Development of an IgY-Based Vaccine for Salmonella Control in Poultry

Background: Salmonella infections in poultry pose significant public health and economic challenges due to contamination of meat and eggs and the rise of antimicrobial resistance. Innovative control strategies are needed to reduce Salmonella in poultry flocks. Methods: We explored a novel approach integrating a live attenuated Salmonella vaccine and IgY antibody therapy. Several indigenous plant extracts were screened as natural attenuating agents for Salmonella. The most effective (garlic and onion extracts) were used to attenuate a cocktail of five wild-type Salmonella serovars (S. Montevideo, S. Yeerongpilly, S. Augustenborg, S. Kentucky, and S. Typhimurium). Chickens were immunized with the plant-attenuated Salmonella vaccine, and the resulting egg yolk IgY antibodies were harvested. We assessed in vitro bacterial growth inhibition, vaccine safety and immunogenicity (via ELISA for anti-Salmonella IgY), and performed statistical analyses to evaluate significance. Results: Garlic and onion extracts markedly inhibited Salmonella growth in vitro, yielding significantly smaller colonies (1.0–1.5 mm) compared to untreated controls (4.1 mm, p < 0.05). Combining garlic and onion achieved complete inhibition (no visible colonies), indicating a potent attenuation effect. Plant-extract attenuation did not compromise immunogenicity: chickens vaccinated with the attenuated strains developed high titers of anti-Salmonella IgY, with ELISA optical density values (~1.2 at 1:500 dilution) far above the negative cut-off (0.35). The IgY antibodies showed strong agglutination of Salmonella and are expected to confer passive protection. Recent studies corroborate that orally administered anti-Salmonella IgY can reduce intestinal colonization and shedding in chickens. Conclusion: This study demonstrates a feasible, cost-effective strategy for Salmonella control in poultry by using indigenous plant extracts to create a live attenuated vaccine and harnessing resultant IgY antibodies for therapy.