NAVLE Nervous

Avian Sinusitis Study Guide

March 28, 2026 25 min read 18 views

Sinusitis is inflammation of the infraorbital sinus and represents one of the most common upper respiratory tract disorders in avian species.

Overview and Clinical Importance

Sinusitis is inflammation of the infraorbital sinus and represents one of the most common upper respiratory tract disorders in avian species. The unique anatomy of the avian infraorbital sinus, which is the only paranasal sinus in birds, creates significant challenges for diagnosis and treatment. Unlike mammals, the avian infraorbital sinus drains

dorsally into the nasal cavity, making natural drainage extremely difficult and predisposing birds to chronic infections.

Sinusitis is particularly prevalent in psittacine birds (especially African grey parrots, cockatiels, and Amazon parrots), poultry (turkeys are more severely affected than chickens), and game birds. Understanding the etiology, clinical presentation, diagnostic approach, and treatment options is essential for the NAVLE/BCSE examinations.

High-YieldThe infraorbital sinus is the ONLY paranasal sinus in birds. It has multiple diverticula extending throughout the skull and beak, and opens dorsally into the nasal conchae. This dorsal opening makes drainage difficult, predisposing birds to chronic sinusitis.

Diverticulum	Location	Clinical Significance
Rostral	Within the upper beak (maxillary rostrum)	Surgical access via rhinotheca window
Preorbital	Rostral to the eye	Common site for sinus aspiration
Infraorbital	Ventral to the eye	Visible swelling with infection; covered only by soft tissue
Postorbital	Caudal to the eye; surrounds ear opening	Can affect hearing if infected
Mandibular	Extends into caudal mandible	Difficult to access; prone to chronic infection

Anatomy of the Avian Infraorbital Sinus

The infraorbital sinus is the only paranasal sinus in birds. It is a complex, convoluted structure with six diverticula that extend throughout the head and beak:

Key Anatomical Features

Dorsal drainage: The sinus opens dorsally into the middle and caudal nasal conchae, making gravity-assisted drainage impossible
Soft tissue coverage: The lateral wall of the infraorbital diverticulum has no bony coverage, only soft tissue, causing visible facial swelling with infection
Air sac communication: The sinus communicates caudally with the cervicocephalic air sac, allowing potential spread of infection

NAVLE TipRemember "DRAINS DORSALLY" for the avian infraorbital sinus. This is the key anatomical feature that makes avian sinusitis so challenging to treat. Unlike mammalian sinuses that can drain ventrally with gravity, avian sinuses trap debris and exudate because the drainage opening is at the TOP of the sinus.

Agent	Species Affected	Key Features	Zoonotic Risk
Chlamydia psittaci	Psittacines (cockatiels, budgies, Amazon parrots); turkeys	Reportable; intracellular obligate bacterium; conjunctivitis common	YES - Psittacosis
Mycoplasma gallisepticum	Turkeys (most severe), chickens, game birds, cockatiels	Infectious sinusitis; chronic carriers; "bulgy eye"	No
Aspergillus fumigatus	All species; immunocompromised birds	Fungal granulomas; chronic debilitating disease	No (not bird-to-human)
Gram-negative bacteria	All species	Pseudomonas, Klebsiella, E. coli; often secondary to hypovitaminosis A	Varies
Avibacterium paragallinarum	Chickens	Infectious coryza; acute swelling; characteristic foul odor	No

Etiology and Pathophysiology

Predisposing Factors

Hypovitaminosis A

Vitamin A deficiency is the most important predisposing factor in psittacine birds. It causes squamous metaplasia of the respiratory epithelium, resulting in:

Thickened mucus secretions that cannot be cleared normally
Loss of ciliary function and mucociliary clearance
Accumulation of debris and bacteria in the sinus
Formation of rhinoliths (concretions of debris)
Degeneration and abscessation of choanal papillae

High-YieldHypovitaminosis A is classically associated with all-seed diets, which lack vitamin A, iodine, and calcium. Always obtain a complete dietary history in any bird presenting with upper respiratory signs. Blunting or loss of choanal papillae is a classic clinical sign of vitamin A deficiency.

