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Choanal atresia
Choanal atresia, often referred to as CA,
is one of many congenital and presumed to be hereditary defects
in llamas. It is of little or no short-term concern to average
llama owners, but of great importance to llama breeders, and
to those llama owners who would someday like to have one or two
offspring from their female working animal(s). However, even
those who would like to own only a couple of geldings can be
affected -- both partial CA and crudely corrected CA llamas have
been sold without disclosure to unknowledgeable buyers.
Wiping out CA is not as simple as
culling producers. Choanal atresia involves at least one recessive
gene, and thus can remain hidden in the gene pool indefinitely
without the help of an affordable DNA test to detect carriers.
Interestingly, the other species afflicted
with CA is humans. Identifying CA carriers and the reponsible
genes in llamas may allow insight into the nature of the defect
in humans.
What is choanal atresia?
Choanal atresia is a congenital condition
(meaning that the llama is born with it) in which the normal
airway (between the nasal and pharyngeal areas) is blocked by
bone, membraneous tissue, or a combination of the two. Occasionally,
only one passage is blocked (unilateral) or the blockage is not
complete. Both of these conditions are referred to as "partial
choanal atresia."
CA occurs in both North and South America,
in all climates, and under many different management systems
and practices (or lack thereof). CA occurs more frequently in
llamas related to those already known to produce offspring with
CA. The combination of the preceding conditions and the obvious
familial relationships indicates that the condition is hereditary.
It has also been established that males and females are affected
with equal frequency, that there must be at least one recessive
gene involved in the inheritance mechanism, and that a CA carrier
can inherit the defective gene from either a male or a female
parent.
CA also occurs in alpacas, indicating that
the responsible mutation in lamas is probably a very old one.
CA occurs only rarely in other domestic species, and the cause
in those species is unknown. CA does occur in humans, however,
is hereditary, and is often accompanied by other defects.
What happens to a cria born with choanal
atresia?
Although mild partial CA crias may merely
seem less active than their peers or even go undetected until
adulthood when work demands result in inexplicable shortness
of breath, a full (bilateral) CA cria must breathe through its
mouth, and thus cannot nurse without also getting milk into its
lungs, which in turn results in life-threatening pneumonia. A
CA cria's nostrils usually flare with each breath. It may gasp
for air, or it may barely have its mouth open, leading the observer
to incorrectly deduce that it is breathing through it's nose.
One method of quick diagnosis is to hold the mouth and one nostril
tightly closed and see if the remaining nostril fogs a mirror
(at room temperature); the procedure is then repeated with the
other nostril. A blocked nasal passage will not be able to fog
up a mirror, and a CA cria will also be stressed (and quite distressed)
by this test.
CA crias frequently have other defects, such
as heart and other internal organ defects, missing kidney or
portions of the reproductive system, partial or complete lack
of olfactory structures (that is, the cria cannot smell), and
occasionally polydactyly (extra digits).
Although there are two surgical techniques
to provide the cria with a nasal airway, neither are entirely
satisfactory. One is a crude and difficult-to-control technique
that involves punching holes in the blockages via the nostrils
under sedation. If the cria is lucky enough not to be speared
through the brain by the "tool," tubes are inserted
into the nostrils so that the new openings will not heal shut.
The long-term problem with this technique is that at birth, the
tool used can only be as big around as a pencil. This does not
provide an adequate airway for an adult llama to pursue a normal
life.
A second technique for correction is a surgical
reconstruction of the nasal passages. This provides an adequate
airway, but involves months of tedious and difficult aftercare
to ensure proper healing without infection. In addition, the
necessary approach disturbs four growth plates, and so the adult
corrected llama has a shortened upper jaw. This means that molars
do not meet correctly, incisors jut out beyond the bite plate
and upper lips, and comfortable use of a halter is compromised.
This second surgery is very expensive, apparently is a painful
result for the adult llama, and is only used for those llamas
necessary for CA research breeding herds.
Not yet tried (to our knowledge) is opening
the nasal passages using an endoscope and laser surgery, allowing
the llama's skull growth plates to mature, and only then proceeding
with surgical reconstruction.
When one considers the drawbacks to the current
methods of surgical correction and the important fact that a
CA cria stands a good chance of also having other, very serious
undiagnosed defects and may die anyway (after a crummy life of
intestive medical treatments), the most humane choice usually
is, unfortunately, immediate euthanasia.
How frequently does choanal atresia occur?
The only universally accepted answer is that
estimates vary!
- One source states that 25% of all alpaca
deaths in South America are due to choanal atresia, and that
in South America, all alpacas are considered probable carriers.
