Evidence for a high rate of false-positive results with the indirect fluorescent antibody test for Ehrlichia risticii antibody in horses.
Abstract: The original objective was to determine seroprevalence of Ehrlichia risticii antibody among horses in California. On the basis of the unexpected results of the survey, an investigation into the accuracy and reproducibility of results of the indirect fluorescent antibody (IFA) test for E risticii was carried out. Methods: Prospective, seroprevalence study. Methods: Healthy horses (n = 655) and horses with clinical signs of equine monocytic ehrlichiosis (EME; n = 514) from various regions of California. Methods: The IFA test was performed. Results were compared with results of an ELISA and with results of western immunoblot analysis. Results: Overall, 104 of 655 (15.9%) healthy horses had evidence of an antibody response. However, 84 of 514 (16.3%) horses with clinical signs of EME also had positive test results, and of the 8 seropositive diseased horses for which paired (acute and convalescent) samples had been submitted, only 1 had a rise in antibody titers between the acute and convalescent samples. Comparison of results for the IFA test, ELISA, and western immunoblot analysis revealed a high rate of false-positive results for the IFA test. Subsequent studies suggested that routine vaccination of horses with non-E risticii vaccines may have contributed to the false-positive reactions. Conclusions: The data failed to provide conclusive evidence of E risticii infection among California horses. Owing to the high percentage of false-positive test results, caution is advised when using the IFA test to diagnose EME in horses or to determine the necessity for E risticii vaccination.
Publication Date: 1995-12-01 PubMed ID: 7493874
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research examines the prevalence of the Ehrlichia risticii antibody in horses in California and discovers high rates of false positives in test results due to the indirect fluorescent antibody (IFA) test, suggesting caution in its use for diagnosing equine monocytic ehrlichiosis (EME) and in determining the need for E risticii vaccinations.
Objectives and Methodology
- The initial goal of this study was to find out the seroprevalence, or the level of a pathogen in a population as measured in blood serum, of Ehrlichia risticii antibody in horses in California.
- Unexpected results from the survey sparked an examination into the accuracy and dependability of the IFA test for E risticii.
- The researchers conducted a prospective seroprevalence study, examining both healthy horses (n=655) and those showing clinical signs of EME (n=514) from various regions of the state.
- The IFA test was applied, with the results weighed against those derived from an enzyme-linked immunosorbent assay (ELISA) and Western immunoblot analysis – laboratory methods for detecting specific protein molecules.
Key Findings
- Out of the healthy horses tested, 15.9% showed evidence of an antibody response. Similarly, 16.3% horses showing symptoms of EME had positive test results.
- However, of the eight seropositive diseased horses which had both acute and convalescent samples tested, only one revealed a rise in antibody titer between the acute and convalescent samples, hinting towards detection inconsistencies.
- The comparison of the IFA test results with the ELISA and Western immunoblot analysis showed a considerable number of false positives produced by the IFA test.
- Further investigations implied that regular vaccination of horses with non-E risticii vaccines could intensify false-positive reactions.
Conclusion and Recommendations
- The research failed to provide solid proof of E risticii infection among horses in California.
- The significant number of false-positive results identified necessitates caution when using the IFA test to diagnose EME or determine the need for E risticii vaccination in horses.
Cite This Article
APA
Madigan JE, Rikihisa Y, Palmer JE, DeRock E, Mott J.
(1995).
Evidence for a high rate of false-positive results with the indirect fluorescent antibody test for Ehrlichia risticii antibody in horses.
J Am Vet Med Assoc, 207(11), 1448-1453.
