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Abstract

Objective—To evaluate a real-time quantitative polymerase chain reaction (QPCR) assay in the detection and quantitation of virulent Rhodococcus equi.

Sample Population—1 virulent, 2 intermediately virulent, and 2 avirulent strains of R equi and 16 isolates of bacteria genetically related to R equi.

Procedure—The QPCR assay was evaluated for detection and quantitation of the virulence-associated gene (vapA) of R equi in pure culture and in samples of tracheobronchial fluid, which were inoculated with known numbers of virulent R equi. Results were compared with those derived via quantitative microbial culture and standard polymerase chain reaction methods.

Results—The QPCR assay detected the vapAgene in pure culture of R equi and in tracheobronchial fluid samples that contained as few as 20 CFUs of virulent R equi/mL and accurately quantitated virulent R equi to 103 CFUs/mL of fluid. The assay was highly specific for detection of the vapA gene of virulent R equi and was more sensitive than standard polymerase chain reaction for detection of R equi in tracheobronchial fluid.

Conclusions and Clinical Relevance—The QPCR assay appears to be a rapid and reliable method for detecting and quantitating virulent R equi. The accuracy of the QPCR assay is comparable to that of quantitative microbial culture. The increased sensitivity of the QPCR method in detection of virulent R equi should facilitate rapid and accurate diagnosis of R equi pneumonia in foals. (Am J Vet Res 2005;66:755–761)

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in American Journal of Veterinary Research

Abstract

Objective—To characterize the temporality of dates of breeding and abortion classified as mare reproductive loss syndrome (MRLS) among mares with abortions during early gestation.

Animals—2,314 mares confirmed pregnant at approximately 28 days after breeding from 36 farms in central Kentucky, including 515 mares that had earlyterm abortions.

Procedure—Farm veterinarians and managers were interviewed to obtain data for each mare that was known to be pregnant to determine pregnancy status, breeding date, last date known to be pregnant, and date of abortion.

Results—Mares bred prior to April 1, 2001, appeared to be at greatest risk of early-term abortion, both among and within individual farms. Mares bred in mid-February appeared to be at greatest risk of abortion, with an estimated weekly incidence rate of abortion of 66% (95% CI, 52% to 80%).

Conclusions and Clinical Relevance—Mares in central Kentucky bred between mid-February and early March were observed to be at greatest risk of early-term abortion, and risk gradually decreased to a background incidence of abortion of approximately 11%. Mares bred after April 1, 2001, appeared to be at markedly less risk, indicating that exposure to the cause of MRLS likely occurred prior to this date. (Am J Vet Res 2005;66:1792–1797)

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in American Journal of Veterinary Research

Abstract

Objective—To estimate spatial risks associated with mare reproductive loss syndrome (MRLS) during 2001 among horses in a specific study population and partition the herd effects into those attributable to herd location and those that were spatially random and likely attributable to herd management.

Animals—Pregnant broodmares from 62 farms in 7 counties in central Kentucky.

Procedure—Veterinarians provided the 2001 abortion incidence proportions for each farm included in the study. Farms were georeferenced and data were analyzed by use of a fully Bayesian risk-mapping technique.

Results—Large farm-to-farm variation in MRLS incidence proportions was identified. The farm-to-farm variation was largely attributed to spatial location rather than to spatially random herd effects

Conclusions and Clinical Relevance—Results indicate that there are considerable data to support an ecologic cause and potential ecologic risk factors for MRLS. Veterinary practitioners with more detailed knowledge of the ecology in the 7 counties in Kentucky that were investigated may provide additional data that would assist in the deduction of the causal factor of MRLS via informal geographic information systems analyses and suggest factors for inclusion in further investigations. (Am J Vet Res 2005;66:17–20)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate the correlation between halftime of liquid-phase gastric emptying (T50), determined with nuclear scintigraphy using technetium Tc 99m pentetate, and absorption variables of orally administered acetaminophen.

Animals—6 mature horses.

