Otitis and meningoencephalitis associated with infectious coryza ( Avibacterium paragallinarum) in commercial broiler chickens

Abstract

Infectious coryza, caused by Avibacterium paragallinarum, is an acute respiratory disease of poultry that can result in substantial morbidity, mortality, and economic losses. In March 2017, the Turlock branch of the California Animal Health and Food Safety laboratory system encountered an unusual clinical and pathologic presentation of infectious coryza in 6 live, 29-d-old, commercial broiler chickens that were submitted for diagnostic investigation. Antemortem evaluation revealed severe neurologic signs, including disorientation, torticollis, and opisthotonos. Swollen head-like syndrome and sinusitis were also present. Histologically, severe sinusitis, cranial osteomyelitis, otitis media and interna, and meningoencephalitis were noted, explaining the clinical signs described. A. paragallinarum was readily isolated from the upper and lower respiratory tract, brain, and cranial bones. Infectious bronchitis virus (IBV) was also detected by PCR, and IBV was isolated in embryonated chicken eggs. Based on sequencing analysis, the IBV appeared 99% homologous to strain CA1737. A synergistic effect between A. paragallinarum and IBV, resulting in exacerbation of clinical signs and increased mortality, may have occurred in this case. A. paragallinarum should be considered among the possible causes of neurologic signs in chickens. Appropriate media should be used for bacterial isolation, and the role of additional contributing factors and/or complicating agents should be investigated in cases of infectious coryza.

Keywords: Avibacterium paragallinarum; broilers; meningoencephalitis; otitis.

Figure 1.

Clinical signs and macroscopic lesions in 29-d-old broiler chickens with otitis and meningoencephalitis associated with Avibacterium paragallinarum infection. A. Severe torticollis. B. External ear. Accumulation of dry, yellow-brown caseous exudate on the auricular feathers (arrowhead). C. Cerebral edema and petechial hemorrhages visible on the cerebellum (asterisk), after the removal of the calvaria. Symmetrical discoloration of cranial bones, as a result of accumulation of necrotic exudate, is also present (arrowheads). D. Longitudinal section of a head. Focal accumulation of necrotic exudate within a cranial bone (arrowhead).

Figure 2.

Histologic lesions in 29-d-old broiler chickens with otitis and meningoencephalitis associated with Avibacterium paragallinarum infection. A. Heterophilic meningoencephalitis of the cerebellum. H&E. Bar = 200 μm. B. Heterophilic infiltration of leptomeninges of the cervical spinal cord. H&E. Bar = 100 μm. C. Extensive granulomatous osteomyelitis and otitis interna. A semicircular canal is still visible (asterisk), revealing edema and mild heterophilic infiltration. H&E. Bar = 1,000 μm. D. Accumulation of keratinized debris and fibrinoheterophilic exudate within the auditory canal (white arrowhead). The tympanic membrane (asterisk) is intact, and a large amount of fibrinoheterophilic exudate is present within the tympanic cavity (black arrowhead). H&E. Bar = 1,000 μm.