# Safety, Immunogenicity, and Vaccine Compatibility of a Trivalent Inactivated In Ovo Nanovaccine Against Avian Colibacillosis in Broilers Under Commercial Hatchery Conditions

## TL;DR

A new in ovo nanovaccine against avian colibacillosis was found to be safe and effective in broilers under commercial conditions.

## Contribution

The study introduces a novel in ovo nanovaccine using inactivated E. coli strains and cationic maltodextrin nanoparticles for avian colibacillosis.

## Key findings

- The vaccine did not affect hatchability, survival, or growth performance in broilers.
- Vaccinated birds developed a measurable antibody response against E. coli that lasted until slaughter age.
- The vaccine was compatible with other in ovo live-attenuated viral vaccines without interfering with their effectiveness.

## Abstract

Avian colibacillosis is a major cause of economic losses in poultry production worldwide. Control of the disease is increasingly challenging due to rising antibiotic resistance, highlighting the need for effective vaccination strategies suitable for large-scale use. In this study, we evaluated an in ovo nanovaccine candidate against avian colibacillosis in broilers based on three inactivated Escherichia coli strains that are associated with cationic maltodextrin nanoparticles. The vaccine was assessed under commercial conditions in a Brazilian broiler hatchery. In ovo administration of the vaccine was well tolerated and did not negatively affect hatchability, survival, growth performance, or feed efficiency. Vaccinated birds developed a measurable antibody response against E. coli from 14 days post-hatch, which persisted until slaughter age. Importantly, the vaccine did not interfere with the immune response to other routinely used in ovo live-attenuated viral vaccines. These results support the potential of this inactivated nanovaccine as a safe and practical preventive approach against avian colibacillosis in commercial broiler production systems.

Avian colibacillosis, caused by Escherichia coli, remains a significant threat to poultry health and production, particularly in the context of rising antimicrobial resistance. Efficient and scalable vaccination strategies are needed to reduce economic losses and reliance on antibiotics. This study investigated the safety and immunogenicity of a novel single-dose in ovo vaccine candidate based on three inactivated E. coli strains formulated with cationic maltodextrin nanoparticles. The vaccine was evaluated in broilers under commercial hatchery conditions. In ovo administration was well tolerated and did not adversely affect hatchability, survival, growth performance, or feed efficiency. Vaccinated birds mounted a measurable serum immunoglobulin Y (IgY) response against E. coli from 14 days post-hatch, which persisted until slaughter age. Furthermore, when co-administered with routinely used live-attenuated viral vaccines, no interference with the immunogenicity of these vaccines was observed. These results demonstrate that the inactivated nanovaccine is safe, immunogenic, and compatible with an industrial-scale in ovo vaccination. The findings support its potential as a practical prophylactic approach to prevent avian colibacillosis in broiler production.