Incidence of antibody for hemagglutinating encephalomyelitis virus in serums from swine in the United States.

Serums prepared from blood collected from swine in Arizona, Florida, Georgia, Hawaii, Iowa, Maine, New Hampshire, Oregon, Vermont, and Washington were examined by the hemagglutination-inhibition (HI) test for antibody to hemagglutinating encephalomyelitis virus (HEV). Antibody was detected in serums from swine in each of the states except Maine, New Hampshire, and Vermont. The frequency of antibody ranged from 10.9% (6 of 55) with serums from swine in Oregon, to 98.6% (71 of 72) with serums from sows in Iowa. A total of 1,241 serums (438 from hysterectomy-derived, colostrum-deprived, neonatal pigs and 803 from older swine) were examined by the HI test. Antibody was detected in 578 (72%) of 803 serums from older swine but not from any of the 438 serums from neonatal pigs. The 803 serums from older swine all were examined by the agar gel diffusion (AGD) test, and antibody was detected in 364 (45.3%). Some of the 803 serums (349 from butcher swine in Iowa) were also examined by the serum-neutralization (SN) test. The number and percentage of the 349 serums with detectable antibody by SN, HI and AGD tests were 331 (94.8%), 313 (89.7%) and 181 (51.9%), respectively.