Table 1. Brief description of model variables.

Variable	Epidemiological description
S	Susceptible cattle. Cattle that have not yet picked up MAP bacteria
E	Exposed cattle (silent stage). Cattle with MAP but which cannot shed the bacilli to the environment or transmit infection to other cattle
Is	Subclinical cattle. Asymptomatic low-shedding but infectious cattle
I c	Clinical cattle. Asymptomatic and high-shedding cattle
N	Total cattle population
B	Environmental contamination through shedding from subclinical and clinical cattle