Infectious coryza outbreak in a table egg layer flock in Alberta.

Infectious coryza (IC) is an economically important, acute, and highly contagious respiratory disease of chickens caused by <i>Avibacterium paragallinarum</i>. A case of 27-week-old table egg layers was submitted to the Diagnostic Services Unit, Faculty of Veterinary Medicine, University of Calgary (Alberta). The chickens had a history of swollen faces, eyelids, combs, and wattles; lacrimation; and nasal discharge with increased mortality and an acute drop in egg production of up to 14%. <i>Avibacterium paragallinarum</i> was cultured from infraorbital sinuses and wattle samples. Whole-genome sequencing based multilocus sequence typing identified <i>A. paragallinarum</i> sequence type-8, and genomic analysis of <i>HMTp210</i> gene predicted Page serovar C. In the same time frame, IC outbreaks were also recorded in 3 other flocks in Alberta and some flocks in Saskatchewan and Manitoba. In addition to IC, infectious bronchitis virus was identified. The disease was linked to the introduction of subclinically infected pullets from another province into this flock of naïve birds. This is the first reported case of IC in recent times in Alberta. Screening birds for infectious disease status should be a critical practice if a carrier state exists in long-lived birds. Key clinical message: This outbreak underscores the need for strict biosecurity. Avoid introducing new birds to closed flocks. If necessary, rule out infections with carrier states through appropriate screening.