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Created page with '* Paratuberculosis/ Johne's Disease is caused by ''Mycobacterium avium subsp. paratuberculosis''. * Causes enteritis and diarrhoea. * Usually seen in cattle, but can affect a…'
* Paratuberculosis/ Johne's Disease is caused by ''[[Mycobacterium avium subsp. paratuberculosis]]''.
* Causes enteritis and diarrhoea.
* Usually seen in cattle, but can affect all ruminants.
** May be seen in zoo ruminants and goat herds.
** Particularly prevalent in Channel Island breeds.
** Is now also becoming a problem in Limousin breeds.
* Produces a chronic proliferative enteritis.
* Is usually fatal, since the disease cannot be got rid of.
* Animals may sometimes be carriers without showing clinical signs.
** Once disease is present in a herd, it is very difficult to get rid of it.
* Mycobacterium is excreted in urine and milk as well as in the faeces.
===Clinical===
* Clinical signs develop in older cows after calving i.e. 3 to 4 years of age.
* '''BUT''' animals are infected as calves less than 6 months old
** The disease develops very slowly.
* Clinical signs include:
** Ongoing, chronic profuse diarrhoea.
*** Paint like consistency.
** Hindquarters and tail-caked with faeces
** Faeces also splattered on walls.
** Animal gradually fades away and dies over the course of months.
===Pathogenesis===
* Organisms get in through the M-cells of [[Peyer's Patches - Anatomy & Physiology|Peyer's patches]].
* Mycobacteria invade macrophages and cause a granulomatous inflammatory response.
* Death results from:
** Damage to the mucosa.
*** Nutrients cannot be absorbed.
** Inflammatory loss of protein
*** I.e. a [[Protein Losing Enteropathy|protein losing enteropathy]] (hypoalbuminaemia).
===Pathology===
====Gross====
[[Image:johnes disease proliferative enteritis.jpg|thumb|right|150px|Johnes Disease (Courtesy of Bristol BioMed Image Archive)]]
* Quite typical
* Cows appear very emaciated.
** Depends on how long the disease has been there.
** Not very much to see!
*** 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.
** Diffusely thickened mucosa
*** Transverse, corrugated ruggae with reddened crests.
**** Cannot extend the gut to remove these (i.e. they are permanent ruggae).
*** Velvety mucosal surface.
*** Mucosa may take on a 'corn-on-the-cob' appearance in advanced cases.[[Image:johnes disease proliferative ileitis.jpg|thumb|right|150px|Proliferative ileitis in Johnes disease (Courtesy of Bristol BioMed Image Archive)]]
** Serosal oedema.
** Distended lymphatics.
* Enlarged mesenteric lymph nodes.
* Changes are milder in sheep and goats.
** Often missed.
** May produce small areas of necrosis not usually seen in cattle.
** Sheep may get a pigmented form.
====Histologically====
[[Image:johnes disease histological.jpg|thumb|right|150px|Histological appearance of Johnes disease (Courtesy of Bristol BioMed Image Archive)]]
* Many large macrophages (epithelioid macrophages) in mucosa, submucosa and lymph nodes.
** Mesenteric lymph nodes are pale and enlarged (though not necrotic).
* The lamina propria is infiltrated by sheets of macrophages with some lymphocytes.
* Acid-fast bacteria are found in the macrophages and giant cells.
** Detected by Ziehl-Neelson stain.
** Bacteria act like foreign body producing a type IV hypersensitivity reaction.
* Sheep have two different forms.
*# '''Paucibacillary'''
*#* Many T cells
*#* Few bacilli
*# '''Multibacillary'''
*#* Many macrophages
*#* Many bacilli in macrophages
*#* Few lymphocytes
===Diagnosis===
* Diagnosis is by
** Histology
** Serological tests
*** ELISA & AGID
** Culture of organisms
** 60% of cases have lesions in [[Colon - Anatomy & Physiology|colon]] and [[Rectum - Anatomy & Physiology|rectum]] and can be diagnosed by rectal biopsy.[[Category:Enteritis,_Bacterial]][[Category:Enteritis, Proliferative]][[Category:Cattle]]
* Causes enteritis and diarrhoea.
