Abstract
The role of transportation vehicles, pig movement between farms, proximity to
infected premises, and feed deliveries has not been fully considered in the
dissemination dynamics of porcine epidemic diarrhea virus (PEDV). This has
limited efforts for disease control and elimination restricting the development
of risk-based resource allocation to the most relevant modes of PEDV
dissemination. Here, we modeled nine modes of between-farm transmission
pathways including farm-to-farm proximity (local transmission), contact network
of pig farm movements between sites, four different contact networks of
transportation vehicles (vehicles that transport pigs from farm-to-farm, pigs
to markets, feed distribution and crew), the volume of animal by-products
within feed diets (e.g. animal fat and meat and bone meal) to reproduce PEDV
transmission dynamics. The model was calibrated in space and time with weekly
PEDV outbreaks. We investigated the model performance to identify outbreak
locations and the contribution of each route in the dissemination of PEDV. The
model estimated that 42.7% of the infections in sow farms were related to
vehicles transporting feed, 34.5% of infected nurseries were associated with
vehicles transporting pigs to farms, and for both farm types, pig movements or
local transmission were the next most relevant routes. On the other hand,
finishers were most often (31.4%) infected via local transmission, followed by
the vehicles transporting feed and pigs to farm networks. Feed ingredients did
not significantly improve model calibration metrics. The proposed modeling
framework provides an evaluation of PEDV transmission dynamics, ranking the
most important routes of PEDV dissemination and granting the swine industry
valuable information to focus efforts and resources on the most important
transmission routes.