Objective—To evaluate the effectiveness of various
sampling techniques for determining antimicrobial
resistance patterns in Escherichia coli isolated from
feces of feedlot cattle.
Sample Population—Fecal samples obtained from
328 beef steers and 6 feedlot pens in which the cattle
Procedure—Single fecal samples were collected
from the rectum of each steer and from floors of pens
in which the cattle resided. Fecal material from each
single sample was combined into pools containing 5
and 10 samples. Five isolates of Escherichia coli from
each single sample and each pooled sample were
tested for susceptibility to 17 antimicrobials.
Results—Patterns of antimicrobial resistance for
fecal samples obtained from the rectum of cattle did
not differ from fecal samples obtained from pen
floors. Resistance patterns from pooled samples differed
from patterns observed for single fecal samples.
Little pen-to-pen variation in resistance prevalence
was observed. Clustering of resistance phenotypes
within samples was detected.
Conclusions and Clinical Relevance—Studies of
antimicrobial resistance in feedlot cattle can rely on
fecal samples obtained from pen floors, thus avoiding
the cost and effort of obtaining fecal samples from the
rectum of cattle. Pooled fecal samples yielded resistance
patterns that were consistent with those of single
fecal samples when the prevalence of resistance
to an antimicrobial was > 2%. Pooling may be a practical
alternative when investigating patterns of resistance
that are not rare. Apparent clustering of resistance
phenotypes within samples argues for examining
fewer isolates per fecal sample and more fecal
samples per pen. (Am J Vet Res 2002;63:1662–1670)
Objective—To determine the prevalence, fecal shedding
pattern, and association of bovine torovirus
(BoTV) with diarrhea in veal calves at time of arrival
and periodically throughout the first 35 days after their
arrival on a veal farm.
Animals—62 veal calves.
Procedure—Fecal samples collected on days 0, 4, 14,
and 35 after arrival were tested for BoTV by use of
ELISA and reverse transcriptase-polymerase chain
reaction (RT-PCR) assay. Paired serum samples
obtained from blood collected on days 0 and 35 were
analyzed for BoTV antibodies with a hemagglutination
inhibition assay. Fecal samples were also screened
for other enteric pathogens, including rotavirus, coronavirus,
and Cryptosporidium spp.
Results—Fecal shedding of BoTV was detected in 15
of 62 (24%) calves by use of ELISA and RT-PCR assay,
with peak shedding on day 4. A significant independent
association between BoTV shedding and diarrhea
was observed. In addition, calves shedding ≥ 2
enteric pathogens were more likely to have diarrhea
than calves shedding ≤ 1 pathogen. Calves that were
seronegative or had low antibody titers against BoTV
(≤ 1:10 hemagglutination inhibition units) at arrival
seroconverted to BoTV (> 4-fold increase in titer);
these calves were more likely to shed virus than
calves that were seropositive against BoTV at arrival.
Conclusions and Clinical Relevance—Shedding of
BoTV was strongly associated with diarrhea in neonatal
veal calves during the first week after arrival at the
farm. These data provide evidence that BoTV is an
important pathogen of neonatal veal calves.
(Am J Vet Res 2003;64:485–490)
Case Description—A 2-year-old spayed female domestic shorthair cat was examined because of bilateral thoracic limb weakness of acute onset.
Clinical Findings—Clinical signs included muscle atrophy, paresis, depressed spinal reflexes, hyperesthesia of the thoracic limbs, and reduced jaw muscle tone. Pelvic limb reflexes were normal. Results of a neurologic examination were suggestive of multifocal lesions involving both brachial plexuses and the trigeminal nerves. Abnormal nerve conduction across the brachial plexus and delayed late potentials were found on electrodiagnostic testing, and diffuse subclinical involvement of other regions of the peripheral nervous system was confirmed on the basis of abnormal electromyographic findings for the masticatory muscles and conduction block of the peroneal nerve.
Treatment and Outcome—No specific treatments were given, and neurologic signs resolved within a month. A relapse occurred 2 months after the first episode, with clinical signs affecting both the pelvic and the thoracic limbs on this occasion. Again, the condition resolved without specific treatment, and 13 months after the initial episode, the cat reportedly was normal.
Conclusions and Clinical Relevance—Findings suggested that brachial plexus neuropathy can be a multifocal disease in cats, even if clinically apparent neurologic deficits are initially subtle or absent, and that electrodiagnostic techniques can be used to identify subclinical involvement of the peripheral nerves.
Objective—To evaluate various sampling strategies for potential use in measuring prevalence of antimicrobial susceptibility in cattle.