(note: This is patently ridiculous, as any simple, lethal
recessive gene with a 100% carrier rate would result in 25% CA
crias, who then die ... and so then all the other alpacas would
have to be immortal for that math to be accurate! Nonetheless,
we were contacted by a prominent camelid researcher, requesting
that we locate the study and original data for him ... which
proved to us, once again, that people with DVMs and PhDs don't
necessarily have any common sense.)
- One North American study compiled data showing
that choanal atresia accounted for 10% of all congenital defects
seen at the institutions contributing to the survey.
- Of singly-tabulated defects, only umbilical
hernias (a non-lethal defect) occured more often than CA.
Another North American study estimated that
a CA carrier bred to randomly selected llamas would produce a
CA cria in one out of 30+ matings. This implies that, depending
on the mode of inheritance, CA might be carried by anywhere between
one in eight and one in three llamas in the population. Current
evidence favors two forms, each caused by a different single
recessive gene (and perhaps also activated by a single copy of
a separate, dominant gene), and thus a one-in-four figure might
apply, but at a rate approaching something more like one-in-eight
(each carrier would have to be of the same type to produce a
CA cria). By extrapolation, then, CA would occur in one out of
every 240 births.
Some informal surveys indicate that this is
a fairly reasonable estimate. Some breeders (particularly those
fortunate enough not to have had CA crias) think that estimate
is too high. Several others with large herds (as well as recent
informal surveys) agree on a 1-in-100 births figure. Of course,
one thing that is certain is that figures gleaned from
breeder surveys and from institutional databases are definitely
skewed (low) by those who choose not to report or reveal the
birth of CA crias.
What llamas are known producers of CA?
Unfortunately, the subject of CA producers
is a big can of political worms. In the past, when fancy woolly
llamas had pricetags of five and six figures and stud fees were
commonly $1000 to $6000, any CA cria meant a large outright economic
loss. Neutering the parents was simply not considered by the
investment-driven llama multipliers. The vast majority of CA
producers were simply bred to different llamas in hopes that
another choanal atresia cria would not be the result. Big-ticket
stud owners made threats, paid what amounted to hush-money, objected
to making registry records public (which -- back then when all
females were kept pregnant all the time -- would show mysterious
gaps in a female carrier's production followed by matings to
a different male), and made public statements that CA was carried
only by females or could not possibly have a genetic basis. If
the cria was born on their own farm, the policy was "shoot,
shovel, and shut up." CA-producing females were frequently
the first to be sold off (without disclosure) to unsuspecting
buyers. Unfortunately, during this time, some very prolific and
popular studs were also carriers, and thus the frequency of choanal
atresia carriers within the llama population markedly increased.
The current situation is different -- llama
prices are a lot lower, for one thing -- but economics still
gets in the way of the truth. There is an oversupply of llamas,
and so multipliers (and real breeders) are finding it difficult
to meet the llama bills by selling the llamas that they raise.
Many are frightened that if they reveal one of their animals
had a CA cria, nobody will buy any of the related llamas on their
overcrowed farm, or related animals on their friends' farms.
Those who provide stud service have spent a lot of money to advertise
and promote their stud, have taken in (and already spent) a lot
of money from stud fees, and thus are frequently unwilling to
lose their ride on the gravy train (or merely risk lawsuit from
past customers) by revealing carrier status.
Some people do disclose the names of CA producers
that they own, or owned and have since neutered and sold. For
now, this is the best a prospective buyer can hope for. Once
a test for CA carriers has been developed, a buyer would be foolish
to consider purchasing any llama (other than a gelding or spay)
that has not been tested.
How can I make sure that I don't by a CA
producer?
Until a test becomes available to determine
carriers, you cannot be sure. For now, llama breeders are limited
to stacking the odds against it through knowledge of the llama's
geneology.
Everybody makes their own decisions regarding
how much risk they are willing to take -- that is, how many generations
back they feel comfortable allowing a known CA producer to appear
in their breeding stocks' pedigrees. Some people will not accept
a known CA producer anywhere in the pedigree of a breeding animal;
others are comfortable with 3-5 generations; still others are
content to own and breed half and full siblings to known producers.
Those who breed close relatives of CA producers such as full
siblings and normal-appearing offspring of known producers are
increasing the odds that they or their progeny's buyers will
end up with a CA cria. Virtually all ethical breeders agree that
this is an irresponsible practice unless the resulting offspring
are neutered.
