Within-herd transmission of paratuberculosis and the possible role of infectious calves

TL;DRAbstract

This study shows the results of an analysis of infection data of 21 Dutch dairy farms, where during 10 years each culled animal was tested for the presence of Mycobacterium avium subsp. paratuberculosis (Map). Twenty of the farms were part of a vaccination study. By allocating animals of the herd according to the S-L-I concept (Susceptible, Latently infected and Infectious), the transmission parameter β of the infection was estimated by generalised linear modelling. This parameter β is the average number of new infections caused by one initial infection per unit of time. Through β, the reproduction ratio R0 can be derived. The effect of management on the farm, time since start of vaccination, and several assumptions about the infectious period, were studied. The present analysis indeed showed that management had a significant effect on β and R0, and the advised hygienic measures decreased the within-herd transmission on these 21 farms. Furthermore, the transmission decreased significan

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