Efficacy and safety of Poulvac E. coli vaccine in broiler chickens challenged with E. coli serotype O78 and an acute field isolate

To evaluate efficacy concepts of Poulvac® E. coli live vaccine, five groups of day-old broilers were provided. Two groups were vaccinated, but challenged by different bacteria, one by E. coli O78 and the other with an untypable acute field E. coli isolate; the other two groups acted as positive control, not vaccinated, but challenged with the E. coli O78 and an untypable acute field isolate. The last group served as environmental control (not vaccinated, not challenged). The challenge was done intratracheally at day 28 and birds were necropsied and examined 1 week later to evaluate vaccine protection. A field trial was performed in 23,000-broiler farm containing two separate partitions with the same condition; one partition received the vaccine at 1-day age, but the other remained unvaccinated; both groups observed daily for 47 days to evaluate vaccine affection on growth, weight, and behavior. No unfavorable reaction, abnormal behavior, death, or gross lesion observed following administration of Poulvac® E. coli, Zoetis vaccine in vaccinated birds neither in efficacy survey, nor in field trial. Weighing data analysis before challenge implied that, in spite of a greater weighing number in vaccinated birds, there was no any significant difference between vaccinated and unvaccinated birds (P > 0.05). Following the challenge, vaccinated birds demonstrated milder signs; also, healthy carcasses increased in vaccinated birds (P = 0.000), which revealed that the vaccine can protect against both E. coli O78 and an acute field E. coli isolate. Altogether, factors which vaccine could cause significant difference were as follows: point prevalence, airsacculitis, pneumonia, peritonitis, final weight after challenge, and feed conversion ratio.