Objective—To evaluate the use of sucrose permeability
testing to detect ulcers in the gastric squamous
mucosa of horses.
Animals—13 adult horses ranging from 5 to 19 years
Procedure—Following induction of gastric ulcers by
intermittent feed deprivation, horses underwent
sucrose permeability testing (administration of
sucrose by nasogastric intubation followed by collection
of urine at 2 and 4 hours after intubation) and gastric
endoscopy. Squamous ulcers were assigned a
severity score (range, 0 to 3) by use of an established
scoring system. Horses were subsequently administered
omeprazole for 21 days, and sucrose testing
and endoscopy were repeated. Pair-wise comparisons
of urine sucrose concentration were made
between horses with induced ulcers before and after
omeprazole treatment. Urine sucrose concentrations
also were compared on the basis of ulcer severity
Results—Urine sucrose concentrations and ulcer
severity scores were significantly higher in horses
with induced ulcers before omeprazole treatment
than after treatment. Urine sucrose concentrations
were significantly higher for horses with ulcer severity
scores > 1. Use of a cut-point value of 0.7 mg/mL
revealed that the apparent sensitivity and specificity
of sucrose permeability testing to detect ulcers with
severity scores > 1 was 83% and 90%, respectively.
Results were similar after adjusting sucrose concentrations
for urine osmolality.
Conclusions and Clinical Relevance—Urine sucrose
concentration appears to be a reliable but imperfect
indicator of gastric squamous ulcers in horses.
Sucrose permeability testing may provide a simple,
noninvasive test to detect and monitor gastric ulcers
in horses. ( Am J Vet Res 2004;65:31–39)
Objective—To determine whether mares are a clinically important source of Rhodococcus equi for their foals.
Sample Population—171 mares and 171 foals from a farm in Kentucky (evaluated during 2004 and 2005).
Procedures—At 4 time points (2 before and 2 after parturition), the total concentration of R equi and concentration of virulent R equi were determined in fecal specimens from mares by use of quantitative bacteriologic culture and a colony immunoblot technique, respectively. These concentrations for mares of foals that developed R equi–associated pneumonia and for mares with unaffected foals were compared. Data for each year were analyzed separately.
Results—R equi–associated pneumonia developed in 53 of 171 (31%) foals. Fecal shedding of virulent R equi was detected in at least 1 time point for every mare; bacteriologic culture results were positive for 62 of 171 (36%) mares at all time points. However, compared with dams of unaffected foals, fecal concentrations of total or virulent R equi in dams of foals with R equi–associated pneumonia were not significantly different.
Conclusions and Clinical Relevance—Results indicate that dams of foals with R equi–associated pneumonia did not shed more R equi in feces than dams of unaffected foals; therefore, R equi infection in foals was not associated with comparatively greater fecal shedding by their dams. However, detection of virulent R equi in the feces of all mares during at least 1 time point suggests that mares can be an important source of R equi for the surrounding environment.
Objective—To identify factors significantly associated
with an epidemic of fibrinous pericarditis during
spring 2001 among horses in central Kentucky.
Animals—38 horses with fibrinous pericarditis and
30 control horses examined for other reasons.
Procedure—A questionnaire was developed to solicit
information regarding a wide range of management
practices and environmental exposures from farm
owners or managers.
Results—The following factors were found in bivariate
analyses to be significantly associated with an
increased risk of pericarditis: being from a farm with
mares and foals affected by mare reproductive loss
syndrome, exposure to Eastern tent caterpillars in or
around horse pastures, younger age, shorter duration
of residence in Kentucky and at the farm of current
residence, being fed hay grown outside Kentucky, a
lack of access to pond water, access to orchard grass
for grazing, and a lack of direct contact with cattle. In
multivariate logistic regression analyses, only variables
related to caterpillar exposure and age were significantly
associated with fibrinous pericarditis.
Conclusions and Clinical Relevance—Results suggest
that fibrinous pericarditis in horses may be associated
with mare reproductive loss syndrome. Exposure
to Eastern tent caterpillars was the greatest risk factor
for development of fibrinous pericarditis. The distribution
of times of diagnosis of fibrinous pericarditis was
consistent with a point-source epidemic. (J Am Vet Med
Objective—To determine whether isolation and virulence
of Rhodococcus equi from soil and infected
foals are associated with clinical disease.
Design—Cross-sectional and case-control study.
Sample Population—R equi isolates from 50 foals
with pneumonia and soil samples from 33 farms with
and 33 farms without a history of R equi infection
(affected and control, respectively).
