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Gallibacterium anatis bv. haemolytica (formerly Pasteurella haemolytica) occurs as a commensal of the upper respiratory tract and lower reproductive tract of healthy chickens, but has also been implicated as a cause of salpingitis and peritonitis in breeders and commercial table egg layers in multiple countries, resulting in decreased egg production and increased mortality.
Recent increases in isolation and reports of significant disease, mortality and economic loss associated with G. anatis infection suggest that this bacterium may be an emerging pathogen of poultry.
Introduction
Gallibacterium anatis, a member of the family Pasteurellaceae, has two distinct biovars; G. anatis bv. haemolytica and G. anatis bv. anatis (18).
The pathologically significant G. anatis bv. haemolytica, named for its ability to hemolyze red blood cells, was previously designated Pasteurella haemolytica. G. anatis is a cause of salpingitis and peritonitis in laying chickens, and has also been isolated as a cause of disease in ducks, geese and ostriches (1).
The Commensal to Pathogen Switch
Although increasingly identified as a cause of disease in chickens, particularly in laying hens (Fig. 1) (9), the pathogenic potential of G. anatis remains controversial. On the one hand, G. anatis may occur as a normal part of the microbiota of the upper respiratory tract and lower reproductive tract of chickens, without any adverse effects on health or productivity.
G. anatis has, however, been identified as a cause of septicemia, pericarditis, hepatitis, oophoritis, salpingitis, peritonitis and follicle degeneration, with subsequent significant negative effects on flock livability and productivity (18).
Factors contributing to the potential pathogenic action of G. anatis
While the switch from commensal to pathogen is not fully understood, several host- specific factors may contribute to the manifestation of G. anatis as an opportunistic pathogen; including:
Age
Hormonal influences,
Stress,
Seasonal changes,
Immune suppression
Genetic predisposition (possibly)
We most commonly isolate G. anatis from breeders and layers around peak egg production, although isolations have been made during all stages of production.
G. anatis is frequently isolated with E. coli, and it is plausible that coinfection with E. coli or other microorganisms may enhance the pathogenic effects of G. anatis. G. anatis may, howeve...
