Host factors affecting seroprevalence of bluetongue virus infections of cattle.
Results of testing of 19,731 samples from a serologic survey of cattle with bluetongue virus (BTV) infections in Australia were analyzed for association between age, species, or sex and test result. Bivariate analysis indicated that all 3 host factors were associated with test result. After adjusting for confounding caused by the location of each animal in the study (high, moderate, and low BTV prevalence regions), cattle > or = 4 years old had an odds ratio of 4.33 (95% confidence interval, 3.99, 4.71) for a positive test result, compared with that for cattle < 2 years old. Cattle 2 to 4 years had an odds ratio of 2.28 (2.14, 2.54), compared with cattle < 2 years old. Bos taurus cattle had an odds ratio of 1.76 (1.63, 2.05) of a positive test result, compared with crossbred cattle, and B indicus cattle had an odds ratio of 1.20 (1.09, 1.33), compared with crossbred cattle. Sexually intact (+) male cattle were found to have an odds ratio of 3.13 (2.66, 3.49) for a positive test result, compared with castrated male (-) cattle, and female cattle were found to have an odds ratio of 1.38 (1.29, 1.48), compared with male (-) cattle. Multivariate analysis of BTV testing results was performed, using stepwise logistic regression. The most parsimonious model selected included age, species, and sex factors, and first-order interaction terms between these factors. This model was only able to be fit to data from cattle restricted to the high (> 25%) BTV prevalence region. Odds ratio were found to increase with age for male (-) cattle of all species.(ABSTRACT TRUNCATED AT 250 WORDS)
Ward
M P
MP
Department of Medicine, School of Veterinary Medicine, University of California, Davis 95616.
Carpenter
T E
TE
Osburn
B I
BI
D000375:Aging; D000704:Analysis of Variance; D000818:Animals; D001315:Australia / Q000453:epidemiology; D001819:Bluetongue / Q000453:epidemiology*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology*; D005260:Female; D008297:Male; D015233:Models, Statistical; D016017:Odds Ratio; D013045:Species Specificity