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==Description==

==Description==

'''Tuberculosis''' in cattle is caused by ''[[Mycobacterium bovis]]''. It is a chronic disease characterised by nodular lesions in any organ, although the respiratory system is most commonly affected. The nodules often become nectroic with a caseous centre. The primary lesions may disseminate to involve other body systems.  

'''Tuberculosis''' in cattle is caused by ''[[Mycobacterium bovis]]''. It is a chronic disease characterised by granulomatous nodular lesions in any organ, although the respiratory system is most commonly affected. The nodules often become nectroic with a caseous centre. The primary lesions may disseminate to involve other body systems.  

A higher level of infection is required to establish the alimentary form of the disease and this is reflected by its lower incidence in comparison to the respiratory form.  

A higher level of infection is required to establish the alimentary form of the disease and this is reflected by its lower incidence in comparison to the respiratory form.  

   

   

Inhalation of ruminal gases is the most common route of entry for the mycobacterium organism, and spread of the disease is usually via cow to cow contant. Cattle can also become infected by ingestion of the causative agent, this is thought to be the route of entry when the badger is involved, by infecting grazing land or water troughs. Calves with infected dams can become affected via the milk, and intrauterine infection at coitus has been reported.   

Inhalation of ruminal gases is the most common route of entry for the mycobacterium organism, and spread of the disease is usually via cow to cow contact. Cattle can also become infected by ingestion of the causative agent, this is the usual route of entry when the badger is involved, by infecting grazing land or water troughs. Calves with infected dams can become affected via the milk, and intrauterine infection at coitus has been reported.   

   

   

Historically bovine TB was a major cuase of human TB, but the introduction of tuberculin testing and slaughter, meat inspection at abatoirs, the pasturisation of milk and the BCG vaccination has dramatically reduced transmission to humans and bovine TB as a cuase of human disease is now very low indeed.

Historically bovine TB was a major cause of human TB, but the introduction of tuberculin testing and slaughter, meat inspection at abatoirs, the pasturisation of milk and the BCG vaccination has dramatically reduced transmission to humans and bovine TB as a cuase of human disease is now very low indeed.

The disease is of serious economic importance to farmers becasue of the stringent control measures which remain in place. These include the slaughter of infected animals and movement restrictions placed on farms with reactors or inconclusive results.  

The disease is of serious economic importance to farmers becasue of the stringent control measures which remain in place. These include the slaughter of infected animals and movement restrictions placed on farms with reactors or inconclusive results.

==Signalment==

==Signalment==