Campylobacter is a leading cause of human gastroenteritis, with poultry serving as the primary reservoir host. Effective preharvest control strategies are crucial for preventing or reducing Campylobacter contamination on meat surfaces. As concerns grow regarding the use of antimicrobials in animal agriculture, the importance of non-antimicrobial preharvest strategies in poultry production has become increasingly significant. This comprehensive review focuses on the biology of Campylobacter, its impact on public health, and current and emerging preharvest strategies, with a special emphasis on vaccination. Preharvest strategies are broadly classified into biosecurity measures, gut microbiota modifications using prebiotics, probiotics, postbiotics, feed additives, and vaccination. While some vaccines have proven to be effective in research settings, no commercial vaccines are currently available. Because no single strategy can effectively combat Campylobacter, integrating multiple approaches, such as improved biosecurity measures, immunization, and dietary modifications, may provide a solution for reducing Campylobacter loads in poultry. Embracing a “One Health” approach, gaining a deeper understanding of Campylobacter pathophysiology, advancing vaccine technology, and implementing holistic farm management practices will be essential for the sustainable control of Campylobacter and for reducing the risk of human campylobacteriosis.

Campylobacter hepaticus is known to cause spotty liver disease (SLD) in layer chickens around peak production. Here, we report the complete genome sequences of two C. hepaticus strains, USA1 and USA5, from the United States. The genomes comprise chromosomes of 1,508,744 and 1,531,174 bp, respectively, with a G + C content of 28%.

Campylobacter is a leading cause of human gastroenteritis, with poultry serving as the primary reservoir host. Effective preharvest control strategies are crucial for preventing or reducing Campylobacter contamination on meat surfaces. As concerns grow regarding the use of antimicrobials in animal agriculture, the importance of non-antimicrobial preharvest strategies in poultry production has become increasingly significant. This comprehensive review focuses on the biology of Campylobacter, its impact on public health, and current and emerging preharvest strategies with a special emphasis on vaccination. Preharvest strategies are broadly classified into biosecurity measures, gut microbiota modifications using prebiotics, probiotics, postbiotics, feed additives, and vaccination. While many live, attenuated, and subunit vaccines have proven effective in research settings, there are currently no commercial vaccines available. Because no single strategy can effectively combat Campylobacter, integrating multiple approaches, such as improved biosecurity measures, immunization, and dietary modifications, may provide a solution for reducing Campylobacter loads in poultry. Embracing a “One Health” approach, gaining a deeper understanding of Campylobacter pathophysiology, making advancements in vaccine technology, and implementing holistic farm management practices will be essential for sustainable control of Campylobacter and for reducing the risk of human campylobacteriosis.

Background: Non-typhoidal Salmonella (NTS) is a major foodborne pathogen, with poultry products, especially eggs, being the primary source of human infections. Current serovar-specific poultry vaccines effectively reduce targeted Salmonella serovars but may inadvertently promote the emergence of untargeted serovars within poultry flocks. Therefore, novel vaccine candidates providing broad cross-serovar protection are needed to improve overall effectiveness of Salmonella control programs. Objectives: This study evaluated the immunogenicity of the novel subunit vaccine candidate InvG and assessed its ability to reduce Salmonella colonization in vaccinated laying hens and their progeny through maternally derived antibodies transferred via egg yolk. Methodology: Three experiments were performed. Experiment I evaluated the immunogenicity of purified recombinant InvG by (a) measuring anti-InvG antibodies using an enzyme-linked immunosorbent assay (ELISA) and (b) completing transcriptomic profiling of immune responses in vaccinated chickens. Vaccinated chickens were subsequently challenged with Salmonella Enteritidis to assess the efficacy of anti InvG antibodies in reducing intestinal colonization of Salmonella. Experiment II involved immunizing hens with InvG, to evaluate passive transfer of antibodies via egg yolk and the protective efficacy of maternally derived antibodies against Salmonella challenge. Passive transfer was assessed by measuring IgY antibodies in hen serum, egg yolk, and progeny serum, as well as secretory IgA (sIgA) antibodies in progeny intestinal washings using ELISA. Protective efficacy was evaluated by orally challenging one-day-old chicks with three different Salmonella serovars. Experiment III assessed the persistence of anti-InvG antibodies in the serum of vaccinated hens and their transfer into eggs following two doses of InvG. Results: InvG vaccination induced robust IgY antibody responses in hens, with efficient maternal antibody transfer to progeny via egg yolk. A statistically significant reduction in Salmonella colonization was observed in both vaccinated hens and their progeny. Conclusions: These findings demonstrate that InvG represents a promising subunit vaccine candidate for Salmonella control in poultry and warrants further investigation towards development as a broadly protective commercial poultry vaccine against Salmonella.

