Theoretical aspects of the enzyme-linked immunosorbent assay technique and its use in the detection of Cowdria ruminantium antigen and antibody in reacting animals.

Numerous parameters affect the enzyme-linked immunosorbent assay activity and the assay conditions must therefore be carefully controlled to obtain reproducible results. These parameters include temperature, pH, ionic strength, buffer composition, cofactors, substrate depletion, product inhibition, increasing reversal of reaction as product concentration increases, adsorption of enzyme to solid supports, denaturation and non-enzymatic background rate. An ELISA was used to detect Cowdria ruminantium antibodies during the course of heartwater disease. IgM antibodies reached a maximum on the 4th day after infection and disappeared on the 7th day. IgG antibodies first appeared on the 8th day and continued to increase during the remainder of the observation period of 28 days. The presence of C. ruminantium in the blood fractions of diseased animals was demonstrated by an enzyme-linked immunosorbent assay. The earliest detection of C. ruminantium antigen was in plasma and serum on the 4th day after inoculation. Of all the blood fractions investigated, the red blood cell fraction showed the highest concentration and this reached a maximum on the 12th day after infection.