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)