Objective—To assess fecal and nasal shedding patterns
of bovine torovirus (BoTV) in cattle at time of
arrival and periodically throughout the first 21 days
after arrival at a feedlot.
Procedure—Fecal and nasal-swab samples collected
on days 0, 4, 14, and 21 after arrival were tested for
BoTV, using ELISA. A subset of samples from calves
testing positive and negative for BoTV was analyzed,
using reverse transcriptase-polymerase chain reaction
(RT-PCR). Paired serum samples were collected on
days 0 and 21 and tested for BoTV antibodies, using
a hemagglutination inhibition assay.
Results—Overall rate of fecal shedding of BoTV was
21 of 57 (37%) by ELISA and 40 of 42 (95%) by
RT-PCR with peak shedding on day 4. Diarrhea was
more common in calves shedding BoTV than those
not shedding the virus (odds ratio, 1.72). Overall rate
of nasal shedding of BoTV was 15 of 57 (26%) by
ELISA and 42 of 42 (100%) by RT-PCR, with peak
shedding on day 0. Specificity of the RT-PCR product
was confirmed by sequence analysis. Approximately
93% of the calves seroconverted to BoTV (> 4-fold
increase in titer). Differences were not detected
between calves shedding BoTV and nonshedders in
relation to disease and treatments, perhaps because
of the low number of cattle in the study.
Conclusions and Clinical Relevance—This study
confirmed BoTV infections in feedlot cattle, including
BoTV antigen and viral RNA in nasal secretions, and
the shedding pattern during the first 21 days after
arrival in a feedlot. (Am J Vet Res 2002;63:342–348).