A MODIFIED AGGLUTINATION-TEST FOR NEOSPORA-CANINUM - DEVELOPMENT, OPTIMIZATION, AND COMPARISON TO THE INDIRECT FLUORESCENT-ANTIBODY TEST AND ENZYME-LINKED-IMMUNOSORBENT-ASSAY

Current serologic tests used to detect antibodies to Neospora caninum require species-specific secondary antibodies, limiting the number of species that can be tested. In order to examine a wide variety of anim al species that may be infected with N. caninum, a modified direct agg lutination test (N-MAT) similar to the Toxoplasma gondii modified dire ct agglutination test (T-MAT) was developed. This test measures the di rect agglutination of parasites by N. caninum-specific antibodies in s erum, thus eliminating the need for secondary host-specific anti-isoty pe sera. The N-MAT was compared to the indirect fluorescent-antibody t est (IFAT) and the enzyme-linked immunosorbent assay (ELISA) with a '' gold standard'' serum panel from species for which secondary antibodie s were available (n = 547). All positive samples tested were from anim als with histologically confirmed infections. Up to 16 different speci es were tested. The N-MAT gave a higher sensitivity (100%) and specifi city (97%) than the ELISA (74 and 93%, respectively) and had a higher sensitivity but a lower specificity than the IFAT (98 and 99%, respect ively). The reduced specificity of the N-MAT was due to false-positive reactions in testing fetal fluids with particulate matter or severely hemolyzed serum. Overall, the N-MAT proved to be highly sensitive and specific for both naturally and experimentally infected animals, high ly reproducible between and within readers, easy to use on large sampl e sizes without requiring special equipment, and useful in testing ser um from any species without modification.