EVALUATION OF COMBINED ANTIBIOTIC AND COMPETITIVE-EXCLUSION TREATMENTIN BROILER BREEDER FLOCKS INFECTED WITH SALMONELLA-ENTERICA SEROVAR ENTERITIDIS

Strategic medication in breeding flocks of domestic fowl (Gallus gallu s), using antimicrobial treatment followed by competitive exclusion, w as evaluated in 13 trials between February and September 1993. In each trial, the flock had been confirmed as naturally infected with Salmon ella enterica serovar Enteritidis and the effect of treatment was dete rmined on salmonella isolation from tissues. Of 11 trials where enrofl oxacin was used, a long-term reduction of salmonella was observed in t wo and a shea-term reduction was measured in birds from another five t rials. Salmonella Enteritidis was isolated from birds after treatment in four other trials with enrofloxacin and in two trials of medication with amoxycillin. After treatment with enrofloxacin significant reduc tions were found in the prevalence of S. Enteritidis in tissues from b irds, and in levels and prevalence of salmonellas in their environment . No salmonella was identified in statutory meconium samples taken fro m the hatched chicks derived from the flocks after treatment. The prog ramme of antibiotic treatment and competitive exclusion offers an alte rnative to slaughter, but the approach must be part of a co-ordinated programme which will effect a decrease in the prevalence of S. Enterit idis over time by contemporary use of disease security measures. The r isk of development of antimicrobial resistance is also discussed.