This is not meant in ANY way to replace your veterinarian.  Rather, this is intended to educate, so that you may be a better partner in working with your veterinarian in providing care for camelids.  Do NOT attempt to diagnosis any illness at home.  Any animal that you suspect may have a medical problem should be taken quickly to your veterinarian. 

¨NOTE THIS PAGE CONTAINS GRAPHIC PHOTOGRAPHS

Choanal atresia, just the mention of it sends shivers down the backs of almost every camelid breeder.  Most breeders have never seen an animal with choanal atresia let alone completely understand what it involves. 

Choanal atresia (CA) is one of many congenital birth defects that can affect lamoids.  Congenital simply means that it was present at birth.  A congenital anomaly can either be hereditary or can be caused due to an influence (like a toxin) during gestation.  Much of the veterinary community looks upon choanal atresia as a genetic defect although research has yet to shed much light on this condition.  OSU-CVM did research on CA but discovered that the mode of heritance is not simple recessive trait, more likely it is polygenetic with incomplete penetrance.  Now, Dr Smith has retired and I have not heard of another institution continuing the work.

So, what is choanal atresia?  To fully understand choanal atresia you need to understand the basic anatomy of a lamoid nasal and oral cavity.  During normal embryo development the ectoderm gives rise to nasal placodes which invaginate into nasal pits later deepening to form the nasal cavity and passages.  The buccopharyngeal membrane ruptures to form the embryonic mouth which later invaginates and meets with the nasal cavity at the oronasal membrane.  This normally undergoes an apoptotic event & ruptures during embryongnesis.  In the schematic drawing below, the choanae is the opening that joins the nasal cavity to the oral cavity. 

Schematic Drawing of a midline cross section of a neonatal skull.

1) Brain

2) Bony Structures

3) Soft tissue structures, including skin

4) Nasal turbinates

5) Tongue (white teeth below)

Atresia is defined as a pathological closure or a congenital absence of an opening, passage or cavity.  In the occurrence of choanal atresia the opening of the choanae does not occur.  This can occur in varying degrees from a bony structure to a membranous structure in a partial to full closure.  Additionally, choanal atresia can affect one side of the nasal cavity and not the other, or it can affect both sides in varying degree.

Why does choanal atresia matter?  Camelids are obligate nasal breathers and choanal atresia crias either have obstructed or the absence of nasal air flow.  CA crias frequently flare their nostrils while they breathe through an open mouth on inspiration and puff out their cheeks on expiration.  Often times CA crias hypoxic and have difficulty standing or nursing due to the dypsnea.  Choanal Atresia can be clinically diagnosed, by a veterinarian, on a neonate by visually observing a bony structure blocking the choanae on radiograph or CAT scan, by holding the cria's lips closed to see if the cria can breath, by holding a mirror to each nostril to check for warm air upon expiration, by passing a feeding tube through the nasal passage or by adding water to the nasal cavity to see if the water fill the cavity or empties down the choanae into the oral pharynx.  Frequently choanal atresia is accompanied by other congenital defects like wry face or heart defects.  Euthanasia is commonly recommended in the best interest of the animal.

Do NOT attempt to diagnosis choanal atresia at home.  Any animal that you suspect may have a medical problem should be taken quickly to your veterinarian.  This information is only meant to educate you about choanal atresia.

The following photos are of a cria with Choanal Atresia, some diagnostic tools (performed at WSU-CVM) and a midline dissection of the head to view the defect.

¨NOTE THIS PAGE CONTAINS GRAPHIC PHOTOGRAPHS These photos are not intended to offend anyone, rather to educate.  These images were lifted from a video camera so they are not perfectly clear.

One day old neonate taken to WSU-CVM for diagnosis of suspected Choanal Atresia.

Open mouth breathing

Water nasal test.  In this cria both nostrils filled with water and no bubbles results.  So this is a full, bilateral blockage.

Feeding Tube test.  This cria was open mouth breathing at the same time, this was not a painful exam.  The feeding tube only passed about 3" into each side.

This is a midline dissection of the cria head which reveals the thick bony structure covering the choanae.

The blue outline is where the choanal opening to the oral pharynx should be.

T1 weighted MRI saggital section. 

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Last modified: 07/22/08