EXPERIENCE WITH A PLANNED EXPOSURE PROGRAM FOR THE CONTROL OF ENZOOTIC TRANSMISSIBLE GASTROENTERITIS IN SWINE

Oral inoculation of pregnant sows and gilts with a homogenate of pig i ntestines containing live, virulent transmissible gastroenteritis (TGE ) virus was associated with significant (P < 0.01) reduction of mortal ity in nursery pigs in a herd affected with enzootic TGE. The mortalit y of weaned pigs from April through June 1981, when sows were not vacc inated or inoculated, was 9.3%. Mortality of weanling pigs from July t hrough December 1981 was 5.7% (P < 0.01), and staved consistently betw een 2.6 and 4.8% from 1982 through 1990. After beginning the exposure program, there were no clinical signs attributable to TGE in the farro wing house or nursery until 1986, when recrudescence of TGE was eviden t in the nursery. Although the source of the virus could not be substa ntiated. recrudescence suggested that TGE virus would not be eradicate d as long as exposure was continued. The most plausible explanation fo r the decrease in the incidence of diarrhea and mortality in the nurse ry pigs after initiation of the planned exposure program is that a hig her, longer lasting amount of lactogenic immunity was provided to suck ling pigs. Presumably over time, this resulted in less TGE virus carry -over into the nursery by weanling pigs, thereby reducing and confinin g the environmental challenge to the nursery. Strict all-in, all-out p ig movement in the nursery with thorough cleaning and disinfecting pre sumably further reduced the environmental challenge.