Publication
Researcher Affiliations
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
MeSH Terms
- Animals
- Antibodies, Bacterial / blood
- Blotting, Western
- California / epidemiology
- Cell Line
- Ehrlichia / immunology
- Ehrlichiosis / epidemiology
- Ehrlichiosis / immunology
- Ehrlichiosis / veterinary
- False Positive Reactions
- Fluorescent Antibody Technique, Indirect / standards
- Horse Diseases / epidemiology
- Horse Diseases / immunology
- Horses
- Mice
- Prevalence
- Prospective Studies
- Reproducibility of Results
- Seroepidemiologic Studies
- Vaccination / veterinary
Citations
This article has been cited 14 times.- Thirumalapura NR, Livengood J, Beeby J, Wang W, Goodrich EL, Goodman LB, Erol E, Tewari D. Improved molecular detection of Neorickettsia risticii with a duplex real-time PCR assay in the diagnosis of Potomac horse fever. J Vet Diagn Invest 2023 Jan;35(1):62-66.
- Teymournejad O, Lin M, Bekebrede H, Kamr A, Toribio RE, Arroyo LG, Baird JD, Rikihisa Y. Isolation and Molecular Analysis of a Novel Neorickettsia Species That Causes Potomac Horse Fever. mBio 2020 Feb 25;11(1).
- Shaw SD, Stämpfli H. Diagnosis and Treatment of Undifferentiated and Infectious Acute Diarrhea in the Adult Horse. Vet Clin North Am Equine Pract 2018 Apr;34(1):39-53.
- Durán MC, Marqués FJ. Detection of Neorickettsia risticii, the agent of Potomac horse fever, in a Gypsy Vanner stallion from Manitoba. Can Vet J 2016 Mar;57(3):293-5.
- Greiman SE, Tkach VV, Pulis E, Fayton TJ, Curran SS. Large scale screening of digeneans for Neorickettsia endosymbionts using real-time PCR reveals new Neorickettsia genotypes, host associations and geographic records. PLoS One 2014;9(6):e98453.
- Baird JD, Arroyo LG. Historical aspects of Potomac horse fever in Ontario (1924-2010). Can Vet J 2013 Jun;54(6):565-72.
- Lin M, Zhang C, Gibson K, Rikihisa Y. Analysis of complete genome sequence of Neorickettsia risticii: causative agent of Potomac horse fever. Nucleic Acids Res 2009 Oct;37(18):6076-91.
- Heller MC, McClure J, Pusterla N, Pusterla JB, Stahel S. Two cases of Neorickettsia (Ehrlichia) risticii infection in horses from Nova Scotia. Can Vet J 2004 May;45(5):421-3.
- Pusterla N, Madigan JE, Chae JS, DeRock E, Johnson E, Pusterla JB. Helminthic transmission and isolation of Ehrlichia risticii, the causative agent of Potomac horse fever, by using trematode stages from freshwater stream snails. J Clin Microbiol 2000 Mar;38(3):1293-7.
- Barlough JE, Reubel GH, Madigan JE, Vredevoe LK, Miller PE, Rikihisa Y. Detection of Ehrlichia risticii, the agent of Potomac horse fever, in freshwater stream snails (Pleuroceridae: Juga spp.) from northern California. Appl Environ Microbiol 1998 Aug;64(8):2888-93.
- Reubel GH, Barlough JE, Madigan JE. Production and characterization of Ehrlichia risticii, the agent of Potomac horse fever, from snails (Pleuroceridae: Juga spp.) in aquarium culture and genetic comparison to equine strains. J Clin Microbiol 1998 Jun;36(6):1501-11.
- Ravyn MD, Goodman JL, Kodner CB, Westad DK, Coleman LA, Engstrom SM, Nelson CM, Johnson RC. Immunodiagnosis of human granulocytic ehrlichiosis by using culture-derived human isolates. J Clin Microbiol 1998 Jun;36(6):1480-8.
- Dutta SK, Vemulapalli R, Biswas B. Association of deficiency in antibody response to vaccine and heterogeneity of Ehrlichia risticii strains with Potomac horse fever vaccine failure in horses. J Clin Microbiol 1998 Feb;36(2):506-12.
- Mott J, Rikihisa Y, Zhang Y, Reed SM, Yu CY. Comparison of PCR and culture to the indirect fluorescent-antibody test for diagnosis of Potomac horse fever. J Clin Microbiol 1997 Sep;35(9):2215-9.
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