Objective—To determine whether foals with pneumonia
that were treated with erythromycin, alone or
in combination with rifampin or gentamicin, had a
higher risk of developing adverse effects, compared
with foals treated with trimethoprim-sulfamethoxazole
(TMS), penicillin G procaine (PGP), or a combination
of TMS and PGP (control foals).
Animals—143 foals < 240 days old.
Procedure—Information on age, sex, breed, primary
drug treatment, total days of treatment with the primary
drug, and whether the foal developed diarrhea,
hyperthermia, or respiratory distress was obtained
from the medical records. Relative risk (RR) and attributable
risk (AR) were calculated to compare risk of
adverse reactions between foals treated with erythromycin
and control foals.
Results—Only 3 (4.3%) control foals developed diarrhea;
none developed hyperthermia or respiratory distress.
Foals treated with erythromycin had an 8-fold
risk (RR, 8.3) of developing diarrhea, compared with
control foals, and increased risks of hyperthermia
(AR, 25%) and respiratory distress (AR, 15%).
Conclusion and Clinical Relevance—Results suggest
that use of erythromycin to treat foals with pneumonia
was associated with an increased risk of diarrhea,
hyperthermia, and respiratory distress, compared
with use of TMS or PGP. (J Am Vet Med Assoc
Objective—To assess individual and combined associations of high-speed exercise and horseshoe characteristics with risk of forelimb proximal sesamoid bone fractures and proximal sesamoid bone midbody fractures in Thoroughbred racehorses.
Animals—269 deceased Thoroughbred racehorses.
Procedures—A case-control study design was used to compare 121 horses with a fracture of at least 1 of 4 forelimb proximal sesamoid bones (75 horses had a midbody fracture) and 148 horses without a forelimb proximal sesamoid bone fracture. Univariable and multivariable logistic regression analyses were used to evaluate potential risk factors for association with proximal sesamoid bone fracture.
Results—Compared with horses that died without proximal sesamoid bone fractures, horses that died with proximal sesamoid bone fractures were more likely to be sexually intact males, spend more time in active trainingand racing, complete more events, train and race longer since their last layup, have higher exercise intensities during the 12 months prior to death, and have greater cumulative distances for their career. Horses with proximal sesamoid bone midbody fractures were more likely to be sexually intact males, train and race longer since their last layup, and have higher exercise intensities during the 12 months prior to death.
Conclusions and Clinical Relevance—Limitingexercise intensity and the continuous time spent in activity duringa horse's career may decrease the frequency of forelimb proximal sesamoid bone fractures in Thoroughbred horses.
Objective—To evaluate flow cytometric analysis for
sex identification in 3 psittacine species, establish reference
values for blood cell DNA content for each
species, and determine effects of sample storage on
Animals—36 orange-winged Amazon parrots, 41
budgerigars, and 39 cockatiels.
Procedure—Blood samples were stained and analyzed
by use of flow cytometry to measure cellular
DNA content. Samples were analyzed immediately
after collection and after being stored at 4 C for 48
and 72 hours.
Results—Mean DNA content (picograms per cell)
was 3.248 for Amazon parrots, 2.702 for budgerigars,
and 2.946 for cockatiels; DNA concentrations in samples
analyzed immediately overlapped in a male and a
female Amazon parrot and among 19 cockatiels. For
budgerigars, DNA overlap between sexes was not
detected in samples analyzed immediately or after
storage for 72 hours. Sex was identified correctly in
94.4% of Amazon parrots, 100% of budgerigars, and
51.3% of cockatiels. For both sexes, DNA content in
samples analyzed immediately was significantly different
from that of stored samples.
Conclusions and Clinical Relevance—Flow cytometric
analysis was accurate for sex identification of
Amazon parrots and budgerigars. Sample storage at 4
C for 48 or 72 hours caused variability in DNA content.
(Am J Vet Res 2000;61:847–850)
Objective—To measure the frequency and magnitude of reduced fibrinogen binding in a population of horses from a Thoroughbred breeding farm.
Animals—444 Thoroughbred horses, 1 to 27 years old, including 316 females, 72 geldings, and 56 sexually intact males.
Procedures—Blood was collected from horses into tubes containingacid citrate dextrose adenine, and washed platelets were examined by use of flow cytometry for their ability to bind fibrinogen.
Results—Data regarding fibrinogen binding to activated platelets were normally distributed, with nearly identical amounts of variation regardless of sex. In 3 horses, fibrinogen binding to platelets was reduced from 67.6% to 83.4%, compared with normal platelets, which indicated an inability of platelets to aggregate in response to thrombin (0.1 U/mL).
