The Importance of Livestock Demography and Infrastructure in Driving Foot and Mouth Disease Dynamics

Abstract

Transboundary animal diseases, such as foot and mouth disease (FMD) pose a significant and ongoing threat to global food security. Such diseases can producearge, spatially complex outbreaks. Mathematical models are often used to understand the spatio-temporal dynamics and create response plans for possible disease introductions. Model assumptions regarding transmission behavior of premises and movement patterns ofivestock directly impact our understanding of the ecological drivers of outbreaks and how to best control them. Here, we investigate the impact that these assumptions have on model predictions of FMD outbreaks in the U.S. using models ofivestock shipment networks and disease spread. We explore the impact of changing assumptions about premises transmission behavior, both by including within-herd dynamics, and by accounting for premises type and increasing the accuracy of shipment predictions. We find that the impact these assumptions have on outbreak predictions isess than the impact of the underlyingivestock demography, but that they are important for investigating some response objectives, such as the impact on trade. These results suggest that demography is a key ecological driver of outbreaks and is critical for making robust predictions but that understanding management objectives is also important when making choices about model assumptions.

An exploration of within-herd dynamics of a transboundary livestock disease: A foot and mouth disease case study

“…The duration that individual herds contribute to transmission will also be important for understanding how the composition of premises contributes to the overall outbreak dynamics. Studies have shown that aspects of demography, including premises clustering, and the number of large farms in a given area, impact the outcome of potential FMD outbreaks (Werkman et al, 2016;Tsao et al, 2019;Gilbertson et al, 2022). Using well informed estimates for the duration of infectiousness for herds of different sizes will help disentangle the impact of herd size on duration of an outbreak within a herd versus the duration of an outbreak across multiple herds.…”

“…Assuming the entire herd or flock is a single unit is a simplifying assumption but it provides policy makers with metrics of interest about potential outbreaks, including the number of potential herds or flocks infected and the spatial extent. However, some outbreak metrics of interest to policy makers are influenced by within-herd dynamics, particularly overall outbreak duration (Chis Ster et al, 2012;Gilbertson et al, 2022), which is important for understanding potential economic impacts and can be underestimated by models that do not include within-herd dynamics.…”

Simulating contact networks for livestock disease epidemiology: a systematic review

“…Building on these, the USAMM model [25], which has been applied and modified extensively [76][77][78][79][80][81][82][83][84], uses a Bayesian kernel approach to reconstruct the US cattle trade network. Similarly to GMs, movement probabilities were modelled as a function of the number of cattle premises at the origin and destination, and the distance between them, while also incorporating data on historical state-level cattle inflows.…”

Laboratory testing and on-site storage are successful at mitigating the risk of release of foot-and-mouth disease virus via production of bull semen in the USA

“…Airborne transmission also remains possible, depending on the distance to neighboring barns and other farms. The annual probability of an FMD outbreak in a given facility (H), was modeled using an empirical distribution fitted to the data on predicted incidence of FMD outbreaks from five models [23][24][25][26][27]. More details about the estimates used are available in S1 Appendix.…”