Sensitivity and Specificity of the Indirect Fluorescent Antibody Test in the Study of Four Murine Coccidia1

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Abstract
The sensitivity and specificity of the indirect fluorescent antibody (IFA) test for the detection of serum antibodies were examined in mice that were infected with Eimeria falciformis, E. ferrisi, E. papillata or E. vermiformis. For the study of each species, 5 groups of mice were given graded inoculation doses of 10, 102, 103, 104 or 105 sporulated oocysts in a primary infection. The 6th group was infected with 3 sequential doses of 1.5 .times. 103, 1.5 .times. 104 and 1.5 .times.105 sporulated oocysts per mouse at 2- to 3-wk intervals. All groups of infected mice developed serum antibodies. Sera were titrated by the IFA test with purified sporozoites. Strong fluorescence and high IFA titers were observed with homologous reactions mainly with the sera from mice infected with the higher inoculation dose levels in primary infections and from those given 3 sequential inoculation doses. Immunological cross reaction among the 4 spp. of Eimeria occurred at dilutions of 1:10 to 1:160. Very weak or no fluorescence of free sporozoites was observed with sera from noninfected mice, and there was no fluorescence of sporozoites contained in intact sporocytes.