Conclusions and Clinical Relevance—Platelet fibrinogen binding of the affected horses identified in this study was characteristic of a reported heritable bleeding disorder in which the reduction in fibrinogen binding correlated with prolonged bleeding times in template bleeding assays. The bleeding disorder is distinct from Glanzmann thrombasthenia, in which platelets fail to bind fibrinogen because of lack of αllb-β3 integrin on their surface. The prevalence of affected horses within the small sample population studied here (0.7% [n = 3]) is considerably higher than the prevalence of bleeding disorders within more genetically diverse groups.
Objective—To evaluate a Markov-chain model for the
development of forelimb injuries in Thoroughbreds
and to use the model to determine effects of reducing
sprint distance on incidence of metacarpal condylar
fracture (CDY) and severe suspensory apparatus
Sample Population—Weekly exercise and injury
data for 122 Thoroughbreds during racing or training.
Procedure—Weekly data were used to construct a
Markov-chain model with 5 states (uninjured [UNINJ],
palpable suspensory apparatus injury [PSAI], SSAI,
CDY, and lost to follow-up [LOST]). Transition probabilities
between UNINJ and PSAI were estimated as a
function of weekly sprint distance by use of linear
regression analysis. The model was used to predict
distributions of annual CDY and SSAI incidences in
southern California racehorses and was validated by
using CDY incidence reported by racetrack practitioners.
The model was modified by reducing the number
of sprint distances that were > 6 furlongs (> 1.20 km)
by 20%, and CDY and SSAI incidences were compared
with those generated by the baseline model.
Results—The model accurately fit development of
injuries in the sample population but overestimated
development of injuries in the southern California
racehorse population. Development of and recovery
from PSAI were correlated with distance run at high
speeds. Reducing by 20% the number of sprints run
at distances > 6 furlongs significantly reduced modeled
annual CDY and SSAI incidence by 9%.
Conclusions and Clinical Relevance—Reducing the
number of sprints at distances > 6 furlongs, particularly
among horses with PSAI, reduces risk of CDY
and SSAI. (Am J Vet Res 2003;64:328–337)
Objective—To create a stochastic model to quantify
the risk that shipments of cattle from regions within
the United States would contain animals seropositive
for bluetongue virus and to determine shipment-level
accuracy of serologic testing by use of a competitive
Sample Population—19,216 shipments containing
528,918 cattle and calves.
Procedure—Data were obtained on number of animals
and state of origin of cattle in export shipments
originating within the United States between January
1994 and March 2002. Probability distributions for
size of export shipments were determined for all
states within the United States, and distributions for
agar gel immunodiffusion and c-ELISA accuracy (sensitivity
and specificity) were determined from expert
opinion and review of the literature. The model simulated
selection of a shipment and then determined
the probability that a threshold number or percentage
of cattle within that shipment would have a positive
c-ELISA result. Shipment-level sensitivity, specificity,
positive-predictive value, and negative-predictive
value were calculated.
Results—Substantial differences were evident in the
regional probability of a shipment being declared positive,
with shipments from northeastern states having
the lowest probability and shipments from southwestern
states having the highest probability. The c-
ELISA had variable predictive values at the shipment
level, depending on the threshold used and the prevalence
of antibody-positive cattle within the region.
Conclusions and Clinical Relevance—Results from
this study will aid importers in making scientifically
based decisions regarding risk of importing antibodypositive
cattle. ( Am J Vet Res 2003;64:520–529)
Objective—To investigate herd characteristics and management practices associated with a high seroprevalence of Mycobacterium avium subsp paratuberculosis (MAP) in dairy herds in central California.
Sample Population—60 randomly selected cows from each of 21 dairy herds.
Procedures—Sera of selected cows were tested for antibodies against MAP by use of an ELISA test kit. Cows with a test sample-to-positive control sample (S:P) ratio of ≥ 0.25 were considered seropositive, and herds with ≥ 4% seropositive cows were considered high-seroprevalence herds. Data on herd characteristics and management practices were collected via interviews with owners. Bayesian logistic regression was used to model the predictive probability of a herd having a high seroprevalence on the basis of various herd characteristics and management practices.
Results—9 of 21 (43%) herds were classified as high-seroprevalence herds. Five variables (history of previous signs of paratuberculosis in the herd, herd size, exposing cattle to water from manure storage lagoons, feeding unsalable milk to calves, and exposing heifers ≤ 6 months old to manure of adult cows) were included in the predictive model on the basis of statistical and biological considerations. In large herds, the predictive probability of a high seroprevalence of MAP infection decreased from 0.74 to 0.39 when management changed from poor to good practices. In small herds, a similar decrease from 0.64 to 0.29 was predicted.
