Evaluation and comparison of an indirect fluorescent ...
|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|
|Author(s)||P. C. Duarte, B. M. Daft, P. A. Conrad, A. E. Packham, W. J. Saville, R. J. MacKay, B. C. Barr, W. D. Wilson, T. Ng, S. M. Reed, I. A. Gardner|
|Journal||Journal of Parasitology|
|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 titres, and to determine the effect of S. neurona vaccination on the diagnosis of infection. 110 horses with or without neurological disease submitted for necropsy to the California Animal Health and Food Safety Laboratory System, California, USA, between 1996 and 1999 were enrolled in the study. 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. Titre-specific likelihood ratios (LRs) ranged from 0.03 to 187.8 for titres between <10 and 640. Median time to conversion was 22-26 days postinfection (DPI) in serum and 30 DPI in CSF. The correlation between serum and CSF titres was moderately strong (r=0.6) at 30 DPI. The percentage of vaccinated antibody-positive horses ranged from 0 to 95% between 0 and 112 days after the second vaccination. It is concluded that IFAT is reliable and accurate using serum and CSF. Use of LRs potentially improves clinical decision making. Correlation between serum and CSF titres affects the joint accuracy of the IFAT; therefore, the ratio of serum to CSF titres has potential diagnostic value. The S. neurona vaccine could possibly interfere with equine protozoal myeloencephalitis diagnosis.|
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