Objective—To determine whether the concentrations of airborne virulent Rhodococcus equi in stalls housing foals during the first 2 weeks after birth are associated with subsequent development of R equi pneumonia in those foals.
Sample—Air samples collected from foaling stalls and holding pens in which foals were housed during the first 2 weeks after birth.
Procedures—At a breeding farm in Texas, air samples (500 L each) were collected (January through May 2011) from stalls and pens in which 121 foals were housed on day 1 and on days 4, 7, and 14 after birth. For each sample, the concentration of airborne virulent R equi was determined with an immunoblot technique. The association between development of pneumonia and airborne R equi concentration was evaluated via random-effects Poisson regression analysis.
Results—Some air samples were not available for analysis. Of the 471 air samples collected from stalls that housed 121 foals, 90 (19%) contained virulent R equi. Twenty-four of 121 (20%) foals developed R equi pneumonia. Concentrations of virulent R equi in air samples from stalls housing foals that developed R equi pneumonia were significantly higher than those in samples from stalls housing foals that did not develop pneumonia. Accounting for disease effects, air sample concentrations of virulent R equi did not differ significantly by day after birth or by month of birth.
Conclusions and Clinical Relevance—Exposure of foals to airborne virulent R equi during the first 2 weeks after birth was significantly (and likely causally) associated with development of R equi pneumonia.
OBJECTIVE To determine the effects of oral omeprazole administration on the fecal and gastric microbiota of healthy adult horses.
ANIMALS 12 healthy adult research horses.
PROCEDURES Horses were randomly assigned to receive omeprazole paste (4 mg/kg, PO, q 24 h) or a sham (control) treatment (tap water [20 mL, PO, q 24 h]) for 28 days. Fecal and gastric fluid samples were collected prior to the first treatment (day 0), and on days 7, 28, 35, and 56. Sample DNA was extracted, and bacterial 16S rRNA gene sequences were amplified and sequenced to characterize α and β diversity and differential expression of the fecal and gastric microbiota. Data were analyzed by visual examination and by statistical methods.
RESULTS Composition and diversity of the fecal microbiota did not differ significantly between treatment groups or over time. Substantial variation in gastric fluid results within groups and over time precluded meaningful interpretation of the microbiota in those samples.
CONCLUSIONS AND CLINICAL RELEVANCE Results supported that omeprazole administration had no effect on fecal microbiota composition and diversity in this group of healthy adult horses. Small sample size limited power to detect a difference if one existed; however, qualitative graphic examination supported that any difference would likely have been small and of limited clinical importance. Adequate data to evaluate potential effects on the gastric microbiota were not obtained. Investigations are needed to determine the effects of omeprazole in horses with systemic disease or horses receiving other medical treatments.
OBJECTIVE To compare bony changes of the third metacarpal bone (MC3) of Thoroughbred racehorse cadavers with (cases) or without (controls) catastrophic condylar fracture by use of standing MRI.
SAMPLE 140 forelimbs from 26 case horses (both forelimbs) and 88 control horses (single forelimb).
PROCEDURES Bone marrow lesions (BMLs), identified as a decrease in T1-weighted (T1W) signal and increases in T2*-weighted (T2*W) and short tau inversion recovery (STIR) signals, and dense bone volume percentage (DBVP), identified as decreases in T1W, T2*W, and STIR signals, in the distopalmar aspect of MC3 were recorded. Logistic regression was used to compare fractured and nonfractured limbs of cases and fractured limbs of cases with randomly selected limbs of controls.
RESULTS Among cases, fractured limbs were significantly more likely to have BMLs (26/26 [100%]) than were nonfractured limbs (7/26 [27%]). Fractured limbs of cases were significantly more likely to have BMLs (26/26 [100%]) than were limbs of controls (6/88 [7%]). Among cases, there was no significant difference in DBVP between fractured and nonfractured limbs in lateral (26% vs 21%, respectively) or medial (25% vs 20%, respectively) condyles. However, DBVP was significantly greater in fractured limbs of cases than in limbs of controls for lateral (26% vs 16%, respectively) and medial (25% vs 18%, respectively) condyles.
CONCLUSIONS AND CLINICAL RELEVANCE Standing MRI revealed a significantly greater degree of bone change in racehorses with condylar fracture when comparing fractured and nonfractured limbs of case horses and fractured limbs of case horses with randomly selected limbs of control horses.
Objective—To determine the effects of treatment with platelet- and leukocyte-rich plasma (PRP) on future 2-, 3-, and 4-year-old racing performance of yearling Thoroughbreds with proximal sesamoid bone inflammation and associated suspensory ligament branch (SLB) desmitis.
Design—Randomized clinical trial.
Animals—39 yearling Thoroughbreds.
Procedures—Yearling Thoroughbreds with radiographic evidence of performance-limiting proximal sesamoid bone inflammation and ultrasonographic evidence of associated SLB desmitis were identified and randomly assigned to undergo PRP (treatment group) or saline (0.9% NaCl) solution (control group) injection at the affected SLB-proximal sesamoid bone junction. Race records of horses for the 2-, 3-, and 4-year-old racing years were obtained. Data regarding amount of money earned and number of races started were used as outcome measures, and results for groups were compared.
