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A new compartmental model of Mycobacterium avium subsp. paratuberculosis infection dynamics in cattle

Smith, Rebecca L., Schukken, Ynte H., Gröhn, Yrjö T.
Preventive veterinary medicine 2015 v.122 no.3 pp. 298-305
Mycobacterium avium subsp. paratuberculosis, adults, calves, dairy farming, dairy herds, models, pathogens
Models of Mycobacterium avium subsp. paratuberculosis (MAP), a chronic infectious agent of cattle, are used to identify effective control programs. However, new biological findings show that adult infections occur and that infected animals can be separated into 2 paths: animals that will become high-shedding and, eventually, experience clinical disease (high-path); and animals that will shed only small quantities of MAP and will remain subclinical (low-path). Longitudinal data analysis found that high-path animals progress more quickly than previously believed. A standard model of MAP transmission in dairy herds was modified to include adult low-path infections and 2 infection pathways for infected calves. Analysis of this model showed that adult infection may play an important role in MAP dynamics on a dairy farm, and that the increased rate of progression for high-path animals influences both the prevalence and the persistence of MAP on a dairy farm. This new model will be able to determine the effectiveness of MAP control programs more accurately than previous models.