It occurs mostly in chickens and is caused by Avibacterium paragallinarum. In general, the first sign is rhinitis with seromucinous discharges, often dries around the nasal orifices (Image 1).
Image 1 Seromucinous discharges are dried around the nasal orifices
Facial oedema in the infraorbital sinus area (Image 2). Usually, the state is accompanied by reduced food and water consumption, and in laying birds - with variable reduction in egg production.
Image 2 Facial oedema in the infraorbital sinus area
Oedema of wattles could be also observed, especially in males (Image 3). The involvement of the lower respiratory tract is rare.
Image 3 Oedematose wattle
After the attenuation of the inflammation, the affected wattles could remain wrinkled as a result of organization of the deposited exudate (Image 4).
Image 4 Wattle get wrinkles
IC should be differentiated from fowl cholera and hypovitaminosis A, which are with similar clinical signs.
(Source: "Diseases of poultry - A colour atlas" - Ivan Dinev & CEVA Santé Animal, 2010)