Regional seroprevalence of bluetongue virus in cattle in Illinois and western Indiana.
OBJECTIVE
To estimate seroprevalence of bluetongue virus (BTV) and the geographic distribution of seropositive cattle herds in Illinois and western Indiana.


METHODS
10,585 serum samples obtained from cattle in 60 herds during 3 transmission seasons (2000 through 2002).


METHODS
In a longitudinal study, serum samples were tested for BTV antibodies by use of a competitive ELISA. Four geographic zones were created by use of mean minimum January temperature. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone, age of cattle, herd type, and transmission season.


RESULTS
Overall, BTV antibodies were detected in 156 (1.5%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 1.49%, 0.97%, and 2.18%, respectively. Risk of being seropositive for BTV was associated with geographic zone and age. Seroprevalence increased progressively from northern to southern zones, with no evidence of BTV infection in the northernmost zone. In the southernmost zone, annual seroprevalence ranged from 8.65% to 11.00%. Adult cattle were 2.35 times as likely as juvenile cattle to be seropositive.


CONCLUSIONS
Overall seroprevalence was lower than has been reported for Illinois cattle. Bluetongue virus antibodies were distributed heterogeneously in this region. Only in the southernmost zone was seroprevalence consistently > 2%. Regionalization of BTV risk based on state borders does not account for such variability. Serologic data could be combined with landscape, climate, and vector data to develop predictive models of BTV risk within transitional regions of the United States.
Boyer
Tim C
TC
Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108, USA.
Ward
Michael P
MP
Wallace
Richard L
RL
Singer
Randall S
RS
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001819:Bluetongue / Q000453:epidemiology* / Q000821:virology; D001820:Bluetongue virus / Q000302:isolation & purification*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000821:virology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D007087:Illinois / Q000453:epidemiology; D007196:Indiana / Q000453:epidemiology; D008137:Longitudinal Studies; D016036:Seroepidemiologic Studies
D000914:Antibodies, Viral