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| If the mycobacteria disseminated from the primary complex then lymph nodes in other regions will also be affected and there will be multiple small foci of infection on other organs. | | If the mycobacteria disseminated from the primary complex then lymph nodes in other regions will also be affected and there will be multiple small foci of infection on other organs. |
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| ==Treatment== | | ==Treatment== |
| Treatment is not usually an option due to the chronic nature of the disease, zoonotic potential and test and slaughter policy. | | Treatment is not usually an option due to the chronic nature of the disease, zoonotic potential and test and slaughter policy. |
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| The mycobacterium reside within macrophages in the lungs where they multiply and result in characteristic [[Lungs Inflammatory - Pathology#Granulomatous pneumonia|granulomatous inflammation]] The regional lymph nodes and also affected | | The mycobacterium reside within macrophages in the lungs where they multiply and result in characteristic [[Lungs Inflammatory - Pathology#Granulomatous pneumonia|granulomatous inflammation]] The regional lymph nodes and also affected |
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− | **90% of cases exhibit the pulmonary form
| + | Microscopically: |
− | **Grossly:
| + | Epithelioid cells, with large vesicular nuclei and pale cytoplasm and giant cells, formed by the fusion of macrophages, are found at the centre of tubercles. Surrounding this there is a narrow layer of lymphocytes, mononuclear cells and plasma cells, more advanced cases show peripheral fibroplasia and central necrosis. |
− | ***Ulcers in [[Trachea Inflammatory - Pathology|trachea]] and [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchi]] due to coughed up bacteria
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− | ***Spreads into [[Pleural Cavity & Membranes Inflammatory - Pathology|pleura]]
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− | **Microscopically:
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− | ***Epitheliod and giant cells at centre of tubercles
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− | ****Macrophages with ingested bacteria, forming epithelioid cells - large vesicular nuclei, abundant pale cytoplasm
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− | ****Giant cells, formed by fusion of macrophages, with multiple nuclei
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− | ***Narrow layer of lymphocytes, mononuclear cells and plasma cells at the periphery of the tubercle
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− | ***With time, peripheral fibroplasia and central necrosis develop
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− | *If the infection is not contained in the primary complex described above, the mycobacteria can disseminate via lymphatics to other organs and lymph nodes
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− | *This can allow the development of '''miliary tuberculosis''', i.e. numerous small foci of infection in many organs/ tissues
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− | *some tubercle bacilli enter the lymph and travel to the bronchial or mediastinal nodes
| + | phagocytosed by alveolar macrophages |
− | *inhaled bacilli reach the alveoli, set up a focus of inflammation
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− | *phagocytosed by alveolar macrophages
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| *two processes may develop if the animal has not encountered the organism before: | | *two processes may develop if the animal has not encountered the organism before: |
| :- the organism may grow in the phagocytes as intracellular parasites | | :- the organism may grow in the phagocytes as intracellular parasites |
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| ::- ultimately, macrophages are killed and infection spreads | | ::- ultimately, macrophages are killed and infection spreads |
| :- the organism may be broken down and some antigens taken up by the immune system | | :- the organism may be broken down and some antigens taken up by the immune system |
− | ::- cell mediated immune system produces cytotoxic T-lymphocytes
| + | cell mediated immune system produces cytotoxic T-lymphocytes which attack and destroy infected cells, leading to a type IV hypesensitivity reaction. |
− | ::- T-lymphocytes can attack and destroy cells harbouring bacilli
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− | ::- leads to type IV (delayedd type) hypesensitivity
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− | ::- 'caseous' or cheesy type of necrosis
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− | | |
− | =====Tuberculosis pleurisy=====
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− | caseous lymph node ruptures results from extensive tissue necrosis
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− | if located in lung alveoli, the follicle may rupture into a bronchus, causing spread of the disease to all the other lobules served by that bronchus
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− | the necrosis may erode the wall of a large pulmonary vessel resulting in fatal haemoptysis.
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| [[Category:Cattle]][[Category:To_Do_- lizzyk]] | | [[Category:Cattle]][[Category:To_Do_- lizzyk]] |
| [[Category:Respiratory_Bacterial_Infections]] | | [[Category:Respiratory_Bacterial_Infections]] |
| [[Category:zoonoses]] | | [[Category:zoonoses]] |