Results—Horses treated with PRP were significantly more likely to start at least 1 race during the 2-year-old racing year than were horses treated with saline solution; no significant differences were detected between groups regarding that variable for the 3- and 4-year-old racing years. No significant differences between groups were detected regarding earnings for any racing year.
Conclusions and Clinical Relevance—Although PRP-treated horses were more likely to start a race during the 2-year-old racing year versus control group horses, results for horses in each group were not significantly different for the 3- and 4-year-old racing years. Therefore, the PRP treatment protocol evaluated in this study did not seem to improve future racing performance of yearling Thoroughbreds with proximal sesamoid bone inflammation and associated SLB desmitis, compared with injection of saline solution.
To compare soil concentrations of macrolide- and rifampicin-resistant Rhodococcus equi strains (MRRE) on horse-breeding farms that used thoracic ultrasonographic screening (TUS) to identify foals with subclinical pneumonia combined with subsequent administration of macrolides and rifampin to affected foals (TUS farms) versus soil concentrations on farms that did not (non-TUS farms), determine whether the combined use of TUS and antimicrobial treatment of subclinically affected foals was associated with soil concentration of MRRE, and assess whether there were temporal effects on soil concentrations of MRRE during the foaling season.
720 soil samples and 20 completed questionnaires from 20 horse-breeding farms (10 TUS farms and 10 non-TUS farms) in central Kentucky.
A questionnaire was used to gather information from participating farms about their 2019 foaling season. Soil samples were collected during January, March, May, and July 2019 for bacterial culture and antimicrobial susceptibility testing to identify any isolates of MRRE. Results were compared for TUS farms versus non-TUS farms. Linear mixed-effects modeling was used to evaluate for potential associations between the soil concentration of MRRE and the use of TUS.
Overall, the sum of the mean soil concentrations of MRRE was significantly higher for TUS farms (8.85 log10-transformed CFUs/g) versus non-TUS farms (7.37 log10-transformed CFUs/g).
CONCLUSIONS AND CLINICAL RELEVANCE
Our findings indicated that farms that use TUS to identify foals with subclinical pneumonia for antimicrobial treatment select for antimicrobial-resistant R equi strains. Because prognosis is worse for foals infected with resistant versus nonresistant strains of R equi, prudent use of antimicrobials to treat foals with subclinical pulmonary lesions attributed to R equi is recommended.
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 determine the pharmacokinetics of gallium maltolate (GaM) after intragastric administration in healthy foals.
Animals—6 healthy neonatal foals.
Procedures—Each foal received GaM (20 mg/kg) by intragastric administration. Blood samples were obtained before (time 0) and at 0.25, 0.5, 1, 2, 4, 8, 12, 24, 36, and 48 hours after GaM administration for determination of serum gallium concentrations by use of inductively coupled plasma mass spectroscopy.
Results—Mean ± SD pharmacokinetic variables were as follows: peak serum gallium concentration, 1,079 ± 311 ng/mL; time to peak serum concentration, 4.3 ± 2.0 hours; area under the serum concentration versus time curve, 40,215 ± 8,420 ng/mL/h; mean residence time, 39.5 ± 17.2 hours; area under the moment curve, 1,636,554 ± 931,458 ng([h]2/mL); and terminal half-life, 26.6 ± 11.6 hours. The mean serum concentration of gallium at 12 hours was 756 ± 195 ng/mL.
Conclusions and Clinical Relevance—Gallium maltolate administered via nasogastric tube at a dose of 20 mg/kg to neonatal foals resulted in gallium serum concentrations considered sufficient to suppress growth or kill Rhodococcus equi in macrophages and other infected tissues.
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 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 the importance of iron for
in vitro growth of Rhodococcus equi, define potential
iron sources in the environment and mechanisms by
which R equi may obtain iron from the environment,
and assess expression and immunogenicity of
Sample Population—10 virulent and 11 avirulent
strains of R equi.
Procedure—In vitro growth rates and protein patterns
of R equi propagated in media with normal,
excess, or limited amounts of available iron were
compared. Immunoblot analyses that used serum
from foals naturally infected with R equi and monoclonal
antibody against virulence-associated protein
(Vap)A were conducted to determine immunogenicity
and identity of expressed proteins.
Results—Excess iron did not alter growth of any
R equi strains, whereas growth of all strains was significantly
decreased in response to limited amounts
of available iron. Virulent R equi were able to use iron
from ferrated deferoxamine, bovine transferrin, and
bovine lactoferrin. Only virulent R equi expressed an
iron-regulated, immunogenic, surface-associated protein
identified as VapA.
Conclusions and Clinical Relevance—Iron is
required for the growth and survival of R equi.
Sources of iron for R equi, and mechanisms by which
R equi acquire iron in vivo, may represent important
virulence factors and novel targets for the development
of therapeutic and immunoprophylactic strategies
to control R equi infection in foals. Expression of
VapA is substantially upregulated when there is a limited
amount of available iron. (Am J Vet Res 2003;64:1337–1346)