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Objective: To investigate 1) the cut-off titers of
antitoxoplasma antibodies through in IgG- ELISA and IFA
tests and 2) application of IgG- ELISA rather than IFA test for
diagnosis of toxoplasmosis (Toxoplasma gondii) in mature
sheep.
Animals: One hundred and ten Iranian mature sheep.
Procedure: The serum samples were examined to determine
the final positive dilution of antitoxoplasma antibody by IgG- ELISA and IFA tests. For this purpose, immunoreactivity of
the final positive dilution of each serum with to SAG-i antigen was determined by western blot analysis. The ELISA
microplate coated with 105 tachyzoites/ well, was incubated
with diluted sheep sera. After adding of substrate, enzymatic
activity was measured at 492 nm. Samples with higher
absorbance values (= 2.5 times greater than these values of
negative controls) designated as positive.The data obtained
from 110 sera with WA and FLISA was compared with each
other to determine the percentage of agreement between them.
Statistical analysis: Using a chi-square test to show the
significant differences between results of IFA and ELISA. Furthermore, these results were compared to determine the percentage of agreement between them.
Results: 24 out of 110 serum samples were concordant
positive (21.8%) and 79 cases (70.9%) were concordant
negative in both IFA and ELISA. All positive samples exhibited strong reactivity to SAG-i (30 KD band). Among
110 serum samples, five discordant ELISA- positive and two
discordant IFA- positive sera had no reactivity with SAG-i
band in WB. Moreover, there is 92.7% coincidence between
results of ELISA and WA tests.
Conclusion: In this study the lowest valuable titer, for
detection of Toxoplasmosis in, sheep, was obtained as 1:40
and 1:100 in the IFA and ELISA tests, respectively.
Furthermore, immunoreactivity of serum dilutions to SAG- lantigen in the WB proved to be a useful tool for setting of
optimum cut-off titers in the IFA and ELISA tests.
J.Fac. Vet.Med. Univ. Tehran. 60,3:219-223,2005.