Vaccination with an <i>Escherichia coli</i> F4/F18 Vaccine Improves Piglet Performance Combined with a Reduction in Antimicrobial Use and Secondary Infections Due to <i>Streptococcus suis</i>

Post-weaning diarrhea (PWD) due to <i>Escherichia coli</i> (<i>E. coli</i>) remains a major cause of economic losses for the pig industry. Therapy to combat PWD typically consists of antibiotic treatment or supplementation of zinc oxide to the feed. The emergence of antimicrobial resistance to <i>E. coli</i> and new EU regulations prompt the need for alternative control strategies, such as immunization. The aim of the field study was to evaluate the effect of an oral live non-pathogenic <i>E. coli</i> vaccine on piglet performance, health, and antimicrobial use. We evaluated vaccination with an oral live non-pathogenic <i>E. coli</i> F4/F18 under field conditions in 10 consecutive batches against a standard antimicrobial treatment in 10 historical control batches. The vaccine-treated groups demonstrated a significant improvement in feed conversion rate, mortality weight, and antimicrobial use. From a general health perspective, secondary infections due to <i>Streptococcus suis</i> (<i>S. suis</i>) in the second part of nursery were markedly reduced, as indicated by the reduction in amoxicillin use. In conclusion, the present study demonstrates the efficacy of an oral live non-pathogenic <i>E. coli</i> vaccine for active immunization of piglets against PWD under field conditions. The vaccine-treated groups showed an improvement in several economically important performance parameters while reducing the overall antimicrobial use and infection pressure due to <i>S. suis</i>. Therefore, vaccination against PWD may be considered a valuable alternative for consolidating piglet performance while meeting the new EU requirements concerning the prudent use of antimicrobials in intensive pig production.