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Proceedings of the 10th International Colloquium on Paratuberculosis

Proceedings of the 10th International Colloquium on Paratuberculosis

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#159 Experimental infecti<strong>on</strong> in adult sheep and lambs with Mycobacterium avium subsp<br />

paratuberculosis (Map) at two different doses<br />

Laetitia Delgado, Maria Muñoz, Carlos Garcia-Pariente, Miguel Fuertes, Julio Benavides, Jorge G<strong>on</strong>zalez, M<br />

Carmen Ferreras, J Francisco Garcia-Marin, Valentin Perez,<br />

Universidad de Le<strong>on</strong>, Spain<br />

Objective: To establish <str<strong>on</strong>g>the</str<strong>on</strong>g> effect <str<strong>on</strong>g>of</str<strong>on</strong>g> age and doses <str<strong>on</strong>g>of</str<strong>on</strong>g> Map up<strong>on</strong> susceptibility to Johne´s disease in ovine.<br />

Materials and Methods: Sixteen 1,5-m<strong>on</strong>th-old lambs out <str<strong>on</strong>g>of</str<strong>on</strong>g> 24 and 22 adult sheep (over two years old)<br />

out <str<strong>on</strong>g>of</str<strong>on</strong>g> 28 were experimentally challenged orally and both divided into two groups infected: a) with a high dose<br />

(1.1x1010 CFU), b) with a lower dose (1.1x103 CFU) <str<strong>on</strong>g>of</str<strong>on</strong>g> an ovine field strain <str<strong>on</strong>g>of</str<strong>on</strong>g> Map. The remaining animals<br />

were used as unchallenged c<strong>on</strong>trol groups.<br />

Peripheral cellular and humoral immune resp<strong>on</strong>ses were assessed as well as Map fecal shedding between<br />

0 and 210 dpi. Sixteen challenged and five c<strong>on</strong>trol animals were slaughtered at 120 dpi, and <str<strong>on</strong>g>the</str<strong>on</strong>g> remaining<br />

at 210dpi. Histological and bacteriological studies were c<strong>on</strong>ducted in samples <str<strong>on</strong>g>of</str<strong>on</strong>g> intestine and related<br />

lymphoid tissue (Peyer´s patches and lymph nodes). Animals were classified according to <str<strong>on</strong>g>the</str<strong>on</strong>g>ir lesi<strong>on</strong>s and<br />

granulomas were counted in 3 tissue secti<strong>on</strong>s from each sample.<br />

Results: No gross lesi<strong>on</strong>s were observed in any <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> animals. Only <str<strong>on</strong>g>the</str<strong>on</strong>g> high dose-challenged groups<br />

showed histological lesi<strong>on</strong>s associated with paratuberculosis (92.3% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> adult sheep and 100% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

lambs). However, those c<strong>on</strong>sisted <str<strong>on</strong>g>of</str<strong>on</strong>g> few small demarcated focal granulomas restricted to <str<strong>on</strong>g>the</str<strong>on</strong>g> lymphoid tissue<br />

(mostly Peyer´s patches) in <str<strong>on</strong>g>the</str<strong>on</strong>g> adults, whereas <str<strong>on</strong>g>the</str<strong>on</strong>g>se were more numerous, larger and spreading to <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

lamina propia in <str<strong>on</strong>g>the</str<strong>on</strong>g> lambs. The tissue and faeces culture were positive in 5 high dose-challenged lambs. Cellular<br />

immune resp<strong>on</strong>ses appeared earlier in <str<strong>on</strong>g>the</str<strong>on</strong>g> adult sheep than in lambs.<br />

C<strong>on</strong>clusi<strong>on</strong>s: Adult sheep can be infected, as seen by <str<strong>on</strong>g>the</str<strong>on</strong>g> development <str<strong>on</strong>g>of</str<strong>on</strong>g> characteristic lesi<strong>on</strong>s; however,<br />

<str<strong>on</strong>g>the</str<strong>on</strong>g>y seem to be able to c<strong>on</strong>trol <str<strong>on</strong>g>the</str<strong>on</strong>g> progressi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> disease. The dose <str<strong>on</strong>g>of</str<strong>on</strong>g> Map plays an important role<br />

in <str<strong>on</strong>g>the</str<strong>on</strong>g> establishment <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> infecti<strong>on</strong> both in adult sheep and lambs.<br />

136

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