Abstract
The prevention of avian colibacillosis has historically been investigated through vaccination, with variable outcomes. Commercial live (attenuated) and inactivated vaccines are reported to have limited efficacy in the context of heterologous challenge. Autogenous vaccination, using field isolates, is widely used, but scarcely documented. Different vaccination programs, including a live commercial vaccine and/or an inactivated autogenous vaccine, were compared for three different avian pathogenic Escherichia coli (APEC) strain (serotypes O78, O18 and O111) challenges. On the pullet farm, four groups of conventional pullets received different vaccination protocols. Group A was kept unvaccinated (control group). Group B was vaccinated three times with a live commercial O78 E. coli vaccine (at one day old, 59 and 110 days of age). Group C was immunized twice (at 79 and 110 days) with a three-valence autogenous vaccine (O78, O18 and O111). Group D was vaccinated first with the commercial vaccine (at one day old and 59 days), then with the autogenous vaccine (110 days). Birds were transferred to the experimental facility at 121 days of age and were challenged 10 days later. In each group, 20 birds were challenged with one of the three APEC strains (O78, O18, O111); in total, 80 birds were challenged by the same strains (20 per group). The recorded outcomes were: mortality rate, macroscopic lesion score in target organs and the bacterial recovery of the challenge strain from bone marrow and pooled organs. When challenged with O78 or O111 strains, birds from groups C and D proved to be significantly better protected, in terms of lesion scoring and bacteriological isolation, than those of groups A and B. With the O18 challenge, only birds of group D presented a statistically significant reduction of their lesion score. To the authors’ knowledge, this is the first report on the efficacy of an immunization program in poultry that combines commercial and autogenous vaccines.
Highlights
Escherichia coli is a Gram-negative bacterium that typically inhabits the intestine of vertebrates and is considered a usual member of the digestive flora in animals
20 birds were challenged with one of the three avian pathogenic E. coli (APEC) strains (O78, O18, O111); in total, 80 birds were challenged by the same strains (20 per group)
Colisepticemia/polyserositis, peritonitis/oviduct infection/oophoritis, swollen head syndrome and colibacillosis of the lower respiratory system have been described in adult birds, while omphalitis is observed in day-old chicks
Summary
Escherichia coli is a Gram-negative bacterium that typically inhabits the intestine of vertebrates and is considered a usual member of the digestive flora in animals. E. coli strain escapes digestive barriers and invades the internal organs It is reported as the most common infectious disease in poultry and is prevalent in laying production; its economic impact is substantial in the poultry industry [1,2] and potentially in public health [3]. Colisepticemia/polyserositis, peritonitis/oviduct infection/oophoritis, swollen head syndrome and colibacillosis of the lower respiratory system have been described in adult birds, while omphalitis is observed in day-old chicks. The ability of such E. coli strains to cause localized and systemic disease is termed avian pathogenic E. coli (APEC). The serotypes most frequently reported to cause colibacillosis in poultry are O1, O2 and O78 [7,8], while many other serotypes have been sporadically incriminated, such as O111 in layer chickens with colibacillosis and peritonitis [9,10]
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