Conclusions and Clinical Relevance—The seroprevalence of MAP infection in California dairies may be reduced by improvements in herd management practices.
Objective—To estimate cat population size, management, and outside fecal deposition and evaluate attitudes of cat owners and nonowners to stray animal control, water pollution, and wildlife protection.
Sample Population—294 adult residents of Cayucos, Los Osos, and Morro Bay, Calif.
Results—The region's cat population was estimated at 7,284 owned and 2,046 feral cats, and 38% of surveyed households owned a mean of 1.9 cats/household. Forty-four percent of cats defecated outside >75% of the time. Annual fecal deposition (wet weight) by owned cats in the 3 communities was estimated to be 77.6 tonnes (76.4 tons). Cat owners were more likely to oppose cat licensing and impounding stray cats and support trap-neuter-return for stray cats and less likely to be concerned about water pollution, than were noncat owners.
Conclusions and Clinical Relevance—Feral cats represented a sizeable proportion (22%) of the free roaming cats in this area and could be contributing 30.0 tonnes (29.5 tons) of feces to the environment per year. However, feral cats are not the principal source of fecal loading because owned cats defecating outdoors contribute an estimated 77.6 tonnes (76.4 tons) or 72% of the annual outdoor fecal deposition.
Objective—To compare macrostructural and microstructural features of proximal sesamoid bones (PSBs) from horses with and without PSB midbody fracture to gain insight into the pathogenesis of PSB fracture.
Sample Population—PSBs from 16 Thoroughbred racehorses (8 with and 8 without a PSB midbody fracture).
Procedures—Parasagittal sections of fractured and contralateral intact PSBs from horses with a PSB fracture and an intact PSB from age- and sex-matched control horses without a PSB fracture were evaluated for visual, radiographic, microradiographic, histologic, and his-tomorphometric differences in bone porosity, vascular channels, heme pigment, trabecular anisotropy, and pathological findings.
Results—Fractured PSBs and their contralateral intact PSBs had more compacted trabecular bone than did control PSBs. Focal repair or remodeling was evident in the palmar aspect of many fractured and contralateral intact PSBs. Fracture coincided with microstructural features and propagated from the flexor to the articular surface.
Conclusions and Clinical Relevance—Fractured PSBs had adapted to high loading but had focal evidence of excessive remodeling and porosity that likely predisposed the horses to complete fracture and catastrophic injury. Detection of focal injury before complete fracture provides an opportunity for prevention of catastrophic injury. Development of diagnostic imaging methods to assess porosity of PSBs may help to identify at-risk horses and allow for modifications of training and racing schedules to reduce the incidence of PSB fracture in Thoroughbred racehorses.
Objective—To validate a luciferase bioassay, which is
based on a recombinant mouse hepatoma cell line, for
the detection of exposure to petroleum in mustelid
Animals—122 American mink (Mustela vison) and 15
sea otters (Enhydra lutris).
Procedures—Mink were exposed to Bunker C fuel oil or
Alaska North Slope crude oil externally as a single exposure
or internally via low dose concentrations in their
ration for 6 months. Serum samples were analyzed for
cytochrome P450 1A1 induction by quantification of
luciferase activity in the bioassay. Mink liver specimens
were also evaluated for cytochrome P450 1A1 induction
by quantification of ethoxyresorufin-o-deethylase activity.
Serum collected from exposed and unexposed sea
otters was also analyzed using the luciferase bioassay.
Results—Serum samples from mink externally
exposed to petroleum had significantly increased
luciferase activities at 1 week after exposure. Serum
samples taken at later time points or from mink
exposed to either product in the ration did not cause
significant luciferase induction. Samples from otters
exposed to petroleum had significantly higher
luciferase induction as compared with samples from
otters not exposed to petroleum at 2 and 8 years after
the spill. Cytochrome P450 1A1 activity in liver specimens
collected from mink that were internally
exposed through diet was significantly increased at
the conclusion of our study.
Conclusion and Clinical Relevance—The luciferase
bioassay is a sensitive and specific method for determining
recent exposure to petroleum in mink. The
lack of luciferase activity in serum samples collected
from mink greater than 1 week after experimental
exposure was likely attributable to lower overall petroleum
exposure in our trial, compared with natural
exposures. (Am J Vet Res 2002;63:963–968)