Procedure—R equi was selectively isolated from soil
samples. Soil and clinical isolates were evaluated for
virulence-associated protein antigen plasmids (VapAP)
and resistance to the β-lactam antibiotics penicillin
G and cephalothin. Microbiologic cultures and VapA-P
assays were performed at 2 independent laboratories.
Results—VapA-P was detected in 49 of 50 (98%) clinical
isolates; there was complete agreement between
laboratories. Rhodococcus equi was isolated from soil
on 28 of 33 (84.8%) affected farms and 24 of 33
(72.7%) control farms, but there was poor agreement
between laboratories. Virulence-associated protein
antigen plasmids were detected on 14 of 66 (21.2%)
farms by either laboratory, but results agreed for only
1 of the 14 VapA-P-positive farms. We did not detect
significant associations between disease status and
isolation of R equi from soil, detection of VapA-P in soil
isolates, or resistance of soil isolates to β-lactam
antibiotics. No association between β-lactam antibiotic
resistance and presence of VapA-P was detected.
Conclusions and Clinical Relevance—On the basis of
soil microbiologic culture and VapA-P assay results, it is
not possible to determine whether foals on a given farm
are at increased risk of developing disease caused by R
equi. (J Am Vet Med Assoc 2000;217:220–225)
Objective—To identify factors associated with abortions
of mares during late gestation attributed to mare
reproductive loss syndrome (MRLS).
Animals—282 broodmares from 62 farms in central
Kentucky, including 137 mares that had late-term
abortions (LTAs) associated with MRLS, 98
mares from the same farms that did not abort, and
48 mares that aborted from causes other than
Procedure—Farm managers were interviewed to
obtain data on a wide range of management practices
and environmental exposures for the mares. Data for
case and control horses were compared to identify
risk factors for a mare having a MRLS-associated LTA
Results—Several factors increased the risk of mares
having MRLS-LTAs, including increased amount of
time at pasture, less time in a stall, feeding concentrate
on the ground, higher proportion of diet derived
from grazing pasture, being fed in pasture exclusively
during the 4-week period prior to abortion, access to
pasture after midnight during the 4-week period prior
to abortion, and drinking from a water trough or not
having access to water buckets or automatic waterers.
Conclusions and Clinical Relevance—Analysis indicates
that exposure to pasture predisposed mares to
having MRLS-LTAs and stillborn foals. Methods for
limiting exposure to pasture (keeping mares in stalls
longer) during environmental conditions similar to
those seen in 2001 should reduce the risk of mares
having MRLS-LTAs. (J Am Vet Med Assoc 2003;222:199–209)
Objective—To determine the sensitivity and specificity
of 5 serologic assays used to diagnose Rhodococcus
equi pneumonia in foals and to determine whether any
of the assays could be used to identify affected foals
prior to the onset of clinical signs or to differentiate
between affected and unaffected foals when clinical
signs first become apparent.
Design—Nested case-control study.
Procedure—Serum samples were obtained from all
foals at 2, 4, and 6 or 7 weeks of age. Additional samples
were obtained from affected foals at the time of
diagnosis of R equi pneumonia and from agematched
unaffected foals. Samples were tested with
3 ELISA, an agar gel immunodiffusion assay, and a
synergistic hemolysis inhibition assay.
Results—Sensitivity and specificity data indicated that
none of the assays could be used to reliably differentiate
affected from unaffected foals at any testing period.
Proportions of foals that had an increase in test values
between paired samples collected at 4 and 6 or 7
weeks of age were not significantly different between
affected and unaffected foals. For all assays, result
values increased significantly over time; however, the
rate of increase was not significantly different
between affected and unaffected foals.
Conclusions and Clinical Relevance—Results suggest
that serologic assays, whether performed on single
or paired samples, cannot be used to reliably establish,
confirm, or exclude a diagnosis of R equi pneumonia
in foals. (J Am Vet Med Assoc 2002;221:825–833)
Objective—To compare isolates of Rhodococcus
equi on the basis of geographic source and virulence
status by use of pulsed-field gel electrophoresis
Sample Population—290 isolates of R equi(218 virulent
isolates from foals and 72 avirulent isolates from
feces, soil, and respiratory tract samples) obtained
between 1985 and 2000 from horses and horse farms
from 4 countries.
Procedure—DNA from isolates was digested with
the restriction enzyme AseI and tested by use of
PFGE. Products were analyzed for similarities in banding
patterns by use of dendrograms. A similarity
matrix was constructed for isolates, and the matrix
was tested for nonrandom distributions of similarity
values with respect to groupings of interest.