The one exception to "staying away from
close relatives" is throroughly researched male ancestors
of a CA producer. Those studs who have already had numerous normal
offspring -- particularly by any females who later produced a
CA cria or carrier -- are at a very low risk for being carriers
themselves. Matings to 30+ different females would be a bare
minimum; 60 or more healthy cria would be a reasonable indication
that the stud is not likely to be a carrier. It is possible for
a stud to be a carrier and to not produce a CA until after 100
or more offspring, but the odds against it are rather high. Offspring
of male ancestors who pass this close scrutiny (unless they are
out of the same female that produced the carrier) are also comparatively
low risks.
It would be inappropriate to test any descendent
of a CA producer in this manner because it not only risks making
more carriers, but adds to the current oversupply of llamas.
However, male ancestors may have produced enough offspring
to make on-paper research possible without any actual impact
on the llama population.
How do I make safe mating choices to be certain
that I don't have a CA cria?
Until a test for carriers is available, you
simply can't be certain. If the possibility of a CA cria is too
devastating for you to consider, then the only thing you can
do is to not breed llamas, or at least not breed llamas until
the carrier test has been developed.
You can attempt to breed only from llamas
who are not related to CA producers, but this practice is only
as good as your knowledge. Furthermore, your knowledge is only
as good as your sources' honesty -- owners of the most prolific
CA producers tend to keep tightly sealed lips and may lie when
asked direct questions. Finally, a CA carrier female may go an
entire lifetime without producing a CA cria. Carrier status is
more easily passed undetected through female lines by virtue
of the fact that the females produce fewer offspring.
What should I do if a CA cria is born in
my herd?
This will vary somewhat depending on your
proximity to adequate veterinary diagnostic facilities, but the
primary concern should be to first confirm that you do
in fact have a CA cria. A cria may also have trouble
breathing for other reasons, and the mirror test can be conducted
improperly, giving both false hopes and fears. Positive diagonsis
is by contrast radiography (the cria must be sedated) or endoscopy.
You can aid in choanal atresia research
by obtaining a minimum of 5ml whole citrated blood samples for
DNA research (Texas A&M will in turn extract leucocyte pellets
-- which have very high quality DNA -- from the samples and freeze
them).
If you do not own both parents or are uncertain of the cria's parentage, obtain
5ml EDTA whole blood (in a lavendar top tube) so that you can
have DNA fingerprinting done through the International
Lama Registry for parentage confirmation (or exclusion). Parentage
of defective crias produced from outside breedings is often contested
or denied by the stud owner. You need solid (DNA) proof of parentage
to protect you from liability and slander suits (and possibly
fulfillment of a breeding contract or a refund). And if by some
chance the sire is actually an animal you own, such as a young
male on your farm that you thought was too young to breed or
a llama you were sure couldn't ever get over or through his fence,
then you will have important, invaluable information about your
own animals and their genetic material.
After obtaining adequate samples, euthanize
the cria (unless you have chosen to pursue corrective surgery)
and allow the mother some time with the body to help her accept
her loss. If you are not donating the cria's body for research
(we do recommend at least obtaining a necropsy with a written
report), allow the body to remain until the mother walks away
on her own. Remember to milk out the colostrum from the mother
and freeze it. You or someone else in the area may need it someday.
It is courteous to inform all buyers of descendants
from the CA producing parents, and the owners of all grandparents
of the CA cria. If you do not own the stud, inform the stud's
owner immediately and allow him or her to inform anyone who owns
relatives of the stud. Contacts should be made prior to any public
disclosure of the CA producer(s) that you own. However, none
of these people has a right to request or demand that you make
no public disclosure, or to restrict the information you disclose.
As long as you have a written necropsy report and parentage confirmed
by DNA analysis, you may disclose all facts about the situation
without fear of lawsuit (some stud owners do threaten to sue,
but no lawyer would take the case as long as you have the necropsy
report and the DNA analysis).
Public disclosure of CA producers you own
(registered name and ILR number) will help other people make
their breeding and purchasing decisions. Public disclosure may
turn up other related producers and make the line of inheritance
clear, absolving many noncarrier relatives of undeserved blame.
We do not recommend listing grandparents of CA producers in a
public forum because those animals may be wrongly misunderstood
to be the carriers themselves. Good forum for disclosure are
some of the lama listservers; you may also disclose on this page
(below) by emailing us the information and asking that we post
it, or you may do so on your own webpage (we'd be happy to link
to it).