Other Predisposing Factors

Environmental: Low humidity, poor ventilation, excessive dust, cigarette smoke exposure, ammonia from dirty substrate
Stress: Transport, overcrowding, introduction of new birds, temperature extremes
Immunosuppression: Concurrent illness, malnutrition, chronic stress
Anatomical: Choanal atresia (especially African grey parrots), trauma, foreign bodies

Infectious Etiologic Agents

Species	Characteristic Presentation	Common Etiology
African Grey Parrots	Rhinoliths common; chronic nasal drainage; may have choanal atresia	Aspergillus, hypovitaminosis A, bacterial
Cockatiels	Chronic respiratory signs; often mycoplasmal; may be subclinical carriers of Chlamydia	Mycoplasma, Chlamydia psittaci
Amazon Parrots	Bacterial sinusitis secondary to seed-based diet; vitamin A deficiency common	Hypovitaminosis A, gram-negative bacteria
Turkeys	SEVERE infraorbital sinus swelling ("bulgy eye"); may cause complete eye closure; more severe than chickens	Mycoplasma gallisepticum (infectious sinusitis)
Chickens	Milder than turkeys; rales, nasal discharge; chronic respiratory disease (CRD)	M. gallisepticum, A. paragallinarum (infectious coryza)

Clinical Signs and Presentation

Early Clinical Signs

Sneezing (often the earliest sign)
Nasal discharge (serous progressing to mucoid or purulent)
Head shaking or rubbing beak on perch
Clicking or respiratory sounds
Matted feathers around nares

Progressive Clinical Signs

Periorbital/infraorbital swelling: Visible swelling around the eyes due to the soft tissue-only lateral wall of the infraorbital sinus
Conjunctivitis: Red, swollen eyes; ocular discharge; epiphora
Sinus flaring: Visible movement of the sinus area with breathing
Proptosis: Eye bulging due to pressure from sinus distension
Dyspnea: Open-mouth breathing, tail bobbing, neck extension

Systemic Signs

Lethargy and fluffed appearance
Anorexia and weight loss
Increased sleeping
Concurrent pneumonia or airsacculitis (common)

Species-Specific Clinical Presentations

Modality	Findings	Advantages/Limitations
Radiography	Soft tissue opacity in sinuses; mineralized rhinoliths; bony lysis in chronic cases	Widely available; limited detail due to overlapping structures
CT Scan	Detailed sinus anatomy; extent of disease; bony changes; localization for surgery	Gold standard for sinus evaluation; requires anesthesia; limited availability
MRI	Excellent soft tissue detail; CNS involvement assessment	Best for soft tissue; limited availability; expensive
Endoscopy	Direct visualization of choana, trachea; sample collection; granuloma identification	Diagnostic and therapeutic; requires anesthesia and specialized equipment

Diagnostic Approach

History and Physical Examination

Essential history questions:

Diet composition (seed-based vs. pelleted with vegetables)
Duration and progression of clinical signs
Recent stressors or environmental changes
Exposure to other birds; recent additions to flock
Prior treatment attempts

Physical examination findings:

Observe from a distance first (birds mask illness)
Palpate periorbital and preorbital areas for swelling or fluid
Examine nares for discharge, swelling, or occlusion
Examine choana (best under sedation/anesthesia) for papillae blunting, discharge, or plaques
Auscultate for respiratory sounds

NAVLE TipAlways observe a bird from a DISTANCE before handling. Birds are prey animals that mask illness. Dyspnea may only be apparent at rest in a quiet environment. Watch for tail bobbing, wing flaring, neck extension, and open-mouth breathing BEFORE restraint increases stress.

