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Infectious coryza

VLA has confirmed two separate cases of infections coryza in hobby flocks in southern England.

Veterinarians should therefore consider infectious coryza as a differential diagnosis of upper respiratory tract disease, especially in chickens.

We would be interested to hear of any suspected cases of infectious coryza. Please contact your local VLA regional laboratory to discuss with a Veterinary Investigation Officer (VIO).

Background

Infectious coryza (IC) is a well-characterised bacterial respiratory disease of poultry (mainly chickens) caused by Avibacterium paragallinarum, formerly known as Haemophilus paragallinarum. IC is not known to be zoonotic and therefore, there is no known risk to public health.

The disease is of economic importance to the poultry industry in many parts of the world such as Asia, the Americas and parts of Africa. It is also present in continental Europe.

Clinical signs

The disease is characterised in chickens by acute respiratory signs, often with swelling of the infra-orbital sinuses and/or face, and nasal discharge (Figure 1). There is usually high morbidity and low mortality.

Other clinical presentations may be seen when infection is complicated by the presence of other viral or bacterial pathogens or other factors such as husbandry conditions, which can alter the clinical presentation and affect severity, and complicate the diagnosis.

The effects of the disease are also known to be more severe in multiple-age flocks when younger, non-immune birds come into contact with recovered older birds.

There may also be losses in production including reduced growth in broilers and a drop in egg production in layers.

Disease control

In the short term, IC has been controlled by antibiotic medication in the affected flocks in Great Britain. At present authorisation from the Veterinary Medicines Directorate is required for the importation of any infectious coryza vaccines.

VLA investigation

Following scanning surveillance investigations by VLA regional laboratories, IC has been confirmed by bacteriological and PCR testing in two separate hobby flocks in southern England (Welchman and others, 2010).

Infection is likely to have been introduced to the flocks via the purchase of infected chickens carrying the organism. The original source of infection is unknown.