Camelidae and Cervidae Congenital Respiratory Defects – NAVLE Study Guide

Overview and Clinical Importance

Congenital respiratory defects in camelids (llamas, alpacas, vicunas, guanacos) and cervids (deer, elk, moose) represent significant clinical challenges in veterinary practice. These defects primarily affect the upper respiratory tract and can be life-threatening in neonates. Understanding these conditions is critical for the NAVLE because camelids are obligate nasal breathers, making any obstruction of the nasal passages potentially fatal.

The two most clinically significant congenital respiratory defects covered in this guide are choanal atresia (failure of the posterior nasal openings to develop) and maxillofacial dysgenesis (wry face/wry nose), which involves lateral deviation of the facial bones causing airway obstruction. Both conditions require prompt recognition and appropriate management decisions.

Choanal Atresia

Definition and Embryology

Choanal atresia (CA) is a congenital defect resulting from the failure of the posterior nasal openings (choanae) to communicate with the nasopharynx. During normal fetal development, the nasal cavity and nasopharynx develop as separate cavities that eventually join at paired openings called the choanae. In choanal atresia, the buccopharyngeal membranes fail to completely rupture during the early second trimester, leaving membranous or bony obstructions over one or both nasal passages.

Species Incidence and Prevalence

Types of Choanal Atresia

Choanal atresia can be classified based on laterality and composition of the obstruction:

By Laterality

• Bilateral choanal atresia: Both nasal passages blocked. Life-threatening in obligate nasal breathers. Most commonly reported form in camelids.
• Unilateral choanal atresia: One nasal passage blocked. Animals may survive to adulthood with minimal respiratory impairment. Often detected incidentally.

By Obstruction Type

• Membranous atresia: Soft tissue membrane blocking the opening. Potentially amenable to surgical correction.
• Bony atresia: Bone or cartilage blocking the passage. More challenging to correct surgically.
• Mixed atresia: Combination of membranous and bony obstruction. Most common type overall.

Clinical Signs

Bilateral Choanal Atresia

Signs are present immediately at birth or within the first hours of life:

• Severe respiratory distress at rest
• Open-mouth breathing with marked nostril flaring
• Characteristic cheek ballooning as cria attempts to force air around soft palate
• Cyanosis that improves with crying (opens oral airway)
• Inability to nurse without gasping
• Milk aspiration during nursing attempts
• Rapid development of aspiration pneumonia

Unilateral Choanal Atresia

• May be asymptomatic or show mild signs
• Increased respiratory rate, especially with exertion
• Unilateral nasal discharge or mucoid rhinorrhea
• Open-mouth breathing during stress or exercise
• May survive to adulthood undetected

Diagnostic Approach

Early diagnosis is critical in bilateral cases. Multiple field tests can confirm the diagnosis:

Field Diagnostic Tests

Advanced Diagnostics

• Computed Tomography (CT): Gold standard for definitive diagnosis. Shows vomer thickening, choanal airspace obstruction, and differentiates membranous from bony atresia.
• Contrast Radiography (Rhinography): Radiopaque dye instilled into nasal cavity demonstrates blockage at posterior choanae.
• Endoscopy: Direct visualization of atretic plate; challenging in small neonates due to narrow nasal passages. A 6mm scope may pass in crias.

Associated Congenital Abnormalities

Choanal atresia frequently occurs as part of a syndrome with multiple malformations. Research suggests similarities to CHARGE syndrome in humans (CHD7 gene involvement). Associated defects include:

• Unilateral or bilateral renal agenesis (kidney absence)
• Cardiac defects (ventricular septal defects common in camelids)
• Wry face (maxillofacial dysgenesis)
• Cleft palate
• Polydactyly
• Angular limb deformities

Treatment and Prognosis

Maxillofacial Dysgenesis (Wry Face/Wry Nose)

Definition and Etiology

Maxillofacial dysgenesis, commonly called wry face or wry nose (campylorrhinus lateralis), is characterized by lateral deviation of the maxilla (upper jaw and nose) to one side. The severity can range from slight (less than 5 degrees) to severe (greater than 60 degrees) deviation. The mandible may or may not have a similar deviation (campylognathia).

Proposed etiologies include:

• Fetal malpositioning: Most widely accepted theory in horses and cervids. Abnormal head position in uterus during endochondral ossification causes asymmetric bone development.
• Genetic factors: In camelids, wry face is often associated with choanal atresia and understood to be genetically linked. Arabian horses show breed predisposition.
• Premature bone fusion: CT studies suggest premature fusion of incisive bone to nasal bone on the affected side, stopping growth while the opposite side continues.

Species-Specific Considerations

Clinical Signs of Wry Face

Severity determines clinical impact:

Mild Cases (less than 15 degrees deviation)

• Cosmetic abnormality with minimal functional impact
• May have slight nasal airway restriction
• Dental malocclusion may develop requiring monitoring
• Normal suckling ability usually preserved

Severe Cases (greater than 30 degrees deviation)

• Occlusion of one or both nares
• Respiratory distress and exercise intolerance
• Lack of apposition of incisors and dental pad
• Inability to nurse effectively
• Progressive dental problems and malocclusion
• Often concurrent with choanal atresia

Diagnosis of Wry Face

• Physical examination: Visual assessment of facial symmetry; measure degree of deviation if possible
• Skull radiography: Dorsoventral view shows lateral deviation of maxillary and nasal bones; helps rule out trauma
• Oral examination: Assess dental alignment and ability to achieve proper occlusion
• Nasal airway assessment: Evaluate patency of both nares

Treatment and Prognosis of Wry Face

Other Congenital Respiratory Defects

Cleft Palate in Camelids

Cleft palate is relatively common in camelids (3% of congenital defects) and may occur with other malformations including choanal atresia.

Clinical Signs

• Coughing during or after eating
• Milk or food coming from nostrils after nursing
• Recurrent aspiration pneumonia
• Nasal discharge (often feed-colored)
• Failure to thrive

Diagnosis and Treatment

• Large clefts visible on oral examination
• Caudal palate defects may require endoscopy
• Surgical repair possible for small defects but uncommon
• Large defects usually result in early death from aspiration

Memory Aids for NAVLE

CRIA DISTRESS = "CHOANA" Mnemonic

• C - Cheek ballooning (pathognomonic)
• H - Hunger but cannot nurse
• O - Open-mouth breathing
• A - Aspiration pneumonia risk
• N - Nasal obstruction (no mirror fogging)
• A - Associated defects (check kidneys, heart)

"WRY" Rule for Wry Face Management

• W - Welfare first (severe = euthanasia)
• R - Remove from breeding program
• Y - Yearly dental checks if mild

Exam Focus: Remember: Camelids are OBLIGATE nasal breathers. This is why bilateral choanal atresia is immediately life-threatening while unilateral cases may survive. The mnemonic "NO NOSE = NO LIFE" helps remember that bilateral nasal obstruction in camelids is incompatible with survival without intervention.