Primary immunoglobulin response of herons to infection with Venezuelan encephalitis virus.

Seven to nine days after inoculation with a replicating antigen, Venezuelan encephalitis virus, hemagglutination-inhibiting antibodies were present in plasma of 18 to 20 black-crowned night herons (BCNH), 14 of 15 great egrets (ge) , and 7 of 7 snowy egrets (SE). 19S (immunoglobulin M) precedes 7S (immunoglobulin G) antibodies in all but one bird of six GE, six SE, and six BCNH. 19S antibodies were detected for only 2 to 4 weeks post-inoculation. The induction period for both types of antibody was prolonged by 2 to 6 days as compared with earlier studies in gallinaceous birds using nonreplicating antigens. A marked delay in reaching peak titer of 7S antibodies was also observed. Hemagglutination inhibition tests were nearly as sensitive as neutralization tests for detecting 19S and early 7S antibodies. Size of virus inoculum did not measurably affect time of induction or titer of antibodies.