Detection of Mycobacterium avium Subspecies Paratuberculosis from Intestinal and Nodal Tissue of Dogs and Cats

Objective. To determine prevalence of MAP in intestinal and nodal tissue from dogs and cats at necropsy at Kansas State University and to determine if an association existed between presence of MAP and gastrointestinal inflammation, clinical signs, or rural exposure. Procedures. Tissue samples were collected from the duodenum, ileum, and mesenteric and colic nodes of adult dogs (73) and cats (37) undergoing necropsy for various reasons. DNA was extracted and analyzed for insertion sequence 900 using nested PCR. Positive samples were confirmed with DNA sequencing. An online mapping system was used to determine if patients lived in an urban or rural environment based on the home address. Medical records were reviewed for clinical signs and histological findings at necropsy. Results. MAP was identified from 3/73 (4.1%) dogs and 3/37 (8.1%) cats. There was no documented association between presence of MAP and identification of histologic-confirmed gastrointestinal inflammation, gastrointestinal clinical signs, or exposure to a rural environment. Conclusion and Clinical Relevance. MAP-specific DNA can be identified within the intestinal and nodal tissue of dogs and cats that do not have pathological lesions or clinical signs consistent with gastrointestinal disease. The significance of this organism’s presence without associated gastrointestinal pathology is unknown. 1. Introduction Mycobacterium avium subspecies paratuberculosis (MAP) is the bacterial etiologic agent of Johne's disease, a severe chronic debilitating gastrointestinal disease of ruminants. Infection from this bacterium is responsible for substantial morbidity, mortality, and economic loss in cattle in the United States [1]. Within herds, MAP is transmitted mainly by ingestion of food or water contaminated with infected feces, but it can also be transmitted to offspring in utero or via infected milk [2, 3]. Clinical and histopathologic similarities between Johne's disease and Crohn’s disease in humans, which is characterized by a chronic granulomatous ileocolitis, have led researchers to suspect MAP as an etiologic agent for Crohn’s disease as well. Although MAP has been identified from clinical tissues of patients with Crohn’s disease, Koch’s postulates have not been proven to establish this link definitively [4, 5]. Investigation of MAP’s potential contribution to gastrointestinal disease in dogs and cats is in its infancy. While both classic tuberculosis (including M tuberculosis and M bovis) and opportunistic mycobacteriosis (including M fortuitum) have been described extensively in dogs