Changes

==Pathogenesis==

==Pathogenesis==

MAP is primarily spread through herds via faecal-oral transmission, contaminated water and in utero. Young animals are most susceptible to infection and usually become infected through ingestion of contaminated milk or colostrum. Environmental factors such as overcrowding and dirty pens may increase the risk of infection. Following ingestion of M. paratuberculosis, infection begins in the ileum. Following uptake by the Peyer's Patches, M. paratuberculosis infects macrophages in the gastrointestinal tract and lymph nodes leading to a granulomatous inflammatory response.

MAP is primarily spread through herds via faecal-oral transmission, contaminated water and in utero. Young animals less than a year of age are most susceptible to infection and usually become infected through ingestion of contaminated milk or colostrum. Environmental factors such as overcrowding and dirty pens may increase the risk of infection. Following ingestion of M. paratuberculosis, infection begins in the ileum. Following uptake by the Peyer's Patches, M. paratuberculosis infects macrophages in the gastrointestinal tract and lymph nodes leading to a granulomatous inflammatory response.

 

 

 

 

 

Animals with advanced '''stage 3''' will appear gaunt, and the meat is no longer deemed fit for human consumption.  Once the disease is present in the herd, it is ver difficult to get rid of it.

==Clinical Signs==

==Clinical Signs==

There is a long incubation period between infection and the development of clinical signs ranging from a year to several years. Animals may be affected subclinically before overt clinical signs are displayed. In the early stages, the disease is characterised by reduced milk production, reduced reproductive performance and increased susceptibility to infection or disease.

There is a long incubation period between infection and the development of clinical signs ranging from a year to several years. Animals may be affected subclinically before overt clinical signs are displayed. In the early stages, the disease is characterised by reduced milk production, reduced reproductive performance and increased susceptibility to infection or disease.

==Diagnosis==

==Diagnosis==  

 

Diagnosis is difficult, particularly in the case of subclinical disease as there is no single test that will detect all stages of the disease. The most commonly used diagnostic test is the ELISA which detects antibodies to ''M. paratuberculosis'' in clinically affected animals.

Diagnosis is difficult, particularly in the case of subclinical disease as there is no single test that will detect all stages of the disease. The most commonly used diagnostic test is the ELISA which detects antibodies to ''M. paratuberculosis'' in clinically affected animals.

Diagnosis is by; Histology, Serological tests, [[ELISA]] and AGID.

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60% of cases have lesions in [[Colon - Anatomy & Physiology|colon]] and [[Rectum - Anatomy & Physiology|rectum]] and can be diagnosed by rectal biopsy.

60% of cases have lesions in [[Colon - Anatomy & Physiology|colon]] and [[Rectum - Anatomy & Physiology|rectum]] and can be diagnosed by rectal biopsy.