Herd factors affecting the selection and success of intervention strategies in the program for eradication of pseudorabies (Aujeszky's disease) virusfrom Illinois swine farms
Am. Siegel et Rm. Weigel, Herd factors affecting the selection and success of intervention strategies in the program for eradication of pseudorabies (Aujeszky's disease) virusfrom Illinois swine farms, PREV VET M, 40(3-4), 1999, pp. 243-259
The program for eradication of pseudorabies virus (PrV) from swine herds in
Illinois was evaluated with respect to compliance with Livestock Conservat
ion Institute (LCI) guidelines for selection of intervention strategies and
for the effectiveness of these interventions under different herd conditio
ns. The sample consisted of 395 swine operations quarantined between 1988 a
nd 1994. These herds were followed until the end of 1996. The association o
f herd characteristics (number of sows, sow PrV seroprevalence, type of hou
sing, number of PrV-seropositive farms within 1.5 mi) at the time of quaran
tine with the producer's selection of an initial intervention strategy (vac
cination, offspring segregation, test-and-removal, depopulation-and-repopul
ation) was analyzed using logistic multiple regression. The interaction of
herd characteristics with intervention strategies to affect the duration of
quarantine was analyzed using multivariable Cox regression.
Factors favoring selection of vaccination were increased herd size, higher
sow PrV seroprevalence, and more PrV-seropositive farms within 1.5 mi, Offs
pring segregation was preferred when sow PrV seroprevalence was higher, and
test-and-removal was preferred when seroprevalence was lower. Depopulation
-and-repopulation was more likely in outdoor operations. Except for depopul
ation-and-repopulation, selection of an intervention strategy was in accord
ance with LCI guidelines.
Vaccination and offspring segregation were associated with longer times und
er quarantine, and test-and-removal and depopulation-and-repopulation with
shorter times. Test-and-removal was more effective in reducing the duration
of quarantine when sow PrV seroprevalence was low. Vaccination increased t
he duration of quarantine less when sow PrV seroprevalence was high. Vaccin
ation increased the duration of quarantine more when there were one or more
PrV-seropositive farms within 1.5 mi than when there were no PrV-seroposit
ive farms within 1.5 mi. It is apparent that herd characteristics affect th
e duration of quarantine and therefore need to be taken into account in the
selection of a PrV-intervention strategy. (C) 1999 Elsevier Science B.V. A
ll rights reserved.