If you do not own the sire, you should not
disclose his name or owner unless you have (1) DNA fingerprinted
the cria, sire and dam and thus proven beyond doubt that the
named stud is in fact the sire or (2) received written permission
from the sire's owner. The ramifications, if you chose to ignore
these precautions, could be a very expensive lawsuit along with
political blacklisting that is very difficult for a breeder to
survive. Believe us -- it HAS happened to many people.
If a CA cria is born in my herd, what should
be done with the parents? How about other relatives?
Virtually no one will argue that both parents
of your CA cria should be immediately and permanently
removed from the gene pool, preferrably by sterilization. More
than a few people will balk at such a suggestion, however, if
it is their breeding stock that is on the line.
This is what we have done, and recommend:
The male parent is castrated. If you will retain both ownership and possession
of the female parent, spaying may not be necessary (for some
females, being open is stressful and/or distracting, and those
llamas should be spayed if possible). If the female might
be sold, leased or loaned, she is spayed first. Even
if you sell her to a good friend whom you can trust, situations
change and she may later be resold, this time to someone who
does not understand (or care) about the important responsibility
breeders have to cull carriers of genetic defects, or circumstances
(such as death or mental incapacity) may prevent your good friend
from making full disclosure.
A conscientious breeder with adequate funds
(and space) could theoretically opt to leave a superior animal
intact and not breed him or her until the carrier test is developed.
Potential mates could then be screened and only noncarriers used
to produce a worthy, noncarrier replacement for the carrier parent;
all carriers produced in the process would be spayed and castrated.
However, in practice, this would only be worth considering if
the producer is undeniable superior and irreplacable in all other
aspects. Between the expense of having to test all offspring,
the numerous spays that would be necessary, and -- if the carrier
is male -- the lost production from all of the (presumably excellent)
noncarrier females tied up in the effort to produce that one
replacement, using any CA carrier for breeding in this manner
would not be economical. It also would not be approved of by
those who are unable to understand that any carriers produced
would be sterilized, and thus a breeder might suffer further
economic loss through a needlessly damaged reputation. And, most
importantly, the necessary test is still in development -- and
funding is proving more and more difficult to obtain for political
reasons.
Other relatives are a tricky matter. As outlined
above, the research possibilities for ancestors are much different
than for descendants. Decisions are best made on a case-by-case
basis. A good policy for immediate descendents is to not
breed them until a carrier test is available so that their status
can be determined.
How can I protect myself and minimize my
own economic losses in case one of my llamas has a choanal atresia
cria?
- Select and breed from only those animals
with a valid end use. Llamas who can no longer breed but can
pack, show, drive, or fulfill some other function will retain
value.
- Preserve females' physical integrity by not
impregnating prior to maturity (see female
breeding age). Females who are not bred until after physical
maturity can still pack, show, or drive, and thus retain much
of their value.
- Do not breed your female to an outside stud
or purchase a bred female without a contract specifically outlining
recourse in the event of a choanal atresia cria ("genetic
defect" is not sufficiently clear wording).
Be sure the accepted method of proof is also in writing.
- Do not offer stud services or sell bred females
unless you cannot afford to provide a full refund in the case
of CA births. Designate what proof will be necessary (eg, documentation
of necropsy by a veterinarian and DNA parentage verification)
in the event of an alleged CA cria. It may sound overly cautious
to insist on parentage verification and veterinary documentation,
but what if the father is actually a weanling male on the dam
owner's farm? It has happened. What if the dam owner or his/her
veterinarian had never seen a CA cria and mistakenly put down
a cria with pneumonia? You certainly wouldn't want to castrate
your stud and refund monies in either case. For both provided
stud service and sales of bred females, also put in writing what
steps both parties will take regarding the female parent -- any
refund by the stud owner should be contingent on permanent, surgical
removal of the dam from the gene pool.
- In both sales and purchase contracts, include
a "full disclosure" clause that entitles both parties
to full disclosure regarding named defects in the particular
animal's history (including relatives) before sale, and also
indefinite rights by both parties to futher disclosure in the
event that additional information becomes available after the
sale.
- Be aware that you can't realistically expect
a purchase contract to guarantee a given animal is not a carrier
of choanal atresia. Discovery of genetic defects that cannot
be tested for (and that's all genetic defects in llamas
at this time) is one of the many risks inherent in the process
of breeding animals. For the same reason, do not offer contracts
that guarantee a given animal is not a carrier of choanal atresia
unless you can afford to fulfill those contracts to all buyers'
complete satisfaction.