Sample Population—500 isolates of non–type-specific Escherichia coli (NTSEC) isolated from the feces of 50 cows from 2 dairy farms (25 cows/farm and 10 isolates/cow).
Procedures—Diameters of inhibition zones for 12 antimicrobials were analyzed to estimate variation among isolates, cows, and farms and then used to determine sampling distributions for a stochastic simulation model to evaluate 4 sampling strategies. These theoretic sampling strategies used a total of 100 isolates in 4 allocations (1 isolate from 100 cows, 2 isolates from 50 cows, 3 isolates from 33 cows, or 4 isolates from 25 cows).
Results—Analysis of variance composition revealed that 74.2% of variation was attributable to isolates, 18.5% to cows, and 7.3% to farms. Analysis of results of simulations suggested that when most of the variance was attributable to differences among isolates within a cow, culturing 1 isolate from each of 100 cows underestimated overall prevalence, compared with results for culturing more isolates per cow from fewer cows. When variance was not primarily attributable to differences among isolates, all 4 sampling strategies yielded similar results.
Conclusions and Clinical Relevance—It is not always possible to predict the hierarchical level at which clustering will have its greatest impact on observed susceptibility distributions. Results suggested that sampling strategies that use testing of 3 or 4 isolates/cow from a representative sample of all animals better characterize herd prevalence of antimicrobial resistance when impacted by clustering.
OBJECTIVE To assess the use of 3-D accelerometers to evaluate behavioral changes in cattle experimentally infected with a low-virulent strain of bovine viral diarrhea virus (BVDV).
ANIMALS 20 beef steers (mean weight, 238 kg).
PROCEDURES Calves were allocated to a BVDV (n = 10) or control (10) group. On day 0, calves in the BVDV group were inoculated with a low-virulent strain of BVDV (4 × 106 TCID50, intranasally), and calves in the control group were sham inoculated with BVDV-free medium (4 mL; intranasally). An accelerometer was affixed to the right hind limb of each calf on day −7 to record activity (lying, walking, and standing) continuously until 35 days after inoculation. Baseline was defined as days −7 to −1. Blood samples were collected at predetermined times for CBC, serum biochemical analysis, virus isolation, and determination of anti-BVDV antibody titers.
RESULTS All calves in the BVDV group developed viremia and anti-BVDV antibodies but developed only subclinical or mild disease. Calves in the control group did not develop viremia or anti-BVDV antibodies. Mean time allocated to each activity did not differ significantly between the BVDV and control groups on any day except day 8, when calves in the BVDV group spent less time standing than the calves in the control group. Following inoculation, calves in both groups tended to spend more time lying and less time walking and standing than they did during baseline.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that behavioral data obtained by accelerometers could not distinguish calves subclinically infected with BVDV from healthy control calves. However, subtle changes in the behavior of the BVDV-infected calves were detected and warrant further investigation.
Objective—To determine the effects of meloxicam on values of hematologic and plasma biochemical analysis variables and results of histologic examination of tissue specimens of Japanese quail (Coturnix japonica).
Animals—30 adult Japanese quail.
Procedures—15 quail underwent laparoscopic examination of the left kidneys, and 15 quail underwent laparoscopic examination and biopsy of the left kidneys. Quail in each of these groups received meloxicam (2.0 mg/kg, IM, q 12 h; n = 10) or a saline (0.9% NaCl) solution (0.05 mL, IM, q 12 h; control birds; 5) for 14 days. A CBC and plasma biochemical analyses were performed at the start of the study and within 3 hours after the last treatment. Birds were euthanized and necropsies were performed.
Results—No adverse effects of treatments were observed, and no significant changes in values of hematologic variables were detected during the study. Plasma uric acid concentrations and creatine kinase or aspartate aminotransferase activities were significantly different before versus after treatment for some groups of birds. Gross lesions identified during necropsy included lesions at renal biopsy sites and adjacent air sacs (attributed to the biopsy procedure) and pectoral muscle hemorrhage and discoloration (at sites of injection). Substantial histopathologic lesions were limited to pectoral muscle necrosis, and severity was greater for meloxicam-treated versus control birds.
Conclusions and Clinical Relevance—Meloxicam (2.0 mg/kg, IM, q 12 h for 14 days) did not cause substantial alterations in function of or histopathologic findings for the kidneys of Japanese quail but did induce muscle necrosis; repeated IM administration of meloxicam to quail may be contraindicated.
Objective—To determine the disposition of gamithromycin in plasma, pulmonary epithelial lining fluid (PELF), bronchoalveolar lavage (BAL) cells, and lung tissue homogenate in cattle.
