Proceedings of the 10th International Colloquium on Paratuberculosis

#144 The suitability <strong>of</strong> macroscopic preselection for prevalence estimation <strong>of</strong> bovine
paratuberculosis at <strong>the</strong> slaughterhouse
Julia Elze, Heike Köhler, Elisabeth Liebler-Tenorio
Institute <strong>of</strong> Molecular Pathogenesis, Friedrich-Loeffler-Institute, Jena, Germany
Objective: To examine <strong>the</strong> probability <strong>of</strong> detecting bovine paratuberculosis by sampling slaughtered cattle
which are macroscopically suspicious and unsuspicious for granulomatous enteritis.
Materials and Methods: The survey was subdivided into two studies in german slaughterhouses. In
study 1 sampling was done on 50 cattle with macroscopic lesions <strong>of</strong> granulomatous enteritis (thickening <strong>of</strong>
<strong>the</strong> intestinal wall, gyrus form mucosa folds, granular appearance <strong>of</strong> <strong>the</strong> intestinal mucosa, dilated mesenteric
lymphatics). In study 2 sampling was done on 150 cows which were not suspicious for granulomatous enteritis.
Samples for bacteriological, histopathological and immunohistochemical examinations were taken from ileum,
jejunum, Nll. mesenteriales and Nll. caecales.
Results: By sampling cattle with macroscopic lesions <strong>of</strong> granulomatous enteritis in study 1, 98% were
MAP-positive. The prevalence <strong>of</strong> macroscopic suspicious, MAP-positive cattle was 1.35% <strong>of</strong> all slaughtered
cattle. The lesions reflected mainly advanced stages <strong>of</strong> disease. Macroscopic alterations were most commonly
seen in <strong>the</strong> ileum. Thickening <strong>of</strong> <strong>the</strong> intestinal wall and gyrus form mucosa folds were most frequent findings. In
study 2, 28% <strong>of</strong> <strong>the</strong> 150 sampled cows were MAP-positive without any macroscopic lesion seen in <strong>the</strong> intestine.
Tissue culture turned out to be <strong>the</strong> most sensitive test. Histological examination and immunohistochemical
or AFB staining identified fewer cattle to be infected. This was most obvious in study 2, in which sampled
animals were in less advanced stages <strong>of</strong> disease. Immunohistochemical examination <strong>of</strong> <strong>the</strong> tissue was more
sensitive <strong>the</strong>n Ziehl-Neelsen staining. Ileum and Nll. mesenteriales can be especially recommended as sampling
sites in cattle.
Conclusion: This study shows that a reliable detection <strong>of</strong> MAP-infected cattle is possible when macroscopic
lesions <strong>of</strong> granulomatous enteritis are evident. In prevalence studies on <strong>the</strong> basis <strong>of</strong> slaughterhouse
inspections it is necessary to examine cattle.
#151 Explaining persistence <strong>of</strong> Mycobacterium avium subsp. paratuberculosis in dairy herds
Rebecca Mans Mitchell, Graham F Medley, Ynte H Schukken
College <strong>of</strong> Veterinary Medicine, Cornell University, USA; Department <strong>of</strong> Biological Sciences, University <strong>of</strong> Warwick,
United Kingdom
In this work, we use a ma<strong>the</strong>matical model to illustrate MAP transmission dynamics on dairy farms. Following
<strong>the</strong> results <strong>of</strong> recent analysis <strong>of</strong> age-and-dose dependent shedding <strong>of</strong> MAP, we are able to build a model incorporating
true values <strong>of</strong> exit from each infectious category. The model is evaluated with and without an environmental
reservoir. This reservoir allows <strong>the</strong> infectious contribution from animals which have already exited <strong>the</strong>
population to decay over time.
We show <strong>the</strong> influence <strong>of</strong> changing assumptions concerning environmental persistence and supershedder
adult animals as well as <strong>the</strong> relative importance <strong>of</strong> calf-to-calf transmission. We find that
environmental loading could be a contributing factor allowing persistence <strong>of</strong> MAP on farms, and that calf-tocalf
transmission is necessary to produce a spectrum <strong>of</strong> prevalence observed worldwide. The presence <strong>of</strong>
age- and dose-dependent shedding <strong>of</strong> MAP among calves creates a bistable prevalence <strong>of</strong> infection following
intervention.
183