Association of severity of enteric granulomatous inflammation with disseminated Mycobacterium avium subspecies paratuberculosis infection and antemortem test results for paratuberculosis in dairy cows

College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1681, USA.
Veterinary Microbiology (Impact Factor: 2.51). 04/2008; 131(1-2):154-63. DOI: 10.1016/j.vetmic.2008.02.017
Source: PubMed


Disseminated infection (DI) of Mycobacterium avium subspecies paratuberculosis (MAP) in cattle may impair cow health, potentiate spread of disease, and is a potential food-safety risk. The objectives of this study were to determine the association between severity of histologic enteric lesions and the occurrence of DI, clinical signs, and positive fecal culture and serum ELISA results. Bacteriologic fecal culture and serum ELISA were performed on 40 dairy cows from MAP-infected herds. Cows were classified as having DI if MAP was isolated from any of 11 extra-intestinal tissues collected postmortem. A grade of 0-3, corresponding to the severity of histologically evident granulomatous inflammation was determined for sections of ileum, jejunum, mesenteric lymph node, and ileocolic lymph node. An overall intestinal inflammation (OII) grade of 0-3 was assigned to each cow. The proportion of cows with DI increased with tissue-specific lesion grade and OII grade. All cows with grade 3 inflammation in any single tissue had DI, however, some cows with DI had grade 1 inflammation or no lesions. In general, there was a positive association between OII grade and clinical signs, gross enteric lesions, and positive ELISA and fecal culture results. However, 12% of OII grade 0 cows had clinical signs (explained by other conditions recognized with necropsy), and the proportion of positive ELISA results was lower for OII grade 3 cows relative to grade 2 cows. Although MAP dissemination may occur early in the disease process, histopathology of intestinal tissues may be used to detect a substantial proportion of DI cows.

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    • "paratuberculosis (MAP) is the causative agent for Johne's disease, a highly-infectious wasting disease that affects a range of domestic ruminants including cattle, sheep, goats and deer[1]. Johne's disease presents as a wasting disease which can include persistent diarrhoea, sub-mandibular oedema, and progressive emaciation, ultimately leading to death or premature culling of the infected animal[2]. Some infected animals may be asymptomatic and not show any clinical signs of infection, however both symptomatic and asymptomatic animals can shed MAP in their milk and faeces, thereby constituting an infectious risk to susceptible animals which typically acquire infection through the ingestion of MAP or MAP contaminated material[3,4,5]. "
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    ABSTRACT: Johne's disease or paratuberculosis is a chronic granulomatous inflammation of the small intestine of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Recent studies suggest an association between MAP and Crohn's disease in humans. MAP can become widely distributed within the tissues of infected animals, and meat may be a possible route of exposure of MAP to humans. In this study, 47 dairy and beef cattle were examined for the occurrence of viable MAP in diaphragm muscle. At the slaughterhouse, gut tissues, diaphragm muscle, blood, and feces of the 47 animals were collected for bacteriological culture, as well as gut samples for histopathological analysis. MAP was detected by bacteriological culture and conventional and real-time IS900 polymerase chain reaction in the diaphragm muscle of six infected cattle at slaughter (13%). The six animals showing evidence of MAP in diaphragm muscle had diffuse lesions and severe granulomatous inflammation in ileocecal lymph nodes, jejunal lymph nodes, ileocecal valve, and ileum. All six had heavy bacterial load in mesenteric lymph nodes, ileocecal valve, ileum, and jejunum, and four showed clinical signs of paratuberculosis. Two animals did not show clinical signs but had viable MAP in intestinal tissues and in diaphragm muscle as well. MAP was found in blood of only one of the six animals showing evidence of MAP in diaphragm muscle and in feces of three of them. In general, there was a positive association between enteric lesion severity, clinical signs of paratuberculosis, heavy bacterial load in intestinal tissues, fecal shedding of MAP, and the presence of disseminated MAP infection in diaphragm muscle. The results of this study demonstrated that MAP can be detected and cultured from muscle of MAP-infected cattle destined for human consumption and suggest a possible risk of exposure of humans to MAP via contaminated meat.
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