A deterministic and stochastic simulation model for intra-herd paratuberculosis transmission

Abstract

-In France, the considerable economic losses due to paratuberculosis introduction in cattle herds may justify the development of a herd-level certification procedure. For a cost/benefit analysis purpose, a simple deterministic and stochastic simulation model for intra-herd paratuberculosis transmission has been developed to evaluate the economic consequences of the purchase of a single infected heifer in a French average herd. The values of the epidemiological parameters were provided by a panel of French paratuberculosis experts. The results were in adequacy with field observations. A sensitivity analysis was conducted. The model was however difficult to validate rigorously, since few data on the intra-herd paratuberculosis true prevalence level are currently available. paratuberculosis / stochastic model / deterministic model / sensitivity analysis

A cost/benefit study of paratuberculosis certification in French cattle herds

“…Despite the fact that, when the disease reaches a stable endemic state, the yearly incidence is predicted to be smaller in the mean beef herd than in the mean dairy herd [11], this difference was mainly due to the fact that, at the chosen time horizon (15 years), the disease had almost reached this endemic state in the mean dairy herd, whereas this was not the case in the mean beef herd, where the dynamics was predicted to be slower.…”

“…The epidemiological model used to generate the intra-herd paratuberculosis dynamics [11] was designed to simulate the disease progression from a single initial introduction of a single infected heifer. This is obviously not the only possible introduction modality: more than one infected heifer could be bought by the breeder, and/ or such an event could occur more than once.…”

“…Our study was restricted to a herdlevel analysis, and such a population-level effect could not be taken into account. The probability for a bought heifer to be infected would then decrease over time, and, as a consequence, the certification benefits would decrease.The epidemiological model used to generate the intra-herd paratuberculosis dynamics [11] was designed to simulate the disease progression from a single initial introduction of a single infected heifer. This is obviously not the only possible introduction modality: more than one infected heifer could be bought by the breeder, and/or such an event could occur more than once.…”

“…A deterministic simulation model [11] was designed to generate the average paratuberculosis dynamics in a cattle herd, assuming that a single infected heifer was introduced in the herd at the beginning of the simulated period.…”

“…The epidemiological model used to generate the disease dynamics [11] has two kinds of parameters: epidemiological parameters that control the simulated disease transmission, and herd management parameters, that control herd population dynamics. The values of the epidemiological parameters were provided by the working group, and the simulation results were also validated by this group.…”