Descriptive epidemiology of postnatal bovine viral diarrhea virus infection in intensively managed dairy heifers

Donald M. Rush Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.
Present address is 2416 West Lonsdale Blvd, Northfield, MN 55057.

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 DVM, MPVM
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Mark C. Thurmond Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Claudia A. Muñoz-Zanzi Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Sharon K. Hietala California Animal Health and Food Safety Laboratory, University of California, Davis, CA 95616.

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 PhD

Abstract

Objective—To evaluate risk of bovine viral diarrhea virus (BVDV) infection between birth and 9 months of age for dairy replacement heifers raised under typical dry-lot management conditions.

Design—Longitudinal observational study.

Animals—446 calves.

Procedure—Calves were randomly selected from 2 dairies that used killed and modified-live BVDV vaccines. Repeated serologic and BVDV polymerase chain reaction assays were used to estimate risk of BVDV infection in calves of various ages (1 to 60 days; 61 to 100 days; 101 days to 9 months) and to estimate overall infection rate by 9 months of age.

Results—Risk of BVDV infection increased with age (maximum risk, 150 to 260 days). Proportion of calves infected with BVDV by 9 months of age was higher for dairy A (0.665), compared with dairy B (0.357). Percentage infected with BVDV type I did not differ between dairy A (18.2%) and dairy B (15.2%), whereas percentage infected with BVDV type II for dairy A (50%) was twice that for dairy B (21%). Between 210 and 220 days of age, infection with BVDV regardless of type was > 1.3%/d on dairy A and 0.5%/d on dairy B.

Conclusions and Clinical Relevance—Under drylot conditions, a considerable amount of BVDV infection may occur before 9 months of age. Risk of infection increases with age. Although dairies may appear to have similar management practices, there can be considerably different risks of BVDV infection among dairies. (J Am Vet Med Assoc 2001;219:1426–1431)

Abstract

Objective—To evaluate risk of bovine viral diarrhea virus (BVDV) infection between birth and 9 months of age for dairy replacement heifers raised under typical dry-lot management conditions.

Design—Longitudinal observational study.

Animals—446 calves.

Procedure—Calves were randomly selected from 2 dairies that used killed and modified-live BVDV vaccines. Repeated serologic and BVDV polymerase chain reaction assays were used to estimate risk of BVDV infection in calves of various ages (1 to 60 days; 61 to 100 days; 101 days to 9 months) and to estimate overall infection rate by 9 months of age.

Results—Risk of BVDV infection increased with age (maximum risk, 150 to 260 days). Proportion of calves infected with BVDV by 9 months of age was higher for dairy A (0.665), compared with dairy B (0.357). Percentage infected with BVDV type I did not differ between dairy A (18.2%) and dairy B (15.2%), whereas percentage infected with BVDV type II for dairy A (50%) was twice that for dairy B (21%). Between 210 and 220 days of age, infection with BVDV regardless of type was > 1.3%/d on dairy A and 0.5%/d on dairy B.

Conclusions and Clinical Relevance—Under drylot conditions, a considerable amount of BVDV infection may occur before 9 months of age. Risk of infection increases with age. Although dairies may appear to have similar management practices, there can be considerably different risks of BVDV infection among dairies. (J Am Vet Med Assoc 2001;219:1426–1431)

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