Procedure—Technetium Tc 99m pentetate (10 mCi) and acetaminophen (20 mg/kg of body weight) were administered simultaneously in 200 ml of water. Serial left and right lateral images of the stomach region were obtained with a gamma camera, and T50 determined separately for counts obtained from the left side, the right side and the geometric mean. Power exponential curves were used for estimation of T50 and modified R2 values for estimation of goodness of fit of the data. Serial serum samples were taken, and acetaminophen concentration was determined, using fluorescence polarization immunoassay. Maximum serum concentration (Cmax), time to reach maximum serum concentration (Tmax), area under the curve for 240 minutes and the absorption constant (Ka) were determined, using a parameter estimation program. Correlations were calculated, using the Spearman rank correlation coefficient.

Results—Correlations between T50 and Tmax and between T50 and Ka were significant.

Conclusions and Clinical Relevance—Tmax and Ka are valuable variables in the assessment of liquidphase gastric emptying using acetaminophen absorption. Acetaminophen absorption may be a valuable alternative to nuclear scintigraphy in the determination of gastric emptying rates in equine patients with normally functioning small intestine. (Am J Vet Res 2000;61:310–315)

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in American Journal of Veterinary Research

Abstract

Objective—To determine whether administration of killed West Nile virus vaccine was associated with pregnancy loss among broodmares.

Design—Retrospective cohort study.

Animals—595 mares.

Procedure—Records of pregnant mares with known vaccination history from 4 farms were reviewed. Information obtained from 595 mares included mare's identification; farm; age; breed; reproductive status; last breeding date; date last known pregnant; vaccination date; age of conceptus at vaccination; vaccination during the early embryonic, early fetal, and late fetal periods; and whether an early embryonic death (EED), early fetal loss (EFL), or late fetal loss (LFL) occurred. The relationships between the dichotomous outcomes of loss (eg, EED, EFL, LFL) and independent categoric variables (eg, vaccination during the early embryonic, early fetal, or late fetal periods) were examined.

Results—Vaccination of pregnant mares during any period of gestation was not associated with increased incidence of pregnancy loss.

Conclusions and Clinical Relevance—Many mares are already pregnant at the onset of mosquito season, when mares are more likely to be vaccinated than at other times. Our findings provide evidence that vaccine administration will not compromise pregnancy in horses. (J Am Vet Med Assoc 2004;225:1894–1897)

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in Journal of the American Veterinary Medical Association

Abstract

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.

Animals—26 foals.

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)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine factors associated with development of postoperative ileus (POI) in horses undergoing surgery for colic.

Design—Prospective case-control study.

Animals—251 horses undergoing colic surgery, of which 47 developed POI.

Procedure—Signalment, history, clinicopathologic data, pre- and postoperative treatments, lesions, complications, costs, and outcome were recorded for all horses during hospitalization.

Results—Variables associated with increased odds of POI included small intestinal lesion, high PCV, and increased duration of anesthesia. There was modest evidence that pelvic flexure enterotomy and intraoperative administration of lidocaine may have reduced the odds of developing POI.

Conclusions and Clinical Relevance—Findings during the preoperative and intraoperative periods can be used to identify horses at increased risk of POI. Reducing surgical and anesthetic duration should decrease the incidence of POI. ( J Am Vet Med Assoc 2004;225: 1070–1078)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify factors significantly associated with an epidemic of fibrinous pericarditis during spring 2001 among horses in central Kentucky.

Design—Case-control study.

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 Assoc 2003;223:832–838)

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in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE

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.

SAMPLES

720 soil samples and 20 completed questionnaires from 20 horse-breeding farms (10 TUS farms and 10 non-TUS farms) in central Kentucky.

PROCEDURES

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.

RESULTS

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.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify factors associated with abortions of mares during late gestation attributed to mare reproductive loss syndrome (MRLS).

Design—Case-control study.

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 MRLS.

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 (MRLS-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)

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in Journal of the American Veterinary Medical Association