An Investigation of Risk Factors for the Spread of Pseudorabies (Aujeszky's Disease) in Illinois Swine Herds

208 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993.Two areas of the epidemiology of the spread of pseudorabies virus among swine herds were examined: a spatial analysis at two levels (the county level and the individual farm level) and a case-control study of pseudorabies virus (PRV) in Illinois swine herds.The spatial analysis of PRV at the county level in Illinois revealed that county PRV prevalence rates varied from 0 to 34.41%, with clustering of prevalence values among counties which shared a common border (Moran's I: z-score = 10.04; p = 0.00001). Second-order analysis of county PRV prevalence rates also showed clustering of county PRV prevalence rates to be present. Weighted multiple linear regression was used to examine the effect of three factors expected to account for variation in county PRV prevalence rates. County herd density, average herd size and regional PRV density, and their two and three way interaction terms accounted for 69% of the variance in county PRV prevalence rates. An analysis of point locations of swine herds in Henry county, Illinois, from January 1, 1986, through December 31, 1991, revealed that herds quarantined for PRV infection were clustered at a statistically significant level in the county beginning at a distance of 2.42 kilometers, as compared to the overall distribution of swine herds in the county. Also, it was found that the clustering of clinically affected PRV quarantined herds occurred at a much higher level than the clustering of all PRV quarantined herds.In the case-control study of 80 herds, four factors were found to be important in differentiating PRV quarantined herds from tested negative herds. Risk of PRV quarantine was lower for producers that transported their own hogs to market as opposed to producers who hired truckers for transport and for producers who had their own transport vehicle and cleaned it after off-site visits rather than for producers who did not clean their vehicle. Risk of PRV quarantine was higher for producers with total confinement facilities rather than for producers with pasture operations, and for producers living in a township with greater than one other PRV quarantined swine herd.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD