COMBINED PARENTERAL AND ORAL IMMUNIZATION AGAINST DIARRHEA IN WEANED PIGLETS CAUSED BY ENTEROTOXIGENIC STRAINS OF ESCHERICHIA-COLI

Experiments were focused on diarrhea prevention in weaned piglets caus ed by enterotoxigenic strains of Escherichia coli (ETEC) with colonizi ng factor 8813. An immunization procedure consisted of intramuscular a pplication of ETEC strain bacterin a day before weaning and of peroral administration of a live culture of nontoxic E. coli strain with the same colonizing factor on the day of weaning. In an experiment on the litter of 10 piglets (six were immunized, four were controls), their i ntestines were colonized by the nontoxic E. coli strain for 4-7 days ( Fig. 1). The challenge peroral infection by virulent ETEC strain demon strated the protection of immunized piglets from the disease as well a s from intestinal colonization by the administered ETEC strain. The sa me immunization procedure was tested on three pig farms with enzootic occurrence of diarrheas in weaned piglets. On these farms, besides ETE C strain with colonizing factor 8813 (F18) ETEC strains with other col onizing factors (K88, F not specified) were found out in the weanlings - Tab. I. Immunization effect was evaluated according to the rate of mortality of immunized and nonimmunized piglets within a fortnight aft er weaning. Out of 222 immunized piglets on S farm (Tab. II), 25 pigle ts died (11.3%), out of 232 nonimmunized animals it was 39 that died ( 16.8%). As for T farm (Tab. III), 22 piglets (8.6%) died out of 255 im munized animals while 71 out of control 274 piglets died (25.7%). A to tal of 3,692 were immunized on V farm (Tab. IV). Ninety-four animals d ied among them (2.5%). Mortality rate in the control group of 6,301 an imals was 523 piglets (8.3%).