Changes

===Pathogenesis===

===Pathogenesis===

* Organisms get in through the M-cells of [[Peyer's Patches - Anatomy & Physiology|Peyer's patches]].  

Organisms penetrate the M-cells of the [[Peyer's Patches - Anatomy & Physiology|Peyer's patches]].  

* Mycobacteria invade macrophages and cause a granulomatous inflammatory response.

Mycobacteria invade macrophages and cause a granulomatous inflammatory response.

* Death results from:  

Death may result from:  

** Damage to the mucosa.

** Damage to the mucosa.

*** Nutrients cannot be absorbed.

**Nutrients cannot be absorbed.

** Inflammatory loss of protein

** Inflammatory loss of protein

 

===Pathology===

===Pathology===

====Gross====

====Gross====

[[Image:johnes disease proliferative enteritis.jpg|thumb|right|150px|Johnes Disease (Courtesy of Bristol BioMed Image Archive)]]

[[Image:johnes disease proliferative enteritis.jpg|thumb|right|150px|Johnes Disease (Courtesy of Bristol BioMed Image Archive)]]

 

* Cows appear very emaciated.

The infected host appears emaciated.

 

*** Fat is pale and oedematous, and there is not much of it.   

*** Fat is pale and oedematous, and there is not much of it.   

* Signs are confined to the terminal [[Small Intestine - Anatomy & Physiology|small intestine]] (especially the [[Ileum - Anatomy & Physiology|ileum]]) but are characteristic.  

* Signs are confined to the terminal [[Small Intestine - Anatomy & Physiology|small intestine]] (especially the [[Ileum - Anatomy & Physiology|ileum]]) but are characteristic.