The Influence of Vaccination of Broiler Chickens and Turkeys with Live <i>E. coli</i> Attenuated Vaccine on <i>E. coli</i> Population Properties and TRT Vaccination Efficacy
Marcin Śmiałek | Joanna Kowalczyk | Andrzej Koncicki
Colibacillosis is one of the major causes of economic losses in the poultry industry. Vaccination against <i>E. coli</i> is attracting increasing interest. The aim of the study was to evaluate the influence of vaccination with live, <i>aroA</i> gene-deleted vaccine on the structure and properties of field <i>E. coli</i> population and its potential impact on TRT vaccination efficacy in broiler chickens and turkeys. We performed three independent experiments on farms: (1) with antibiotic-free broiler chickens, (2) with conventional broiler chickens and (3) with broiler turkeys. In experiment 1, we have recorded an approx. 0–15% prevalence of multi-susceptible <i>E. coli</i> strains in the first production cycle. Starting from production cycle number two, after vaccination introduction, successive significant increases in <i>E. coli</i> susceptibility emerged, reaching 100% of strains at the end of production cycle 3. Increased <i>E. coli</i> susceptibility remained for three production cycles after vaccination withdrawal. In experiments 2 (2 production cycles) and 3 (1 production cycle), we recorded similar tendencies of <i>E. coli</i> susceptibility profile change. In experiments 1 and 2, the <i>E. coli</i> population count was lower after vaccination. In experiments 2 and 3, no negative influence of <i>E. coli</i> vaccination on the level of specific antibodies against TRT was recorded.
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