Infection Dynamics and Host Biomarker Identification for Spotty Liver Disease in Chickens

Area of Science:

• Veterinary Pathology
• Avian Health
• Molecular Epidemiology

Background:

• Spotty liver disease (SLD) significantly impacts commercial layer hens, causing liver lesions, reduced egg production, and increased mortality.
• The primary causative agent is *Campylobacter hepaticus*, leading to substantial economic losses in the poultry industry.

Purpose of the Study:

• To investigate the relationship between *Campylobacter hepaticus* infection, liver dysfunction, and reproductive impacts in layer hens.
• To identify host genetic markers for tracking SLD progression and potential therapeutic targets.

Main Methods:

• Oral inoculation of layer hens with *C. hepaticus* strain NSW44L.
• Quantification of pathogen colonization using qPCR in various tissues (liver, bile, caeca, spleen, ovarian follicles).
• Assessment of liver lesions and analysis of hepatic gene expression using RNA-sequencing (RNA-seq).

Main Results:

• Bacterial presence was detected in multiple organs, with peak loads in bile from day 6-7 post-inoculation.
• Liver lesions appeared from day 4 and peaked by day 6-7.
• Downregulation of yolk-precursor and metabolic genes (e.g., PRLR, DHCR7, ME1) and upregulation of avidin (AVD) and versican (VCAN) were observed.

Conclusions:

• Host gene expression changes, including AVD and VCAN upregulation, correlate with SLD progression.
• These molecular changes serve as potential biomarkers for effective SLD monitoring.
• Findings suggest avenues for developing targeted therapies against *Campylobacter hepaticus* infection in poultry.