Objective—To evaluate the use of systemic disease
signs for classifying severity of acute coliform mastitis
in dairy cows.
Design—Prospective cohort study.
Animals—144 dairy cows.
Procedure—Cows were examined at the time of initial
identification of disease (time 0) and classified as having
mild, moderate, or severe disease on the basis of
rectal temperature, hydration status, rumen contraction
rate, and attitude. A CBC and serum biochemical
analyses were performed, and milk samples were submitted
for bacterial culture at time 0 and 48 hours later.
Results—69 cows were classified as having mild disease,
44 as having moderate disease, and 31 as having
severe disease. Median WBC and neutrophil
counts were significantly lower in cows with moderate
or severe disease at time 0 than in cows with mild
disease. Band neutrophil count was significantly higher
at 48 hours and serum calcium concentration was
significantly lower at time 0 and at 48 hours in cows
with severe or moderate disease, compared with
cows with mild disease. Twenty-eight, 51, and 77% of
cows with mild, moderate, and severe disease,
respectively, had > 100,000 colony-forming units/ml
of milk at time 0. The odds that a cow with severe disease
would die or be culled were 3.6 times the odds
for a cow with moderate disease and 11.2 times the
odds for a cow with mild disease.
Conclusions and Clinical Relevance—Results suggest
that a classification scheme based on readily
observable systemic disease signs can be used to
classify disease severity in cows with acute coliform
mastitis. (J Am Vet Med Assoc 2001;218:567–572)
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)
Objective—To monitor ovine herpesvirus type 2
(OvHV-2) infection status and the association
between OvHV-2 infection and development of clinical
signs of malignant catarrhal fever (MCF) in cattle.
Animals—30 mature adult cows and 18 cattle submitted
Procedure—Blood and milk samples were collected at
monthly intervals from 30 adult cows for 20 consecutive
months. Nasal and ocular swab specimens were also
collected during months 9 through 20. Polymerase chain
reaction (PCR) assay for detection of OvHV-2 was performed
on blood, milk, nasal swab, and ocular swab
specimens. Competitive inhibition ELISA (CI-ELISA) for
detection of antibodies against MCF viruses was performed
on serum samples obtained prior to study initiation
and monthly during the last 12 months. Tissues
obtained from herdmates without clinical signs of MCF
that were submitted for necropsy were analyzed for
OvHV-2 DNA via PCR assay for possible sites of latency.
Results—Initially, 8 of 30 cows had positive CI-ELISA
results. Seroconversion was detected in 4 cows. Ovine
herpesvirus type 2 DNA was intermittently detected in
blood, milk, nasal secretions, or ocular secretions from
17 of 30 cows. Twenty-one cows had positive CI-ELISA
or PCR assay results. No cattle in the study developed
clinical signs of MCF. Results of PCR assays performed
on tissue samples from 2 of 18 animals submitted for
necropsy were positive for OvHV-2.
Conclusions and Clinical Relevance—OvHV-2 infection
can occur in cattle without concurrent development
of clinical MCF. Ovine herpesvirus type 2 DNA
was detected intermittently, suggesting fluctuating
viral DNA loads or reinfection in subclinical cattle. A
definitive site of latency was not identified from tissues
obtained during necropsy. (J Am Vet Med Assoc
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