Modeling of Mycobacterium avium subsp paratuberculosis dynamics in a dairy herd: An individual based approach
Authored by Mohammad A Al-Mamun, Rebecca L Smith, Ynte H Schukken, Yrjo T Grohn
Date Published: 2016
DOI: 10.1016/j.jtbi.2016.08.014
Sponsors:
United States Department of Agriculture (USDA)
Platforms:
No platforms listed
Model Documentation:
Other Narrative
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Mathematical description
Model Code URLs:
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Abstract
In the dairy industry, Johne's disease (JD), caused by Mycobacterium
avium subsp. paratuberculosis (MAP) is one of the major investigated
diseases. To date, researchers have suggested some control strategies
for JD, such as test-and-cull based herd management, isolated calf
rearing management, and vaccinations. Due to the slow progressing nature
of MAP, tests with low diagnostic test sensitivity and specificity, and
economic limitations, implementing these strategies has not resulted in
elimination of MAP from farms. To date, no study has integrated detailed
dairy herd dynamics with different MAP transmission routes. We have
developed an individual-based dairy herd model by incorporating basic
herd dynamics in a closed herd environment where no new animals have
been bought from outside. The model considered three age groups of
animals: calves, heifers and adults. It includes sequential life events
of a dairy animal and such key dynamic processes of the dairy herd as
lactation cycle, calving, voluntary waiting period, insemination, pregnancy, dry-off period and calf and heifer rearing. After initially
validating that the model reproduced typical herd dynamics, it was
extended by incorporating MAP infection dynamics, where each individual
adult animal belonged to one of four infection compartments:
susceptible, latent, low shedding and high shedding. The model includes
two disease transmission routes: horizontal transmission (i.e., fecal-oral) and vertical transmission (i.e., in utero infection). The
results confirm that this model can simulate a realistic dairy herd and
that inclusion of the above-mentioned dynamic processes provides useful
information about individual infected animals to farmers. Access to the
individual animal information offers more validity to assessment of
appropriate control strategies for an endemically MAP infected herd.
This model can serve as an accurate and novel tool not only to better
understand MAP dynamics, but is also valuable as an individual based
system of a typical dairy herd that can be applied to other research
questions. (C) 2016 Elsevier Ltd. All rights reserved.
Tags
cattle
compartmental model
United-states
Simulation-model
Cows
Risk-factors
Johnes-disease control
Control program
Management-practices
Milk-production