Objective—To determine the association between
the existence of a calf persistently infected (PI) with
bovine viral diarrhea virus (BVDV) and pen morbidity.
Animals—5,041 calves in 50 pens at a feedlot in
Procedure—In a longitudinal study, ear notches were
collected from cattle and tested for BVDV antigen.
Characteristics of each pen (owner, sex, disease rate,
number of groups, and source) were recorded. The
association between the existence of a BVDV–PI calf
and morbidity in each pen was examined.
Results—Commingling was associated with an
increase in respiratory tract disease (odds ratio [OR],
3; 95% confidence interval [CI], 2.5 to 3.6). Ten
BVDV–PI calves (10/5,041 [0.2%]) were identified in 8
of 50 pens. A BVDV–PI calf was associated with
reduced pen-level respiratory tract disease (OR, 0.7;
95% CI, 0.5 to 0.9). Disease prevalence (mean ± SD
morbidity, 7.9 ± 3.1%) was lowest in pens containing
single-source cattle and a BVDV–PI calf (4 pens containing
302 cattle), compared with single-source cattle
with no BVDV–PI calf (mean morbidity, 11.89 ±
9.7%; 31 pens containing 3,093 cattle), commingled
cattle with no BVDV–PI calf (mean morbidity, 29.3 ±
16.22%; 11 pens containing 1,127 cattle), and commingled
cattle with a BVDV–PI calf (mean morbidity,
28.6 ± 10.1%; 4 pens containing 519 cattle).
Conclusions and Clinical Relevance—Commingling
was the greatest risk factor associated with morbidity
in each pen. A BVDV–PI calf in a pen was not associated
with increased disease prevalence in commingled
groups. (Am J Vet Res 2005;66:2130–2134)
Objective−To report the prevalence of bovine viral diarrhea virus (BVDV) in calves and calf groups (ie, calves from the same farm) in beef breeding herds and evaluate the ability of biosecurity risk assessment questionnaires to identify calf groups with positive results for BVDV.
Animals−12,030 calves born in spring from 102 operations.
Procedures−Cow-calf producers that voluntarily enrolled in a screening project submitted ear notch specimens from calves and answered a 29-question survey instrument. Ear notch specimens were tested for BVDV with an antigen-capture ELISA (ACE), and ear notch specimens with positive ACE results for BVDV were immediately retested by performing immunohistochemistry (IHC). Follow-up testing, 3 to 4 weeks after initial positive ACE results, was done by use of a second IHC test and virus isolation on a subsequently submitted ear notch specimen from the same calves to identify those that were persistently infected (PI).
Results−102 producers submitted ear notch specimens for BVDV screening. Initially, 24 of 12,030 calves had positive ACE results for BVDV. A second ear notch specimen was submitted for 20 of these 24 calves. Of 20 retested calves, 12 had positive ICH results for BVDV, confirming PI status. The 12 PI calves came from 4 calf groups (3 singletons and 1 calf group with 9 PI calves).
Conclusions and Clinical Relevance−Prevalence of BVDV in calf groups was low, and questions designed to identify high-risk biosecurity behaviors had little value in identifying calf groups with positive results for BVDV.