Objective—To estimate seroprevalence of Mycobacterium
avium subsp paratuberculosis (MAP) infection
among adult dairy cows in Colorado and determine
herd-level factors associated with the risk that individual
cows would be seropositive.
Design—Cross-sectional observational study.
Animals—10,280 adult (≥ 2 years old) dairy cows in
15 herds in Colorado.
Procedure—Serum samples were tested with a commercial
ELISA. A herd was considered to be infected
with MAP if results of mycobacterial culture of ≥ 1
individual cow fecal sample were positive or if ≥ 1
culled cow had histologic evidence of MAP infection.
Results—424 of the 10,280 (4.12%) cows were
seropositive. Within-herd prevalence of seropositive
cows ranged from 0% to 7.82% (mean, 2.6%).
Infection was confirmed in 11 dairies. Cows in herds
that had imported ≥ 8% of their current herd size
annually during the preceding 5 years were 3.28
times as likely to be seropositive as were cows in
herds that imported < 8%. Cows in herds with ≥ 600
lactating cows were 3.12 times as likely to be
seropositive as were cows in herds with < 600 lactating
cows. Cows in herds with a history of clinical
signs of MAP infection were 2.27 times as likely to be
seropositive as were cows in herds without clinical
Conclusions and Clinical Relevance—Annual importation
rate, herd size, and whether cows in the herd
had clinical signs typical of MAP infection were associated
with the risk that individual cows would be
seropositive for MAP infection. (J Am Vet Med Assoc
Objective—To determine the incidence of bacteremia
in dairy cows with naturally occurring acute coliform
mastitis (ACM) with a wide range of disease severity.
Animals—144 dairy cows with ACM from 6 herds.
Procedure—Cows were examined at time of identification
of ACM (time 0) and classified as having mild,
moderate, or severe mastitis on the basis of rectal temperature,
hydration status, rumen contraction rate, and
attitude. Cows were reexamined at 24 or 48 hours.
Bacteriologic culturing of milk and blood (30 ml), CBC,
and serum biochemical analysis were performed at
each time point. Appropriate samples were obtained at
a single point from herdmates without mastitis (controls)
that were closely matched for lactation number
and days since parturition. Blood culture results were
compared among severity groups and controls by use
of χ2 tests, as was outcome of an ACM episode for
cows grouped by blood bacterial isolates.
Results—Bacteria were isolated from 52 blood samples
from 46 of 144 (32%) cows with ACM, which was significantly
more than control cows (11/156; 7.1%). Group-1
isolates (Escherichia coli, Pasteurella multocida,
Mannheimia haemolytica, Klebsiella pneumoniae,
Enterobacter agglomerans, and Salmonella enterica
serotype Typhimurium) were identified in 20 of 144 (14%)
cows with ACM and 0 of 156 control cows. Group-1 isolates
were identified in 4.3, 9.1, and 42% of cows classified
as having mild, moderate, and severe ACM, respectively.
Escherichia coli and K pneumoniae milk and blood
isolates obtained from the same cow were of the same
genotype. Bacillus spp were identified in 21 of 144 (15%)
cows with ACM, which was significantly more than control
cows (3/156; 1.9%). Thirty-five percent of cows with a
group-1 isolate died during the mastitis episode.
Conclusions and Clinical Relevance—Results suggest
that bacteremia develops in a substantial proportion
of cows with ACM. Classification of severity
of disease is important for establishment of effective
treatment protocols; parenteral antimicrobial treatment
may be indicated in cows with ACM. (J Am Vet
Med Assoc 2001;219:976–981)