title: Evaluation and comparison of an indirect fluorescent antibody test for detection of antibodies to Sarcocystis neurona, using serum and cerebrospinal fluid of naturally and experimentally infected, and vaccinated horses.
abstract: The objectives of this study were to evaluate the accuracy of the indirect fluorescent antibody test (IFAT) using serum and cerebrospinal fluid (CSF) of horses naturally and experimentally infected with Sarcocystis neurona, to assess the correlation between serum and CSF titers, and to determine the effect of S. neurona vaccination on the diagnosis of infection. Using receiver-operating characteristic analysis, the areas under the curve for the IFAT were 0.97 (serum) and 0.99 (CSF). Sensitivity and specificity were 83.3 and 96.9% (serum, cutoff 80) and 100 and 99% (CSF, cutoff 5), respectively. Titer-specific likelihood ratios (LRs) ranged from 0.03 to 187.8 for titers between <10 and 640. Median time to conversion was 22-26 days postinfection (DPI) (serum) and 30 DPI (CSF). The correlation between serum and CSF titers was moderately strong (r = 0.6) at 30 DPI. Percentage of vaccinated antibody-positive horses ranged from 0 to 95% between 0 and 112 days after the second vaccination. Thus, the IFAT was reliable and accurate using serum and CSF. Use of LRs potentially improves clinical decision making. Correlation between serum and CSF titers affects the joint accuracy of the IFAT; therefore, the ratio of serum to CSF titers has potential diagnostic value. The S. neurona vaccine could possibly interfere with equine protozoal myeloencephalitis diagnosis.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, One Shields Avenue, Davis, California 95616, USA. pdduarte@ucdavis.edu
authors.forename: Paulo C
authors.initials: PC
authors.lastname: Duarte
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Daft
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Conrad
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Packham
authors.forename: William J
authors.initials: WJ
authors.lastname: Saville
authors.forename: Robert J
authors.initials: RJ
authors.lastname: MacKay
authors.forename: Bradd C
authors.initials: BC
authors.lastname: Barr
authors.forename: W David
authors.initials: WD
authors.lastname: Wilson
authors.forename: Terry
authors.initials: T
authors.lastname: Ng
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Reed
authors.forename: Ian A
authors.initials: IA
authors.lastname: Gardner
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood* / Q000134:cerebrospinal fluid*; D004679:Encephalomyelitis / Q000175:diagnosis / Q000469:parasitology / Q000662:veterinary; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary*; D006734:Horse Diseases / Q000097:blood / Q000134:cerebrospinal fluid / Q000276:immunology*; D006736:Horses; D016013:Likelihood Functions; D008297:Male; D016052:Protozoan Vaccines / Q000276:immunology; D012372:ROC Curve; D015203:Reproducibility of Results; D012522:Sarcocystis / Q000276:immunology*; D012523:Sarcocystosis / Q000097:blood / Q000134:cerebrospinal fluid / Q000276:immunology / Q000662:veterinary*; D012680:Sensitivity and Specificity; D014611:Vaccination / Q000662:veterinary
chemical_list: D000913:Antibodies, Protozoan; D016052:Protozoan Vaccines