OBJECTIVE To evaluate the effect of lipopolysaccharide (LPS) on apoptosis of equine neutrophils in vitro.
SAMPLE Venous blood samples from 40 adult horses.
PROCEDURES Neutrophils were isolated from blood samples and cultured with or without LPS from Escherichia coli O55:B5 for 12 or 24 hours. Neutrophil apoptosis was assessed by use of cytologic examination, annexin V and propidium iodide staining quantified with flow cytometry, coincubation with inducers of intrinsic and extrinsic apoptosis or a toll-like receptor (TLR) 4 inhibitor, and measurement of caspase-3, -8, and -9 activities.
RESULTS Treatment with LPS resulted in a significant delay in apoptosis after incubation for 12 and 24 hours (neutrophils from blood samples of 40 horses). There was a significant correlation between increases in LPS dose and decreases in apoptosis after incubation for 24 hours (3 experiments, each of which involved neutrophils obtained from the same 3 horses at 3 separate times). Caspase-9 activity, but not caspase-3 or -8 activity, was significantly reduced in LPS-treated neutrophils after incubation for 12 hours (neutrophils from blood samples of 17 horses). Treatment with a TLR4 inhibitor or intrinsic and extrinsic inducers of apoptosis prevented LPS-delayed apoptosis.
CONCLUSIONS AND CLINICAL RELEVANCE LPS treatment delayed apoptosis of equine neutrophils in vitro for up to 24 hours in a dose-dependent manner by alteration of the intrinsic pathway of apoptosis and was dependent on TLR4 signaling. Increased neutrophil life span may contribute to the development of a systemic inflammatory response syndrome in endotoxemic horses.
Objective—To evaluate the effect of dental floating
on the position of the mandible relative to the maxilla
(a measure of rostrocaudal mobility [RCM] of the
mandible) during extension and flexion of the head of
Design—Randomized controlled blinded trial.
Animals—59 horses housed in 1 barn.
Procedure—Horses were formally randomized into a
treatment (n = 33) or control (26) group. All horses
were sedated, and the distance between rostral portions
of the upper and lower incisor arcades were
determined with the head fully extended and flexed at
the poll (the difference in measurements represented
the RCM of the mandible). The oral cavity was examined.
For the treatment group, dental floating was
performed, and the incisor arcade measurements
Results—Dental correction resulted in a significant
increase in RCM of the mandible in 31 of 33 horses.
The mobility was greater in heavy horses than that
detected in other breed classifications. Age and number
of dental lesions did not significantly affect mobility
before or after dental floating.
Conclusions and Clinical Relevance—Dental floating
increased RCM of the mandible, but measurement
of this variable was not an indicator of the number
or extent of dental lesions, and no specific dental
abnormality appeared to significantly affect RCM of
the mandible in horses. In horses, measurement of
RCM of the mandible can be used as a guide to determine
whether dental correction is necessary; after
dental floating, it can be used to ensure that irregularities
of the occlusal surface have been corrected. (J
Am Vet Med Assoc 2003;223:666–669)
Objective—To describe clinical signs and clinicopathologic
findings in donkeys with hypothermia.
Animals—10 hypothermic donkeys.
Procedure—Information on signalment, history,
physical examination findings, results of diagnostic
tests, treatments, and necropsy findings was extracted
from medical records of all donkeys with hypothermia
between 1988 and 1998 and compared with information
from medical records of all normothermic donkeys
and hypothermic horses admitted to the hospital
during the same period.
Results—Donkeys were more likely to be hypothermic
than horses. The mean age of hypothermic donkeys
was 6 years (range, 7 months to 11 years), compared
with 4.2 years (range, < 1 month to 15 years)
for normothermic donkeys; this difference was not
significant. Ten of 12 horses with hypothermia were
neonates; there were no hypothermic neonatal donkeys.
At admission, 7 of 8 hypothermic donkeys were
in good body condition and all hypothermic donkeys
were weak. Six hypothermic donkeys were able to
maintain sternal recumbency, 1 remained in lateral
recumbency, and 3 were able to stand. Of the 10
hypothermic donkeys, 2 survived, 1 died, and 7 were
euthanatized. Histologically, the thyroid glands from 4
of 5 hypothermic donkeys appeared abnormal and
were similar to those of foals with hypothyroidism.
During the months that hypothermic donkeys were
admitted, there was not a significant difference in
environmental temperatures on days of admission
between hypothermic and normothermic donkeys.
Conclusions and Clinical Relevance—Hypothermia
is a problem in donkeys during cold winter months,
and may not be secondary to other diseases or related
to diet or management. (J Am Vet Med Assoc
Objective—To determine whether occlusal angle of
the premolar and molar teeth (ie, molar occlusal
angle) was associated with feed digestibility, water
balance, or fecal particle size in adult horses.