Campylobacter hepaticus is the etiological agent of Spotty Liver Disease (SLD), a newly emerging bacterial disease of laying hens resulting in significant mortality and production losses primarily in free-range systems. Although its economic impact continues to grow, the molecular basis of C. hepaticus pathogenesis remains poorly understood. In this study, we conducted transcriptomic profiling of C. hepaticus in three host-relevant conditions, exposure to chicken bile, infection of a chicken liver hepatocellular carcinoma (LMH) cell line, and isolation from liver lesions of naturally infected chickens. Through RNA-seq analysis, we found unique gene expression signatures in each environment. In the bile, C. hepaticus exhibited differential expression of 412 genes, with upregulation of genes related to motility, cell envelope remodeling, glycosylation, nitrate respiration, and multidrug efflux systems, indicating a stress-adaptive, metabolically active lifestyle. In LMH, on the other hand, 125 genes were differentially expressed, primarily reflecting downregulation of motility, oxidative stress response, chaperones, and core metabolic processes, suggesting that these cells adopt a less active, intracellular dormant lifestyle. Transcriptomic analysis of C. hepaticus isolated from the liver identified 26 differentially expressed genes, featuring selective upregulation of genes associated with nitrate respiration, sulfur metabolism, and pyridoxal 5’ phosphate homeostasis, alongside downregulation of the major outer membrane porin (momp), stress response chaperones (dnaK, groL), and genes involved in oxidative stress defense and energy production. Furthermore, the immune evasion-related gene cmeA and a glycosyltransferase gene were found to be highly upregulated. This study presents the first in-depth transcriptomic exploration of C. hepaticus in multiple host relevant niches. Our findings reveal niche-specific gene expression profiles and highlight metabolic and structural adaptations that enable C. hepaticus to survive during bile exposure, persist within host cells, and contribute to liver pathology. These insights provide a basis for identifying novel virulence determinants and may inform the development of targeted interventions, including vaccines or antimicrobial therapy, to control SLD in commercial poultry operations.

Campylobacter hepaticus is the etiologic agent of Spotty Liver Disease (SLD), a newly emerging bacterial disease of laying hens resulting in massive mortality and production losses primarily in free-range systems. Although its economic impact continues to grow, the molecular basis of C. hepaticus pathogenesis is poorly understood. In this study, we conducted transcriptomic profiling of C. hepaticus in three host-relevant conditions, exposure to chicken bile, infection of a chicken liver hepatocellular carcinoma (LMH) cell line, and isolation from liver lesions of naturally infected chickens. Through RNA-seq analysis, we found unique gene expression signatures in each environment. In bile, C. hepaticus exhibited differential expression of 412 genes, with upregulation of genes related to motility, cell envelope remodeling, glycosylation, nitrate respiration, and multidrug efflux systems, indicating a stress-adaptive, metabolically active lifestyle. In LMH cells, on the other hand, 125 genes were differentially expressed, primarily reflecting downregulation of motility, oxidative stress response, chaperones, and core metabolic processes, which suggests of a low-activity, intracellular dormant lifestyle. Transcriptomic analysis of C. hepaticus isolated from the liver identified 26 differentially expressed genes, featuring selective upregulation of nitrate respiration, sulfur metabolism, and pyridoxal 5’ phosphate (PLP) homeostasis, along with down regulation the major outer membrane porin (mompA), stress response chaperones (dnaK, groL), and genes involved in oxidative stress defense and energy production-. Further, immune evasion-related gene cmeA and a glycosyltransferase were found to be highly upregulated. This work presents the first in-depth transcriptomic exploration of C. hepaticus in multiple host relevant niches. Our findings reveal niche-specific gene expression profiles and highlight metabolic and structural accommodations allowing C. hepaticus survival during bile exposure, persistence within host cells, and induction of liver pathology. These insights provide a basis for the identification of novel virulence determinants and may inform the development of targeted interventions, including vaccines or antimicrobial therapy, to control SLD in commercial poultry operations.