- Once a test for carriers becomes available,
demand that all llamas (except geldings and spays) be tested
prior to purchase (have blood drawn in your presence by a veterinarian
you've hired and mail the sample yourself), and also insist that
any deposit monies be fully refundable if the animal in question
is found to be a carrier. You may wish to waive testing if both
parents have been tested and found not to be carriers, however,
be aware that the possibility of record or identity falsification
will exist, and that false positive and false negative results
occur in other tests. The true accuracy of a CA carrier test
won't be known until after years of use.
How can I help find the genetic marker and
develop a test for choanal atresia?
- Send blood samples from the cria and both
parents to DNA researchers at Texas A&M. Chilled whole citrated
blood (5ml minimum) is preferred unless your vet is able to extract
frozen leucocyte pellets (5ml). Ship chilled samples on melting
ice at 4° C (do not ship over a weekend or a holiday) and
call if you or your vet have other questions: (409) 862-4402
L. Garry Adams
Department of Veterinary Pathobiology
Medical Research Building, Foom 103
Hwy 60 W
College of Veterinary Medicine
Texas A & M University
College Station, TX 77843-4467
- Provide full known geneology of both CA-producing
parents to researchers when providing samples or a cria. Disclose
names of CA-producing llamas in appropriate public forums and
state that you have provided geneology to researchers -- this
example encourages others to follow suit.
- DNA fingerprint any CA cria with questionable
parentage, or who was the product of one or more llamas that
you do not currently own.
- Donate money to organizations currently funding
choanal atresia research, such as Morris
Animal Foundation, or make donations directly to Oregon State
University (make checks payable to The OSU Foundation ).
Be sure you make a notation that the money is to be used for
choanal atresia research in llamas.
Morris Animal Foundation
45 Inverness Drive East
Englewood, CO 80112-5480
Oregon State University
Dean's Office
College of Veterinary Medicine
200 Magruder Hall
Corvallis, OR 97331
Based on what is already known about the lamoid
genome and similar research in other species, it can be stated
with reasonable accuracy that it will take three to five years
to locate the genetic marker for choanal atresia. Once the marker
has been found, however, it will take relatively little time
to develop a test that will identify CA carriers.
After a test becomes available, the burden
of eliminating CA from the gene pool rests squarely on the shoulders
of breeders and buyers. Within two generations, noncarrier offspring
from any superior carrier parents can be selected as substitute
breeding stock and there should be no reason to breed from a
CA carrier. However, without incentive from buyers and preferably
changes in registration policy, some people will refuse to test
their breeding stock and may even knowingly continue breeding
carriers.
Although DNA research is not cheap, unlike
most other very important llama research, once the marker for
CA has been found and the test developed, there will be no more
research expense. Another point is that even with our modern
technology, we can only learn how best to reduce occurances and
provide treatments for most other llama afflictions -- total
prevention is not an option. Genetic defects, such as choanal
atresia, can be all but eradicated. For these two reasons, the
money spent on choanal atresia research is not wasted, but rather
is well-spent towards a tangible, permanent end.
The good news is that with education, effort,
commitment, and a valid carrier test, llama breeders could be
successful in completely removing choanal atresia from the North
American registered llama gene pool. Without a test -- and lack
of funding and cooperation are the major reasons why there IS
no test yet -- carriers will continue to spread the genetic material
for CA throughout the gene pool, eventually making eradication
impractical or impossible. Those who have experienced the joy
of having healthy llama companions and yet have also seen the
heart-wrenching struggles of a CA cria followed by the disappointment
of euthanizing the newborn and then neutering one or more of
their carefully selected breeding animals know more than anyone
just how important a CA carrier test is to the future health
and viability of the entire llama species.
Further reading:
Medical information
- Choanal Atresia,
Smith and Timm, Llamas Magazine, Nov/Dec 1994
- Congenital/Hereditary Conditions (in Medicine and Surgery of South American Camelids),
Fowler, 1989
- Congenital Defects in the Llama (in Veterinary Clinics of North America: Update on
Llama Medicine), Leipold, Hiraga, and Johnson, 1994
Opinion pieces
- The Problem with Choanal Atresia, McGrath, Llama Life II, Winter 1997-98
Disclosures:
On December 22nd, 1997, we had a CA cria born
on our farm. We owned both parents at the time.
- Sire: Hidden Valley Silverhawk, ILR #59424
[has been castrated; all decendents have been neutered]
- Dam: Rocky
Mountain Kiowah, ILR #118507 [has been spayed; no other offspring]
If you would like disclose of any choanal
atresia producer(s) that you own for inclusion
in the above list, email
for details about submitting information and proof of ownership.
Your name will not be included in the posting unless you request
it.
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