Where does the infectious coryza bacterium (Avibacterium paragallinarum) localize to cause classical facial swelling in brown layers?

Infectious Coryza is a severe respiratory disease caused by the bacterium *Avibacterium paragallinarum*. The primary site of localization and pathological damage is the nasal cavity and the paired infraorbital sinuses, located just below and in front of the eyes. Once the bacterium colonizes these membranes, it triggers acute catarrhal inflammation. This leads to the hypersecretion of thick, foul-smelling nasal exudate that cannot drain properly, causing the infraorbital sinuses to swell dramatically. This swelling presents as the classical "owl head" facial edema, accompanied by conjunctivitis and closed eyelids. This localized inflammation causes severe pain, preventing the birds from eating and drinking, which leads to immediate drops in egg yield. Farmers can study respiratory bacteriology in the Poultry Encyclopedia, buy broad-spectrum antibiotics and sinus flush treatments on Poultry Plaza, track daily market rates on Poultry Rates, and trade recovered flocks on Murghi Mandi.