Foot-and-Mouth Disease: The Agar Gel Diffusion Precipitin Test for Antibody to Virus-Infection-Associated (Via) Antigen as a Tool for Epizootiologic Surveys1

McVicar, J. W. (Plum Island Animal Disease Lab., U. S. Dept. of Agriculture, P.O. Box 848, Greenport, N. Y. 11944) and P. Sutmoller. Foot-and-mouth disease: The agar gel diffusion precipitin test for antibody to virus-infection-associated (VIA) antigen as a tool for epizootiologic surveys. Amer. J. Epid., 1970, 92; 273–278.—Sera from animals with well-documented pre- and postexposure histories were used for a retrospective study to evaluate the agar gel diffusion precipitin (AGDP) test as a method of detecting antibody to VIA antigen. Sera of all but 2 of 304 animals (cattle, sheep, goats, and pigs) obtained before exposure to live virus were negative. One vaccinated and one passively immunized steer had weakly positive reactions. When non-immunized animals become infected, 80–90% had positive reactions 3–4 weeks postexposure. Some of these animals were followed for 12 weeks after infection and all continued to have either positive or weakly positive reactions. A few sheep had positive reactions for 19 months. Sera were tested from vaccinated cattle which became infected following exposure to live virus. Cattle immunized with a vaccine produced from tissue culture virus, adsorbed to aluminum hydroxide gel and inactivated with formalin, developed positive reactions following infection comparable to those of non-im-munized animals. Cattle immunized with a tissue culture virus inactivated with acetylethyleneimine and mixed with modified Freund's adjuvant had consistently weaker and shorter-lived positive reactions after infection.