Objective—To determine whether the stress of an
ultrasonographic procedure would interfere with the
suppressive effect of dexamethasone during a lowdose
dexamethasone suppression test (LDDST) in
Animals—6 clinically normal adult dogs.
Procedure—In phase 1, an LDDST was performed 5
times at weekly intervals in each dog. Serum samples
were obtained 0, 2, 4, 6, and 8 hours after dexamethasone
injection. A mock 20-minute abdominal ultrasonographic
examination was performed on all dogs at each
time point during the LDDST on weeks 2 through 5. In
phase 2, serum cortisol concentrations were measured
before and immediately after a 20-minute mock
abdominal ultrasonographic examination, as described
for phase 1.
Results—We did not detect significant differences
after dexamethasone injection when comparing
median cortisol concentrations for weeks 2 to 5
(mock ultrasonographic procedure) with median concentration
for week 1 (no mock ultrasonographic procedure).
For 5 of the 6 dogs, cortisol concentrations
after dexamethasone injection decreased to < 35.9
nmol/L after each mock ultrasonographic procedure
and remained low for the duration of the LDDST. In
phase 2, all dogs had significant increases in cortisol
concentrations immediately after the mock ultrasonographic
Conclusions and Clinical Relevance—A 20-minute
mock abdominal ultrasonographic examination performed
during LDDST did not alter results of the
LDDST in most dogs. Cortisol concentrations measured
immediately after a mock ultrasonographic
examination were significantly increased. Ultrasonographic
procedures should be performed a minimum
of 2 hours before collection of samples that will
be used to measure cortisol concentrations. ( Am J Vet Res 2004;65:267–270)
OBJECTIVE To identify clinical or clinicopathologic variables that can be used to predict a positive PCR assay result for Anaplasma phagocytophilum infection in equids.
ANIMALS 162 equids.
PROCEDURES Medical records were reviewed to identify equids that underwent testing for evidence of A phagocytophilum infection by PCR assay between June 1, 2007, and December 31, 2015. For each equid that tested positive (case equid), 2 time-matched equids that tested negative for the organism (control equids) were identified. Data collected included age, sex, breed, geographic location (residence at the time of testing), physical examination findings, and CBC and plasma biochemical analysis results. Potential predictor variables were analyzed by stepwise logistic regression followed by classification and regression tree analysis. Generalized additive models were used to evaluate identified predictors of a positive test result for A phagocytophilum.
RESULTS Total lymphocyte count, plasma total bilirubin concentration, plasma sodium concentration, and geographic latitude were linear predictors of a positive PCR assay result for A phagocytophilum. Plasma creatine kinase activity was a nonlinear predictor of a positive result.
CONCLUSIONS AND CLINICAL RELEVANCE Assessment of predictors identified in this study may help veterinarians identify equids that could benefit from early treatment for anaplasmosis while definitive test results are pending. This information may also help to prevent unnecessary administration of oxytetracycline to equids that are unlikely to test positive for the disease.
Objective—To evaluate effects of trimethoprim-sulfamethoxazole
(T/SMX) on thyroid function in dogs.
Animals—6 healthy euthyroid dogs.
Procedure—Dogs were administered T/SMX (14.1 to
16 mg/kg, PO, q 12 h) for 3 weeks. Blood was collected
weekly for 6 weeks for determination of total
thyroxine (TT4), free thyroxine (fT4), and canine thyroid-
stimulating hormone (cTSH) concentrations.
Schirmer tear tests were performed weekly. Blood
was collected for CBC prior to antimicrobial treatment
and at 3 and 6 weeks.
Results—5 dogs had serum TT4 concentrations
equal to or less than the lower reference limit, and 4
dogs had serum fT4 less than the lower reference
limit after 3 weeks of T/SMX administration; cTSH
concentrations were greater than the upper reference
limit in 4 dogs. All dogs had TT4 and fT4 concentrations
greater than the lower reference limit
after T/SMX administration was discontinued for 1
week, and cTSH concentrations were less than reference
range after T/SMX administration was discontinued
for 2 weeks. Two dogs developed
decreased tear production, which returned to normal
after discontinuing administration.
