Comparison of a Serum Indirect Fluorescent Antibody Test with Two Western Blot Tests for the Diagnosis of Equine Protozoal Myeloencephalitis

Abstract

Abstract.A serum indirect fluorescent antibody test (IFAT) was compared with a Western blot (WB) and a modified Western blot (mWB) for diagnosis of equine protozoal myeloencephalitis (EPM). Using receiveroperating characteristic (ROC) analysis, the area under the curve of the IFAT was greater than the area under the curves of the WB and the mWB (P ϭ 0.025 and P ϭ 0.044, respectively). There was no statistically significant difference between the areas under the curves of the WBs (P Ͼ 0.05). On the basis of an arbitrarily chosen cut-off titer for a positive test result of 1:80 for the IFAT and interpreting weak positive WB results as positive test results, the sensitivities and 95% confidence intervals (CI) of all 3 tests were identical and equal to 88.9% (51.8-99.7%). The specificities and 95% CIs of the IFAT, WB, and mWB test were 100% (91-100%), 87.2% (72.6-95.7%), and 69.2% (52.4-83%), respectively. The overall accuracy of the IFAT was shown to be better than that of the WBs and, therefore, the test has potential for use in the diagnosis of EPM caused by Sarcocystis neurona.Equine protozoal myeloencephalitis (EPM) is a common neurological disease of horses in North America. 13,19 Sarcocystis neurona and Neospora hughesi are the protozoal parasites associated with EPM; 7,17 however, serologic surveys have indicated that exposure to S. neurona is more frequent. [1][2][3]21,26,27 The seroprevalence of S. neurona in US horses has been estimated to be between 34% and 60% in different parts of the country. 1,2,21,23,26,27 The Western blot (WB) test has been the standard diagnostic test used for serologic surveys and for the diagnosis of clinically suspected EPM, caused by S. neurona. The WB detects specific IgG antibodies in serum and spinal fluid (CSF) of horses infected or exposed to the parasite. 10 The overall sensitivity and specificity of the WB in CSF were estimated to be 87% and 56%, respectively. 5 In serum, the WB sensitivity and specificity were estimated as 80% and 38%, respectively, for horses with neurologic signs, and 88% and 56%, respectively, for horses without neurologic signs. 5 The low specificity of the test makes interpretation of a serologic positive test result difficult. To date, a negative WB test result on serum is

Prevalence of antibodies against Neospora spp. and Sarcocystis neurona in donkeys from northeastern Brazil

“…Immunoblot is considered the golden test for seroprevalence studies of S. neurona in horses, but it is expensive and laborious. DUARTE et al (2003) showed that IFAT could be an alternative to immunoblot for S. neurona antibody detection in horses, with good specificity and sensitivity. Cross-reactivity of both tests with other protozoa from donkeys is not known.…”

Experimental Infection of Ponies With Sarcocystis Fayeri and Differentiation From Sarcocystis Neurona Infections in Horses

“…† Sarcocystis neurona agglutination test ). ‡ Indirect immunofluorescence antibody test (Duarte et al, 2003). killed, serum and CSF samples of all ponies were collected.…”

“…Originally, a Western blot analysis was developed to detect antibodies to S. neurona in horses, which was reported to be able to differentiate between S. neurona and S. fayeri (Granstrom et al, 1993). Recently, another group of scientists reported that the Western blot analysis for S. neurona antibodies did not perform as well as an indirect immunofluorescence antibody test (IFAT) (Duarte et al, 2003).…”

Equine Protozoal Myeloencephalitis: An Updated Consensus Statement with a Focus on Parasite Biology, Diagnosis, Treatment, and Prevention

“…Descriptions of testing options and reported test performance are shown in Table 1 71, 72, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93. All tests can be performed on serum or CSF, and none is considered a gold standard.…”