Use of Serial Quantitative PCR of the vapA Gene of Rhodococcus equi in Feces for Early Detection of R. equi Pneumonia in Foals.
Abstract: Current screening tests for Rhodococcus equi pneumonia in foals lack adequate accuracy for clinical use. Real-time, quantitative PCR (qPCR) for virulent R. equi in feces has not been systematically evaluated as a screening test. Objective: The objective of this study was to evaluate the accuracy of qPCR for vapA in serially collected fecal samples as a screening test for R. equi pneumonia in foals. Methods: One hundred and twenty-five foals born in 2011 at a ranch in Texas. Methods: Fecal samples were collected concurrently with thoracic ultrasonography (TUS) screening examinations at ages 3, 5, and 7 weeks. Affected (pneumonic) foals (n = 25) were matched by age and date-of-birth to unaffected (n = 25) and subclinical (ie, having thoracic TUS lesions but no clinical signs of pneumonia) foals (n = 75). DNA was extracted from feces using commercial kits and concentration of virulent R. equi in feces was determined by qPCR. Results: Subsequently affected foals had significantly greater concentrations of vapA in feces than foals that did not develop pneumonia (unaffected and subclinical foals) at 5 and 7 weeks of age. Accuracy of fecal qPCR, however, was poor as a screening test to differentiate foals that would develop clinical signs of pneumonia from those that would remain free of clinical signs (including foals with subclinical pulmonary lesions attributed to R. equi) using receiver operating characteristic (ROC) methods. Conclusions: In the population studied, serial qPCR on feces lacked adequate accuracy as a screening test for clinical R. equi foal pneumonia.
Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.
Publication Date: 2016-01-24 PubMed ID: 26806422PubMed Central: PMC4913589DOI: 10.1111/jvim.13828Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research paper discusses a study that evaluated the accuracy of a diagnostic method called PCR (Polymerase Chain Reaction) in detecting Rhodococcus equi pneumonia in young horses (foals). The method involved repeatedly testing fecal samples in a quantitative manner. However, the results indicated the method did not have enough precision to be successfully used as a diagnostic screening tool.
Background and Objective
- The study aimed at determining the accuracy of quantitative PCR (qPCR) as a screening test for Rhodococcus equi pneumonia in foals, a disease that severely affects the respiratory health in young horses.
- Previously, qPCR technology hasn’t been systematically evaluated to identify virulent R. equi in feces. Hence, the objective of this study was to determine the effectiveness of this method in diagnosing this pneumonia using fecal samples.
Methodology
- A total of 125 foals born in 2011 at a Texas ranch were enrolled in the study.
- Fecal samples were obtained during thoracic ultrasonography (TUS) screening examinations when the foals were 3, 5, and 7 weeks old.
- The foals were categorized into three groups – affected (pneumonic) foals (25), unaffected foals (25), and subclinical foals (75), the latter displaying thoracic TUS lesions but no clinical signs of pneumonia.
- The DNA was extracted from feces using commercial kits, and the concentration of virulent R. equi was determined using qPCR.
Results
- At 5 and 7 weeks of age, the concentrations of vapA, a gene of R. equi, in the feces of subsequently affected foals were significantly higher compared to foals who did not develop pneumonia.
- However, the accuracy of fecal qPCR as a screening test to distinguish between foals that would eventually show symptoms of pneumonia and those that would remain free from clinical signs was poor.
Conclusions
- Overall, the study concluded that qPCR on serial feces samples was not sufficiently accurate as a screening test for clinical Rhodococcus equi pneumonia in foals in the studied population.
Cite This Article
APA
Madrigal RG, Shaw SD, Witkowski LA, Sisson BE, Blodgett GP, Chaffin MK, Cohen ND.
(2016).
Use of Serial Quantitative PCR of the vapA Gene of Rhodococcus equi in Feces for Early Detection of R. equi Pneumonia in Foals.
J Vet Intern Med, 30(2), 664-670.
https://doi.org/10.1111/jvim.13828 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
- Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
- Laboratory of Veterinary Epidemiology and Economics, Faculty of Veterinary Medicine, Warsaw University of Life Sciences, Warsaw, Poland.
- Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
- Equine Division, 6666 Ranch, Guthrie, TX.
- Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
- Department of Large Animal Clinical Sciences, College of Biomedical Sciences and Veterinary Medicine, Texas A&M University, College Station, TX.
MeSH Terms
- Actinomycetales Infections / diagnosis
- Actinomycetales Infections / microbiology
- Actinomycetales Infections / veterinary
- Animals
- Bacterial Proteins / isolation & purification
- Feces / microbiology
- Horse Diseases / diagnosis
- Horse Diseases / microbiology
- Horses
- Pneumonia, Bacterial / diagnosis
- Pneumonia, Bacterial / microbiology
- Pneumonia, Bacterial / veterinary
- Polymerase Chain Reaction / methods
- Polymerase Chain Reaction / veterinary
- Rhodococcus equi / isolation & purification
- Sensitivity and Specificity
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