Conclusions and Clinical Relevance—Results suggest
that administration of T/SMX at a dosage of 14.1 to
16 mg/kg, PO, every 12 hours for 3 weeks caused
decreased TT4 and fT4 concentrations and increased
cTSH concentration, conditions that would be compatible
with a diagnosis of hypothyroidism. Therefore, dogs
should not have thyroid function evaluated while receiving
this dosage of T/SMX for > 2 weeks. These results
are in contrast to those of a previous study of trimethoprim-
sulfadiazine. (Am J Vet Res 2005;66:256–259)
Objective—To determine the frequency of isolation and
susceptibility patterns of Staphylococcus schleiferi from
healthy dogs and dogs with otitis, pyoderma, or both
that had or had not received antimicrobial treatment.
Procedure—Dogs were allocated to 1 of 4 groups:
healthy dogs (n = 13), dogs without otitis but with pyoderma
(10), dogs with otitis but without pyoderma (11),
and dogs with otitis and pyoderma (16). Bacteriologic
culture of ear swab specimens was performed in all
dogs. Bacteriologic culture of skin swab specimens
was also performed in dogs with concurrent pyoderma.
Isolates were identified as S schleiferi subsp schleiferi
or S schleiferi subsp coagulanson the basis of growth
and biochemical characteristics.
Results—S schleiferi was not isolated from any dogs with
pyoderma only. Staphylococcus schleiferi subsp schleiferi
was isolated from the ears of 2 healthy dogs, and the skin
and ears of 2 dogs and the skin of 1 dog with otitis and
pyoderma. Staphylococcus schleiferi subsp coagulans
was isolated from the ears of 3 dogs with otitis only, and
the ears of 6 dogs and the skin of 2 dogs with otitis and
pyoderma. One of the S schleiferi subsp schleiferi isolates
from ears, 2 of the S schleiferi subsp coagulansisolates
from ears, and 1 of the S schleiferi subsp coagulansisolates
from the skin were resistant to methicillin. One
methicillin-resistant isolate from the ears and 1 from the
skin were also resistant to fluoroquinolones.
Conclusions and Clinical Relevance—S schleiferi
subsp schleiferiwas detected in healthy dogs and dogs
with otitis and pyoderma. Methicillin-resistant and -susceptible
S schleiferi subsp schleiferi and S schleiferi
subsp coagulans were detected as the predominant
organisms in dogs with otitis. ( J Am Vet Med Assoc 2005;227:928–931)
Objective—To compare the pharmacokinetics of
penicillin G and procaine in racehorses following IM
administration of penicillin G procaine (PGP) with
pharmacokinetics following IM administration of penicillin
G potassium and procaine hydrochloride (PH).
Animals—6 healthy adult mares.
Procedure—Horses were treated with PGP (22,000
units of penicillin G/kg of body weight, IM) and with
penicillin G potassium (22,000 U/kg, IM) and PH
(1.55 mg/kg, IM). A minimum of 3 weeks was allowed
to elapse between drug treatments. Plasma and urine
penicillin G and procaine concentrations were measured
by use of high-pressure liquid chromatography.
Results—Median elimination phase half-lives of penicillin
G were 24.7 and 12.9 hours, respectively, after
administration of PGP and penicillin G potassium.
Plasma penicillin G concentration 24 hours after administration
of penicillin G potassium and PH was not significantly
different from concentration 24 hours after
administration of PGP. Median elimination phase halflife
of procaine following administration of PGP (15.6
hours) was significantly longer than value obtained
after administration of penicillin G potassium and PH
Conclusions and Clinical Relevance—Results suggest
that IM administration of penicillin G potassium
will result in plasma penicillin G concentrations for 24
hours after drug administration comparable to those
obtained with administration of PGP. Clearance of procaine
from plasma following administration of penicillin
G potassium and PH was rapid, compared with clearance
following administration of PGP. (Am J Vet Res