* Usually seen in cattle, but can affect all ruminants.
** May be seen in zoo ruminants and goat herds.
** Particularly prevalent in Channel Island breeds.
** Is now also becoming a problem in Limousin breeds.
* Produces a chronic proliferative enteritis.
* Is usually fatal, since the disease cannot be got rid of.
* Animals may sometimes be carriers without showing clinical signs.
** Once disease is present in a herd, it is very difficult to get rid of it.
* Mycobacterium is excreted in urine and milk as well as in the faeces.
===Clinical===
* Clinical signs develop in older cows after calving i.e. 3 to 4 years of age.
* '''BUT''' animals are infected as calves less than 6 months old
** The disease develops very slowly.
* Clinical signs include:
** Ongoing, chronic profuse diarrhoea.
*** Paint like consistency.
** Hindquarters and tail-caked with faeces
** Faeces also splattered on walls.
** Animal gradually fades away and dies over the course of months.
===Pathogenesis===
* Organisms get in through the M-cells of [[Peyer's Patches - Anatomy & Physiology|Peyer's patches]].
* Mycobacteria invade macrophages and cause a granulomatous inflammatory response.
* Death results from:
** Damage to the mucosa.
*** Nutrients cannot be absorbed.
** Inflammatory loss of protein
*** I.e. a [[Protein Losing Enteropathy|protein losing enteropathy]] (hypoalbuminaemia).
===Pathology===
====Gross====
[[Image:johnes disease proliferative enteritis.jpg|thumb|right|150px|Johnes Disease (Courtesy of Bristol BioMed Image Archive)]]
* Quite typical
* Cows appear very emaciated.
** Depends on how long the disease has been there.
** Not very much to see!
*** 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.
** Diffusely thickened mucosa
*** Transverse, corrugated ruggae with reddened crests.
**** Cannot extend the gut to remove these (i.e. they are permanent ruggae).
*** Velvety mucosal surface.
*** Mucosa may take on a 'corn-on-the-cob' appearance in advanced cases.[[Image:johnes disease proliferative ileitis.jpg|thumb|right|150px|Proliferative ileitis in Johnes disease (Courtesy of Bristol BioMed Image Archive)]]
** Serosal oedema.
** Distended lymphatics.
* Enlarged mesenteric lymph nodes.
* Changes are milder in sheep and goats.
** Often missed.
** May produce small areas of necrosis not usually seen in cattle.
** Sheep may get a pigmented form.
====Histologically====
[[Image:johnes disease histological.jpg|thumb|right|150px|Histological appearance of Johnes disease (Courtesy of Bristol BioMed Image Archive)]]
* Many large macrophages (epithelioid macrophages) in mucosa, submucosa and lymph nodes.
** Mesenteric lymph nodes are pale and enlarged (though not necrotic).
* The lamina propria is infiltrated by sheets of macrophages with some lymphocytes.
* Acid-fast bacteria are found in the macrophages and giant cells.
** Detected by Ziehl-Neelson stain.
** Bacteria act like foreign body producing a type IV hypersensitivity reaction.
* Sheep have two different forms.
*# '''Paucibacillary'''
*#* Many T cells
*#* Few bacilli
*# '''Multibacillary'''
*#* Many macrophages
*#* Many bacilli in macrophages
*#* Few lymphocytes
===Diagnosis===
* Diagnosis is by
** Histology
** Serological tests
*** ELISA & AGID
** Culture of organisms
** 60% of cases have lesions in [[Colon - Anatomy & Physiology|colon]] and [[Rectum - Anatomy & Physiology|rectum]] and can be diagnosed by rectal biopsy.[[Category:Enteritis,_Bacterial]][[Category:Enteritis, Proliferative]][[Category:Cattle]]