, resulting in marked thickening and folding of the intestinal wall
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| − | **Mesenteric lymph nodes are enlarged
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| − | **A protein-losing enteropathy results, along with failure to absorb nutrients and water
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| − | *Clinical signs
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| − | **Diarrhoea, initially intermittent, and weight loss in cattle
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| − | **Weight loss in sheep and goats
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| − | **Rapidly fatal with weight loss and diarrhoea in some deer
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| − | *Diagnosis
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| − | **All diagnostic procedures have faults but include:
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| − | **Microscopy of rectal biopsies
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| − | **Faecal culture
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| − | **Serology of serum including complement fixation tests, agar-gel immunodiffusion test and an ELISA
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| − | **Histopathology of intestines and lymph nodes
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| − | **Isolation and identification of mycobacteria from faeces and tissues
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| − | **Ziehl-Neelson-positive smears
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| − | **Intradermal tuberculin test
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| − | **DNA probes for detection in faeces
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| − | *Control
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| − | **Slaughter of affected animals
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| − | **Detection and slaughter of subclinical shedders using faecal culture, DNA probes and ELISA
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| − | **Good hygiene to protect young calves
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| − | **Separation and isolation of calves from affected dams
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| − | **Inactivated adjuvanted vaccines are available and reduce shedding of mycobacteria but do not eliminate infection
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| − | [[Category:Mycobacterium_species]][[Category:Cattle]]
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