Assessment of the demographics and network structure of swine populations in relation to regional disease transmission and contro.

Abstract

Commercial swine production has steadily evolved the into interconnected multi-site production systems of today. As a result, large numbers of growing pigs and breeding animals move from one location to another on a daily basis. The health of the national swine herd has improved dramatically, due in large part to this new production structure; but the increased network size and the long distances travelled pose obvious threats to swine health. As animal agriculture has become more sophisticated, our government resources have not kept up. Available datasets are inaccurate, fragmented, and offer limited definition of the population at risk and its nature. National efforts to improve livestock population data have met considerable public resistance, and as a result, progress has been limited. Knowledge of the populations at risk is of primary importance when trying to define the potential for disease to spread within and between these populations. Disease spreads by non-mechanical means (as in aerosol transmission of PRRS virus) potentiates the need for knowledge of the neighborhood. Given the dynamic and transient nature of our swine populations, the neighborhood's health status is constantly challenged by the most recent delivery of pigs into the neighborhood. The following dissertation seeks to expand the knowledge of swine populations. Current geographic datasets were assessed for accuracy and reliability. In the event of a foreign animal disease outbreak the usefulness of these datasets would be of prime importance, as they will dictate the distribution of resources. Additionally, the use of satellite-derived thermal imagery to verify the presence of commercial swine is described, along with its estimated sensitivity and specificity. Any regional disease elimination program must consider all swine populations, therefore non-commercial populations (specifically, 4H exhibition pigs) are analyzed. Population size, seasonality, caretaker knowledge, presumed and measured health status, and relationship with commercial swine are defined. The physical movement of infected animals across the landscape allows rapid spread of a pathogen to occur. Volume, frequency, and geographic scale of movements will dictate how quickly and thoroughly an epidemic will proceed. For this reason, these are defined and displayed for pig producing areas at different scales.