Changes

==Description==

==Description==

'''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.  

'''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 necrotic 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 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.   

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 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.

Historically bovine TB was a major cause of human TB, but the introduction of tuberculin testing and slaughter, meat inspection at abattoirs, the pasteurisation of milk and the BCG vaccination has dramatically reduced transmission to humans and bovine TB as a cause 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 because 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==

The disease usually affects heifers or young stock but cases can occur in cattle of any age. TB is more common in dairy herds.

The disease usually affects heifers or young stock but cases can occur in cattle of any age. TB is more common in dairy herds.

   

   

Incidence of the disease has increased over the past 15 years; it is prevelent in '''Wales''' and the south west of England but is re-emerging in other parts of the UK such as the west Midlands and north-west England.

Incidence of the disease has increased over the past 15 years; it is prevalent in '''Wales''' and the '''southwest''' of England but is re-emerging in other parts of the UK such as the west Midlands and northwest England.

Most warm blooded animals are susceptible to bovine TB and can act as a resevoir for infection. The disease in cattle has been associated with wildlife species in a number of countries; the European badger and red deer in the UK, opossums and ferrets in New zealand, mule deer, white-tailed deer, elk, and bison in North America and water buffalo in Australia.  

Most warm blooded animals are susceptible to bovine TB and can act as a resevoir for infection. The disease in cattle has been associated with wildlife species in a number of countries; the European badger and red deer in the UK, opossums and ferrets in New zealand, mule deer, white-tailed deer, elk, and bison in North America and water buffalo in Australia.  

      

      

==Diagnosis==

==Diagnosis==

The intradermal comparative tuberculin test is widely used in the UK for diagnosis of the disease. Two injections are give subcutaneously in the neck of cattle, one is avian and the second bovine tuberculin purified protein derivative (PPD). The thickness of the skin is recorded at each injection site. The test is read 72 hours later, and the thickness of the skin is remeasured. Interpretation is based on finding a swelling or increase in skin thinkness at the site of the injection. A comparison must be made between the reaction to avian and the bovine tuberculin to account for cross reactivity with related diseases, such as atypical mycobacteriosis, or paratuberculosis- Johne's disease.  

The intradermal comparative tuberculin test is widely used in the UK for diagnosis of the disease. Two injections are give subcutaneously in the neck of cattle, one is '''avian''' and the second '''bovine''' '''tuberculin purified protein derivative''' (PPD. The thickness of the skin is recorded at each injection site. The test is read after '''72 hours''', and the thickness of the skin is remeasured. Interpretation is based on finding a swelling or increase in skin thinkness at the site of the injection. A comparison must be made between the reaction to avian and the bovine tuberculin to account for cross reactivity with related diseases, such as atypical mycobacteriosis, or paratuberculosis- Johne's disease.  

A single intradermal test is used in many countries but has the disadvantage of giving reactors to avian tuberculosis and Johne's disease.  

A single intradermal test is used in many countries but has the disadvantage of giving reactors to avian tuberculosis and Johne's disease.  

Location and severity depend on which body systems are affected and the advancement of the disease. Due to the tesing and slaughter policy most cases in the UK are idenified before development of clinical signs.  

Location and severity depend on which body systems are affected and the advancement of the disease. Due to the tesing and slaughter policy most cases in the UK are idenified before development of clinical signs.  

====Respiratory form====

====Respiratory form===

* Chronic cough- soft and productive

* Chronic cough- soft and productive=

* Tachypnoea  

* Tachypnoea  

* Dyspnoea

* Dyspnoea

* Dull areas on auscultation of the lungs in advanced cases

* Dull areas on auscultation of the lungs in advanced cases

====Alimentary form====

====Alimentary form===

* Few clinical signs

* Few clinical signs=

* Diarrhoea

* Diarrhoea

* Bloat

* Bloat