Control measures to prevent the increase of paratuberculosis prevalence in dairy cattle herds: an individual-based modelling approach

Guillaume Camanes,Christine Fourichon,Pauline Ezanno,Racem Ben Romdhane,Alain Joly

doi:10.1186/s13567-018-0557-3

Guillaume Camanes, Christine Fourichon + Show 3 more

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https://doi.org/10.1186/s13567-018-0557-3

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Abstract

Paratuberculosis, a gastrointestinal disease caused by Mycobacterium avium subsp. paratuberculosis (Map), can lead to severe economic losses in dairy cattle farms. Current measures are aimed at controlling prevalence in infected herds, but are not fully effective. Our objective was to determine the most effective control measures to prevent an increase in adult prevalence in infected herds. We developed a new individual-based model coupling population and infection dynamics. Animals are characterized by their age (6 groups) and health state (6 states). The model accounted for all transmission routes and two control measures used in the field, namely reduced calf exposure to adult faeces and test-and-cull. We defined three herd statuses (low, moderate, and high) based on realistic prevalence ranges observed in French dairy cattle herds. We showed that the most relevant control measures depend on prevalence. Calf management and test-and-cull both were required to maximize the probability of stabilizing herd status. A reduced calf exposure was confirmed to be the most influential measure, followed by test frequency and the proportion of infected animals that were detected and culled. Culling of detected high shedders could be delayed for up to 3 months without impacting prevalence. Management of low prevalence herds is a priority since the probability of status stabilization is high after implementing prioritized measures. On the contrary, an increase in prevalence was particularly difficult to prevent in moderate prevalence herds, and was only feasible in high prevalence herds if the level of control was high.

Highlights

Paratuberculosis, a gastrointestinal infection commonly reported in cattle, is an incurable disease caused by Mycobacterium avium subsp. paratuberculosis (Map), a pathogen highly resistant in the environment [1, 2]
Probability of non‐degrading herd status The scenario involving the maximum control effort in this study was defined by a calf exposure to cow environment almost divided by 3, a test performed on cows every year, culling half of the moderately positive animals at most 6 months after infection, culling all highly positive animals at most 1 month after infection, and a removal rate of 80% for marked calves born to dams detected as highly positive during the calves’ first 10 weeks of life
Implication of main findings Our new individual-based model renders it possible to account for the heterogeneity of within-herd prevalence among infected herds when implementing control measures in dairy cattle herds

Summary

Introduction

Paratuberculosis, a gastrointestinal infection commonly reported in cattle, is an incurable disease caused by Mycobacterium avium subsp. paratuberculosis (Map), a pathogen highly resistant in the environment [1, 2]. Paratuberculosis, a gastrointestinal infection commonly reported in cattle, is an incurable disease caused by Mycobacterium avium subsp. Paratuberculosis (Map), a pathogen highly resistant in the environment [1, 2]. Multiple transmission routes are involved in the infection process, mainly during the first months of life [3, 4]. The second is horizontal, resulting from the ingestion of contaminated milk or colostrum, or after the ingestion of contaminated faeces from adults or from other calves [3, 6, 7]. Paratuberculosis presents a slow evolution in various infection stages, which display heterogeneous shedding patterns [8,9,10]. Visible clinical signs may occur, such as profuse diarrhoea, emaciation, decreased milk

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