Sinus Aspiration and Lavage

The sinus aspiration and lavage is the most useful diagnostic test for evaluating the infraorbital sinus:

Technique:

Sedate or anesthetize the bird (avoid eye damage during restraint)
Insert small gauge needle (25-27G) into preorbital diverticulum
Insert dorsal or ventral to the jugal arch
Aspirate any exudate for cytology and culture
Flush with 2-5 mL/kg warm sterile saline (therapeutic and diagnostic)

Sample evaluation:

Cytology: Normal = non-cornified squamous epithelium with low bacteria; Abnormal = inflammatory cells indicate sinusitis
Culture and sensitivity: Aerobic bacterial culture; consider Mycoplasma culture (difficult) or PCR
Fungal culture: If aspergillosis suspected
PCR testing: For Chlamydia psittaci, Mycoplasma gallisepticum

Diagnostic Imaging

Laboratory Testing

CBC: Leukocytosis with heterophilia; monocytosis (chronic); non-regenerative anemia (aspergillosis)
Biochemistry: Elevated bile acids/AST with hepatic involvement (Chlamydia)
Protein electrophoresis: Elevated beta-globulins consistent with aspergillosis
Chlamydia testing: PCR (combined choanal/conjunctival/cloacal swab); collect over 3-5 days as shedding is intermittent

Etiology	First-Line Treatment	Duration	Notes
Chlamydia psittaci	Doxycycline 25-50 mg/kg PO q12-24h OR injectable doxycycline 75-100 mg/kg SC/IM q5-7d	45 days	ZOONOTIC; reportable disease; uninterrupted treatment required
Mycoplasma spp.	Tylosin, doxycycline, or enrofloxacin	Variable; at least 2-3 weeks	Birds remain carriers; no cell wall (avoid beta-lactams)
Gram-negative bacteria	Enrofloxacin 15-20 mg/kg PO/IM q12h; culture-directed therapy preferred	Based on C/S; minimum 10-14 days	Address underlying vitamin A deficiency
Aspergillus spp.	Itraconazole 10 mg/kg PO q12-24h OR voriconazole; nebulization with clotrimazole/F10	Months (often 2-4+ weeks after clinical resolution)	Surgical debridement often needed; monitor liver enzymes

Treatment Protocols

General Supportive Care

Oxygen supplementation: For dyspneic birds; place in oxygen-enriched environment before handling
Heat support: Maintain 85-90°F for sick birds
Fluid therapy: SC or IV fluids for dehydrated birds
Nutritional support: Gavage feeding if anorexic
Vitamin A supplementation: IM injection initially; dietary correction long-term

Antimicrobial Treatment by Etiology

High-YieldChlamydiosis (psittacosis) requires 45 DAYS of UNINTERRUPTED doxycycline treatment. This extended duration is necessary because doxycycline only kills Chlamydia during the active replication phase, not during the dormant elementary body stage. Interrupting treatment allows the organism to persist.

Local Treatment

Sinus flushing:

Sterile saline 2-5 mL/kg, warmed
May add antibiotics based on culture/sensitivity
May require multiple treatments
Owners can be trained for at-home nasal irrigation in chronic cases

Nebulization:

Particle size less than 3 micrometers required to reach lower airways
Antibiotics: Gentamicin, amikacin (1:10 dilution)
Antifungals: Clotrimazole in propylene glycol, F10 (1:250)
Duration: 15-20 minutes, 1-2 times daily

Surgical Intervention

Indications for surgery:

Chronic non-responsive sinusitis
Fungal granulomas (aspergillosis)
Rhinoliths requiring removal
Caseous debris that cannot be flushed

Sinusotomy technique:

CT/MRI useful for surgical planning
Create window through rhinotheca/bone to access rostral diverticulum
Curette caseous material; debride granulomas
Daily wound care and flushing post-operatively

Prognosis and Complications

Prognosis

Good: Acute bacterial sinusitis with dietary correction; responds well to appropriate antibiotics and vitamin A supplementation
Guarded: Chronic sinusitis; chlamydiosis (requires 45-day treatment); mycoplasmal infections (birds remain carriers)
Poor: Systemic aspergillosis; severe bony lysis; concurrent pneumonia/airsacculitis

Complications

Permanent nasal/sinus architecture damage
Recurrent infections (especially with bony erosion)
Spread to air sacs, lungs (pneumonia)
CNS involvement (aspergillosis extension)
Beak deformity (chronic cases)

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