Gallibacterium anatis in Laying Hens: Pathology, gtxA Toxin & AMR
A veterinary reference guide to Gallibacterium anatis biovar haemolytica, salpingitis-peritonitis complex, RTX toxins, and multidrug resistance.
Scientific Overview
Gallibacterium anatis (formerly Pasteurella haemolytica) has emerged globally as a primary bacterial pathogen of mature laying hens, broiler breeders, and geese. Characterized by high multidrug resistance (MDR) exceeding 20% to 30% across European, Asian, and North American commercial isolates, G. anatis causes severe salpingitis, peritonitis, egg drops, and respiratory airsacculitis.
Pathogen Overview & Virulence Determinants (gtxA RTX Toxin)
Gallibacterium anatis is defined as a Gram-negative, facultatively anaerobic bacterium of the family Pasteurellaceae. The pathogenic strain Gallibacterium anatis biovar haemolytica expresses a potent hemolytic leukotoxin, GtxA (RTX toxin), present in 100% of virulent clinical isolates (Algammal et al., 2022; Karwańska et al., 2023).
The GtxA RTX toxin destroys avian leukocytes and epithelial cells in the oviduct. Adherence is facilitated by FlfA fimbriae and biofilm-forming capsules, allowing the pathogen to persist in mucosal linings and evade host immune responses (Guo et al., 2025; Nofouzi et al., 2025).
Gross Pathological Lesions & Clinical Signs
Necropsy findings in laying flocks affected by G. anatis:
- Salpingitis & Peritonitis: Massive accumulation of foul, yellow, caseous (cheesy) exudate distending the oviduct magnum and uterine lumen. Fibrinous coelomitis coating abdominal organs.
- Oophoritis & Ovarian Regression: Misshapen, hemorrhagic, or liquefied ovarian follicles undergoing rapid atrophy.
- Respiratory Signs: Tracheal rales, facial edema, and airsacculitis, frequently co-infecting alongside APEC E. coli or Infectious Bronchitis Virus (El-Ghany et al., 2023).
- Production Impact: Sudden 10% to 30% drop in Hen-Day egg production with elevated flock mortality (2% to 15%). Track flock lay rates in our Hen-Day Production Calculator.
Antimicrobial Resistance (AMR) & Antimicrobial Stewardship
Recent microbiological surveillance confirms that G. anatis isolates display extensive drug resistance (XDR) and multidrug resistance (MDR) against beta-lactams, tetracyclines, sulfonamides, and fluoroquinolones (Algammal et al., 2022; Kursa et al., 2023; Karwańska et al., 2023).
Treatment & Control: Empirical antibiotic therapy without culture sensitivity testing frequently fails. Control relies on autogenous bacterin vaccines, strict biosecurity to prevent vertical transmission from breeder stocks, and water acidification to break horizontal transmission cycles.
All scientific data, diagnostic criteria, and performance benchmarks presented on this page are derived from published peer-reviewed journals and official veterinary codes:
- Avian Pathology & Diagnostics: World Organisation for Animal Health (WOAH, 2023). Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. Paris, France.
- Poultry Diseases & Histology: Swayne, D.E., et al. (2020). Diseases of Poultry (14th ed.). Wiley-Blackwell / American Association of Avian Pathologists.
- Nutrition & Feed Chemistry: Leeson, S. & Summers, J.D. (2001). Commercial Poultry Nutrition (3rd ed.). University Books, Guelph, Ontario.
- Commercial Breed Standards: Aviagen (2024). Ross 308 & Cobb 500 Broiler Performance Objectives. / Lohmann Breeders (2024). Lohmann Brown Management Guide.