Animals—40 pregnant mares ranging from 3 to 19
Procedure—The horses were randomly allocated to 1
of 5 feeding groups with 8 horses/group. Horses
were sedated, and molar occlusal angle was measured
with 2 methods. An oral examination was performed,
and total number of dental abnormalities was
recorded. Feed digestibility, water balance, and fecal
particle size were measured 7 and 16 weeks later.
Results—Molar occlusal angle ranged from 6.3° to
19.3° and was not significantly associated with feed
digestibility, water balance, or fecal particle size. The
number of dental abnormalities was not associated
with feed digestibility. Molar occlusal angle did not
vary significantly with horse age.
Conclusions and Clinical Relevance—Results indicate
that molar occlusal angles between 6° and 19° do
not adversely affect feed digestibility, water balance,
or fecal particle size in adult horses. Additionally, there
was no association between age and molar occlusal
angle. (J Am Vet Med Assoc 2005;227:110–113)
Objective—To investigate the effect of routine dental
floating on weight gain, body condition score, feed
digestibility, and fecal particle size in pregnant mares
fed various diets.
Design—Randomized controlled clinical trial.
Animals—56 pregnant mares.
Procedure—Mares were randomly allocated to 1 of 4
feed groups (n = 14 mares/group). All horses were
sedated and an oral examination was performed, after
which dental floating was performed on 7 horses in
each group. Body weight was measured, and a body
condition score was assigned before and at various
times for 24 weeks after dental floating. Feed
digestibility and fecal particle size were analyzed 7
and 19 weeks after dental floating.
Results—Weight gain, change in body condition
score, feed digestibility, and fecal particle size were
not significantly different between horses that underwent
dental floating and untreated control horses. In
contrast, weight gain was significantly associated
with feed group. In the control horses, neither the
number of dental lesions nor the presence of any particular
type of lesion at the time of the initial oral
examination was significantly associated with subsequent
Conclusions and Clinical Relevance—Results suggest
that dental floating does not result in significant
short-term changes in body weight, body condition
score, feed digestibility, or fecal particle size in healthy
pregnant mares. Further studies are necessary to
determine the clinical utility of regular dental floating
in apparently healthy horses. (J Am Vet Med Assoc
Objective—To describe 3 epidemics of respiratory
tract disease caused by influenza virus infections in a
large population of horses.
Design—Cross-sectional and prospective longitudinal
Animals—All horses stabled at a Thoroughbred racetrack.
Procedure—During a 3-year period, descriptive
information was collected as horses arrived at the
racetrack and throughout race meetings. Routine
observations and physical examinations were used to
classify horses' disease status. Cause of epidemics
was established by use of serologic testing and identification
of influenza virus in nasal secretions.
Results—An epidemic of respiratory tract disease
caused by influenza virus infections was identified during
each year of the study. Attack rates of infectious
upper respiratory tract disease (IURD) ranged from 16
to 28%. Incidence of disease caused by influenza virus
infections during racing seasons in the second and
third years was 27 and 37 cases/1,000 horses/mo,
respectively. Physical distributions of stall locations
revealed that affected horses were stabled throughout
the population; horses affected later in epidemics
were often clustered around horses affected earlier.
Mucopurulent nasal discharge and coughing were
observed in 83 and 62% of horses with IURD, respectively.
Median duration of clinical disease was 11 days.
Serologic testing was the most sensitive method used
to detect influenza virus infections; 76% of affected
horses seroconverted to influenza virus.
Conclusion and Clinical Relevance—Epidemics of
IURD were observed annually in association with
influenza virus infections. Few precautions were
taken to limit spread of infection. Preventing or
decreasing the likelihood of exposure and improving
immunity in the population could substantially
decrease risk of disease in similar populations. (J Am
Vet Med Assoc 2000;216:535–544)
Objective—To identify risk factors associated with
respiratory tract disease in horses during 3 epidemics
caused by influenza virus infections.
Design—Cross-sectional and prospective longitudinal
Animals—1,163 horses stabled at a Thoroughbred
Procedure—Investigations were conducted during a
3-year period. An epidemic of respiratory tract disease
caused by influenza virus infections was identified
in each year. Routine observations and physical
examinations were used to classify horses' disease
status. Data were analyzed to identify factors associated
with development of disease.
Results—Results were quite similar among the epidemics.
Concentrations of serum antibodies against
influenza virus and age were strongly associated with
risk of disease; young horses and those with low antibody
concentrations had the highest risk of disease.
Calculation of population attributable fractions suggested
that respiratory tract disease would have been prevented
in 25% of affected horses if all horses had high
serum antibody concentrations prior to exposure.
However, recent history of vaccination was not associated
with reduction in disease risk. Exercise ponies had
greater risk of disease than racehorses, which was likely
attributable to frequent horse-to-horse contact.
