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==Pathogenesis==

==Pathogenesis==

''Mycobacterium paratuberculosis'' is 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 this usually occurs via ingestion of contaminated milk or colostrum. Environmental factors such as overcrowding and dirty pens may increase the risk of infection.  

''Mycobacterium paratuberculosis'' is 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 this usually occurs via ingestion of contaminated milk or colostrum. Environmental factors such as overcrowding and poor husbandry may increase the risk of infection.  

Following ingestion of ''M. paratuberculosis'' and uptake by the Peyer's Patches, infection begins in the ileum. ''M. paratuberculosis'' infects macrophages in the gastrointestinal tract and lymph nodes leading to a granulomatous inflammatory response. This leads to malabsorption and a protein-losing enteropathy.

Following ingestion of ''M. paratuberculosis'' and uptake by the Peyer's Patches, infection begins in the ileum. ''M. paratuberculosis'' infects macrophages in the gastrointestinal tract and lymph nodes leading to a granulomatous inflammatory response. This leads to malabsorption and a protein-losing enteropathy.