Animals—33 healthy Angus calves approximately 7 to 8 months of age.
Procedures—Calves were randomly assigned to 1 of 11 groups consisting of 3 calves each, which differed with respect to sample collection times. In 10 groups, 1 dose of gamithromycin (6 mg/kg) was administered SC in the neck of each calf (0 hours). The remaining 3 calves were not treated. Gamithromycin concentrations in plasma, PELF, lung tissue homogenate, and BAL cells (matrix) were measured at various points by means of high-performance liquid chromatography with tandem mass spectrometry.
Results—Time to maximum gamithromycin concentration was achieved at 1 hour for plasma, 12 hours for lung tissue, and 24 hours for PELF and BAL cells. Maximum gamithromycin concentration was 27.8 μg/g, 17.8 μg/mL, 4.61 μg/mL, and 0.433 μg/mL in lung tissue, BAL cells, PELF, and plasma, respectively. Terminal half-life was longer in BAL cells (125.0 hours) than in lung tissue (93.0 hours), plasma (62.0 hours), and PELF (50.6 hours). The ratio of matrix to plasma concentrations ranged between 4.7 and 127 for PELF, 16 and 650 for lung tissue, and 3.2 and 2,135 for BAL cells.
Conclusions and Clinical Relevance—Gamithromycin was rapidly absorbed after SC administration. Potentially therapeutic concentrations were achieved in PELF, BAL cells, and lung tissue within 30 minutes after administration and persisted for 7 (PELF) to > 15 (BAL cells and lung tissue) days after administration of a single dose.
Objective—To measure antibody titers against
bovine coronavirus (BCV), determine frequency of
BCV in nasal swab specimens, and compare calves
treated for bovine respiratory tract disease (BRD)
between those given an intranasally administered
vaccine and control calves.
Design—Randomized clinical trial.
Animals—414 heifer calves.
Procedure—Intranasal BCV antigen concentration
and antibody titer against BCV were measured on
entry to a feedlot. Calves were randomly assigned to
receive 3.0 mL of a modified-live virus vaccine against
bovine enteric coronavirus and rotavirus or 3.0 mL of
saline (0.9% NaCl) solution. Calves were confined to
1 of 2 pens, depending on vaccination status, for a
minimum of 17 days of observation (range, 17 to 99).
Selection of calves for treatment of BRD and scoring
for severity of disease were done by veterinarians
unaware of treatment status.
Results—Intranasal BCV (125/407 [31%]) and serum
antibody titers ≥ 20 against BCV (246/396 [62%])
were identified in calves entering the feedlot.
Vaccination was associated with significant decrease
in risk of treatment for BRD; intranasal BCV on entry
to the feedlot was associated with increased risk of
treatment. Univariate analysis revealed that control
calves with intranasal BRD on entry to the feedlot and
those with antibody titer < 20 were significantly more
likely to be treated for BRD.
Conclusions and Clinical Relevance—These data
provide further evidence of an association between
BCV and respiratory tract disease in feedlot calves.
An intranasally administered vaccine appeared to
reduce risk of treatment for BRD. (J Am Vet Med
Objective—To investigate risk factors for development
of equine protozoal myeloencephalitis (EPM) in
Animals—251 horses admitted to The Ohio State
University Veterinary Teaching Hospital from 1992 to
Procedure—On the basis of clinical signs of neurologic
disease and detection of antibody to Sarcocystis
neurona or S neurona DNA in cerebrospinal fluid, a
diagnosis of EPM was made for 251 horses. Two contemporaneous
series of control horses were selected
from horses admitted to the hospital. One control
series (n = 225) consisted of horses with diseases of
the neurologic system other than EPM (neurologic
control horses), and the other consisted of 251 horses
admitted for reasons other than nervous system
diseases (nonneurologic control horses). Data were
obtained from hospital records and telephone conversations.
Risk factors associated with disease status
were analyzed, using multivariable logistic regression.
Results—Horses ranged from 1 day to 30 years old
(mean ± SD, 5.7 ± 5.2 years). Risk factors associated
with an increased risk of developing EPM included
age, season of admission, prior diagnosis of EPM on
the premises, opossums on premises, health events
prior to admission, and racing or showing as a primary
use. Factors associated with a reduced risk of
developing EPM included protection of feed from
wildlife and proximity of a creek or river to the premises
where the horse resided.
Conclusions and Clinical Relevance—Development
of EPM was associated with a number of management-related factors that can be altered to decrease
the risk for the disease. (J Am Vet Med Assoc