Conclusion and Clinical Relevance—Particular
attention should be paid to young horses, those with
low serum antibody concentrations, and horses that
have frequent contact with other horses when
designing and implementing control programs for respiratory
tract disease caused by influenza virus infections.
It appears that control programs should not rely
on the efficacy of commercial vaccines to substantially
reduce the risk of disease caused by influenza virus
infections. (J Am Vet Med Assoc 2000;216:545–550)
Objective—To evaluate the effect of hemi-circumferential
periosteal transection and elevation (HCPTE) in
foals with experimentally induced angular limb deformities.
Animals—10 healthy foals.
Procedure—When foals were 30 days old, transphyseal
bridge implants were placed on the lateral
aspects of both distal radial physes. At 90 days of age
(or when 15 degrees of angulation had developed),
implants were removed, and HCPTE was performed
on 1 limb. Foals were confined in small pens after
surgery; the front feet of the foals were rasped weekly
to maintain medial-to-lateral hoof wall balance.
Dorsopalmar radiographic projections of the carpi
were obtained before HCPTE and 2, 4, 6, 8, and 48
Results—At the time of transphyseal bridge removal
and HCPTE, both treated and control limbs were
observed to have a significantly greater carpal valgus,
compared with the initial degree of angulation at 30
days of age. Following HCPTE or sham surgery, all
limbs straightened over the subsequent 2 months of
the study. Median angulation was not significantly different
between treated and control limbs at any time
during the study.
Conclusions and Clinical Relevance—Results suggest
that in foals with experimentally induced limb deformities,
HCPTE was no more effective than stall confinement
and hoof trimming alone for correction of the
deformity. (J Am Vet Med Assoc 2002;221:536–540)
Objective—To determine whether maternally derived antibodies interfere with the mucosal immune response following intranasal (IN) vaccination of newborn calves with a multivalent modified-live virus vaccine.
Design—Randomized controlled clinical trial.
Animals—23 newborn Holstein bull calves.
Procedures—Calves received colostrum and were assigned to group A (unvaccinated control calves), group B (IN vaccination on day 0), or group C (IN vaccination on days 0 and 35). Serum and nasal secretion sample (NSS) titers of antibodies specific for bovine herpesvirus 1, bovine viral diarrhea virus 1, and bovine viral diarrhea virus 2; WBC counts; and NSS interferon concentrations were determined up to day 77.
Results—Calves had high serum titers of maternally derived antibodies specific for vaccine virus antigens on day 0. High IgA and low IgG titers were detected in NSSs on day 0; NSS titers of IgA decreased by day 5. Group B and C NSS IgA titers were significantly higher than those of group A on days 10 through 35; group C IgA titers increased after the second vaccination. Serum antibody titers decreased at a similar rate among groups of calves. Interferons were not detected in NSSs, and calves did not develop leukopenia.
Conclusions and Clinical Relevance—IN vaccination of newborn calves with high concentrations of virus-neutralizing antibodies increased NSS IgA titers but did not change serum antibody titers. Revaccination of group C calves on day 35 induced IgA production. Intranasal vaccination with a modified-live virus vaccine was effective in calves that had maternally derived antibodies.
Objective—To determine comparative efficacy of
vaccines administered IM and intranasally, used alone
or sequentially, to protect puppies from infection with
Bordetella bronchiseptica and determine whether
systemic or mucosal antibody response correlated
Design—Randomized controlled trial.
Animals—50 specific-pathogen-free Beagle puppies.
Procedure—In 2 replicates of 25 dogs each, 14-weekold
puppies that were vaccinated against canine distemper
virus and parvovirus were vaccinated against B bronchiseptica via intranasal, IM, intranasal-IM, or IMintranasal
administration or were unvaccinated controls.
Puppies were challenge exposed via aerosol administration
of B bronchiseptica 2 weeks after final vaccination.
Clinical variables and systemic and mucosal antibody
responses were monitored for 10 days after challenge
exposure. Puppies in replicate 1 were necropsied
for histologic and immunohistochemical studies.
Results—Control puppies that were seronegative
before challenge exposure developed paroxysmal
coughing, signs of depression, anorexia, and fever.
Vaccinated puppies (either vaccine) that were seronegative
before challenge exposure had fewer clinical signs.
Puppies that received both vaccines had the least
severe clinical signs and fewest lesions in the respiratory
tract. Vaccinated dogs had significantly higher concentrations
of B bronchiseptica-reactive antibodies in
serum saliva before and after challenge. Antibody concentrations
were negatively correlated with bacterial
growth in nasal cavity and pharyngeal samples after
Conclusions and Clinical Relevance—Parenterally
and intranasally administered vaccines containing B
bronchiseptica may provide substantial protection
from clinical signs of respiratory tract disease associated
with infection by this bacterium. Administration
of both types of vaccines in sequence afforded the
greatest degree of protection against disease. (J Am
Vet Med Assoc 2001;218:367–375)