Safety and efficacy of anaroA-deleted live vaccine against avian colibacillosis in a multicentre field trial in broilers in Morocco

Abstract

The safety and efficacy of an aroA-deleted live vaccine against avian colibacillosis (Poulvac(®) E. coli) was evaluated in broilers in a multicentre field trial. The trial sites consisted of 18 paired bird houses (randomly assigned to either the vaccination or the control treatment groups) located in 15 farms in three different regions of Morocco. A field dose of vaccine was administered on day of hatch by the spray route. Both clinical and performance parameters were compared between vaccinated and control groups, in which the experimental unit was defined as the individual bird house. No adverse reactions attributable to the vaccine were observed throughout the study. Non-inferiority of the vaccinated bird houses versus the control houses during a 2-week period post vaccination was statistically demonstrated for mortality and average daily weight gain. Vaccine efficacy was confirmed based on significant differences between vaccinated and unvaccinated groups measured for the full duration of the trial, including colibacillosis-like lesions observed at slaughter (1.7 versus 3.5%; P = 0.0054), total mortality (9.3 versus 10.3%; P = 0.0203), average daily weight gain (47.8 versus 46.2 g/day; P = 0.0006), average number of antibiotic treatment days (0.5 versus 2.0; P = 0.0008) and percentage of the birds that was marketed (90.0 versus 89.0%; P = 0.0309). In conclusion, the vaccine was demonstrated to be both safe and efficacious under field conditions.

Immune responses associated with homologous protection conferred by commercial vaccines for control of avian pathogenic Escherichia coli in turkeys

“…No booster was given to those birds at 7 days of age via drinking water as is recommended [ 22 ]. A recent field trial of Poulvac® E. coli [ 42 ] also supports that giving a booster in drinking water is not necessary. Interestingly, a higher level of peripheral B lymphocytes was detected in the control than the vaccinated group and the authors speculated that Poulvac® E. coli may suppress humoral responses and that they may therefore be dispensable in protection [ 43 ].…”

“…However, cytokine responses to APEC vaccination have not previously been analysed. Similarly, whilst live-attenuated mutants of various kinds can confer resistance against APEC in target host species [ 21 , 22 , 30 , 42 - 44 ], the innate and cell-mediated responses they elicit are ill-defined. Studies by Fernandez Filho et al [ 43 ] with Poulvac® E. coli only examined peripheral cellular responses to vaccination, with a fine spray, of day-old chicks.…”

An Assessment of the Level of Protection Against Colibacillosis Conferred by Several Autogenous and/or Commercial Vaccination Programs in Conventional Pullets upon Experimental Challenge

“…The immunization of pullets/hens against colibacillosis with live, inactivated or sub-unit vaccines has been reported, with variable outcomes [ 6 ]. Live vaccines have been repeatedly proven to contribute positively to bird protection [ 26 , 27 , 28 , 29 , 30 ], although exceptions have also been reported [ 31 ]. A commercial live vaccine is presently available in most regions; it was registered in the EU in 2013 [ 32 ] and it is an attenuated O78 E. coli strain and provides effective protection upon challenge with O78 wild strains [ 33 ].…”

Efficacy of an avian colibacillosis live vaccine for layer breeder in Japan

“…papA , papG , iutA and clpG [ 2 , 11 ], deletion of ibeA or pst genes, have all succeeded in reducing virulence [ 7 , 22 ]. Furthermore, there are many reports of the efficacy of the ΔaroA vaccine and its potential is widely recognized [ 4 , 5 , 10 , 13 , 17 ]. However, deletion of only the aroA gene is not enough to attenuate the full pathogenicity and deletion of an additional gene such as the luxS gene is required [ 6 , 18 ].…”