A commercial rapid-absorbed ELISA developed to detect antibodies to Mycobacterium paratuberculosis in bovine serum was modified for use with goat serum. Diagnostic sensitivity was evaluated, using a group of 163 goats from a herd with endemic paratuberculosis. Blood and fecal samples were obtained simultaneously, and prevalence of shedding of M paratuberculosis in the feces was estimated by detection of DNA of the mycobacterial insertion sequence, IS900, using a commercial test kit. Diagnostic specificity was evaluated, using blood samples from a total of 123 goats in 10 herds that were considered clinically free of paratuberculosis. The IS900 DNA was detected in 35 of the 163 goats (21%) from the infected herd. Serum antibody to M paratuberculosis was detected in 19 of the 35 IS900 DNA-positive goats, for apparent sensitivity of 54%. Serum antibody was detected in 18 of the 128 IS900 DNA-negative goats from the infected herd. Negative results for serum antibody to M paratuberculosis were obtained for all 123 goats from the herds that were considered clinically free of paratuberculosis.

An ELISA was developed to detect antibodies to the 41-kd flagellin (P41) of Borrelia burgdorferi in serum obtained from cattle. Absorption studies, immunoblot analysis, immunoelectron microscopy, and correlation of results of the P41-ELISA and the P39-ELISA as well as measurement of the antibody to P41 in calves challenge-exposed with Borrelia theileri were used to assess the specificity of the P41-ELISA. Antigens derived from Escherichia coli, Leptospira interrogans serovar hardjo, and B burgdorferi were used for absorption studies and immunoblot analysis. Antibodies to P41 of B burgdorferi cross-reacted with antigens of E coli, but were not cross-reactive with L hardjo. A value 3 SD higher than the mean of the negative-control population of cattle was defined as the minimum value cutoff value) for a positive result by the P41-ELISA. Use of this value for classification of test results reduced the predicted rate of false-positive results attributable to E coli cross-reactivity to 1%. Immunoblot analysis revealed that test-positive serum from cattle reacted mainly with 41-, 39-, 34-, and 31-kd proteins of B burgdorferi, as well as several smaller proteins. Immunoelectron microscopy revealed that serum from cattle that was test-positive by the P41-ELISA bound to the flagellin and outer membrane of B burgdorferi. Results of absorption studies, immunoblot analysis, and immunoelectron microscopy were correlated and indicated that serum from cattle that was test-positive by P41-ELISA had stronger reactivity to B burgdorferi antigens than to antigens of E coli or L hardjo. The concentrations of antibodies measured by P41-ELISA and P39-ELISA testing were highly correlated [R(2)=0.78]. Calves challenge-exposed with B theileri also had test-positive results by the P-41-ELISA as early as 2 weeks after exposure, but serum antibody concentrations decreased to prechallenge-exposure concentrations by 9 weeks after exposure.