Results—There was little grouping of isolates on the
basis of country, virulence status, or region within
Texas. Isolates of R equi were generally < 80% similar,
as determined by use of PFGE. Isolates from the
same farm generally were rarely of the same strain.
Conclusions and Clinical Relevance—Considerable
chromosomal variability exists among isolates of R
equi obtained from the same farm, sites within Texas,
or among countries from various continents. Only
rarely will it be possible to link infections to a given
site or region on the basis of analysis of isolates by
use of PFGE of chromosomal DNA. (Am J Vet Res 2003;64:153–161)
Objective—To determine whether the concentration of airborne virulent Rhodococcus equi varied by location (stall vs paddock) and month on horse farms.
Sample—Air samples from stalls and paddocks used to house mares and foals on 30 horse breeding farms in central Kentucky.
Procedures—Air samples from 1 stall and 1 paddock were obtained monthly from each farm from January through June 2009. Concentrations of airborne virulent R equi were determined via a modified colony immunoblot assay. Random-effects logistic regression was used to determine the association of the presence of airborne virulent R equi with location from which air samples were obtained and month during which samples were collected.
Results—Of 180 air samples, virulent R equi was identified in 49 (27%) and 13 (7%) obtained from stalls and paddocks, respectively. The OR of detecting virulent R equi in air samples from stalls versus paddocks was 5.2 (95% confidence interval, 2.1 to 13.1). Of 60 air samples, virulent R equi was identified in 25 (42%), 18 (30%), and 6 (10%) obtained from stalls during January and February, March and April, and May and June, respectively. The OR of detecting virulent R equi from stall air samples collected during May and June versus January and February was 0.22 (95% confidence interval, 0.08 to 0.63).
Conclusions and Clinical Relevance—Foals were more likely to be exposed to airborne virulent R equi when housed in stalls versus paddocks and earlier (January and February) versus later (May and June) during the foaling season.
Objective—To determine whether airborne concentrations of virulent Rhodococcus equi at 2 horse breeding farms varied on the basis of location, time of day, and month.
Sample Population—2 farms in central Kentucky with recurrent R equi-induced pneumonia in foals.
Procedures—From February through July 2008, air samples were collected hourly for a 24-hour period each month from stalls and paddocks used to house mares and their foals. Concentrations of airborne virulent R equi were determined via a modified colony immunoblot technique. Differences were compared by use of zero-inflated negative binomial methods to determine effects of location, time, and month.
Results—Whether mares and foals were housed predominantly in stalls or paddocks significantly affected results for location of sample collection (stall vs paddock) by increasing airborne concentrations of virulent R equi at the site where horses were predominantly housed. Airborne concentrations of virulent R equi were significantly higher from 6:00 pm through 11:59 pm than for the period from midnight through 5:59 am. Airborne concentrations of virulent R equi did not differ significantly between farms or among months.
Conclusions and Clinical Relevance—Airborne concentrations of virulent R equi were significantly increased when horses were predominantly housed at the site for collection of air samples (ie, higher in stalls when horses were predominantly housed in stalls and higher in paddocks when horses were predominantly housed in paddocks). Concentrations of virulent R equi among air samples collected between the hours of 6:00 am and midnight appeared similar.
Objective—To determine whether soil concentrations of total or virulent Rhodococcus equi differed among breeding farms with and without foals with pneumonia caused by R equi.
Sample Population—37 farms in central Kentucky.
Procedures—During January, March, and July 2006, the total concentration of R equi and concentration of virulent R equi were determined by use of quantitative bacteriologic culture and a colony immunoblot technique, respectively, in soil specimens obtained from farms. Differences in concentrations and proportion of virulent isolates within and among time points were compared among farms.
Results—Soil concentrations of total or virulent R equi did not vary among farms at any time point. Virulent R equi were identified in soil samples from all farms. Greater density of mares and foals was significantly associated with farms having foals with pneumonia attributable to R equi. Among farms with affected foals, there was a significant association of increased incidence of pneumonia attributable to R equi with an increase in the proportion of virulent bacteria between samples collected in March and July.
Conclusions and Clinical Relevance—Results indicated that virulent R equi were commonly recovered from soil of horse breeding farms in central Kentucky, regardless of the status of foals with pneumonia attributable to R equi on each farm. The incidence of foals with pneumonia attributable to R equi can be expected to be higher at farms with a greater density of mares and foals.