Cross-protection conferred by a live-attenuated Salmonella enteritidis vaccine against challenge with Salmonella Heidelberg and Salmonella infantis

Published: October 5, 2026

Source : Pablo Chacana 1, Lucas Sara 2, Facundo Ferrari 2, Luiz Sesti 3, Jaime Sarabia 4, Pascal Paulet 5, Patricia Joaquim 1, Facundo Balbiani 1, María Laura Socas 1, David Arenas 1 / 1 Instituto Nacional de Tecnología Agropecuaria, Argentina; 2 Ceva Salud Animal Argentina; 3 Ceva Salud Animal Latinoamérica; 4 Ceva Salud Animal España; 5 Ceva Salud Animal Francia.

Salmonella infections cause enteric diseases in humans and animals, and poultry production is generally associated with contamination by this foodborne pathogen. S. enteritidis (SE) and S. typhimurium (ST), as well as other serotypes such as S. Heidelberg (SH) and S. infantis (SI), are highly prevalent. This study evaluated the protection conferred by a live SE vaccine (auxotrophic for the amino acids adenine and histidine) in laying hens exposed to field strains of SH or SI.

One-day-old chicks were randomly divided into vaccinated and unvaccinated groups. Birds in the vaccinated group (n=50) were immunized with Cevac® Salmovac on day 1, week 6, and week 13 via the oral route, while birds in the unvaccinated group (n=50) did not receive the vaccine. In week 16, the birds in each group were divided into two subgroups and exposed to an infectious dose of SH (10^8 CFU/bird) or SI (10^9 CFU/bird).

At 3, 5, 10, and 14 days post-challenge (dpd), pathogen excretion was determined using individual cloacal swabs; the samples were enriched in tetrathionate broth, and the strain was then detected on XLD agar plates. In addition, at 5 and 14 dpd, five birds from each group were euthanized, and a Salmonella count was performed on the cecal contents.

SH excretion was significantly reduced in birds from the vaccinated group at 3 (P=0.0001) and 5 (P< 0.0001) dpd compared with unvaccinated birds. The SH strain could not be detected in the cecal samples from vaccinated birds analyzed on both sampling days. In contrast, SH was recovered from all unvaccinated birds sampled at 5 dpd and from 2 out of 5 birds at 14 dpd.

A similar significant reduction in excretion was observed in vaccinated birds exposed to IS. IS excretion was significantly reduced in birds from the vaccinated group at 3 (P=0.0031), 5 (P=0.0001), and 10 (P=0.0079) dpd. SI could not be detected in vaccinated birds, but it was recovered from 4 out of 5 unvaccinated birds sampled at 5 dpd and from 1 out of 5 birds at 14 dpd.

These results demonstrate that Cevac® Salmovac was able to significantly reduce the replication of the SH and SI challenge strains in vaccinated birds.

Keywords: Salmonella, Cross-protection, Live attenuated vaccine.

Abstract published in Veterinaria (Montevideo), 61(Suplemento 1), 35. https://www.revistasmvu.com.uy/index.php/smvu/article/view/1431.