The Chinese Crested is a generally healthy breed but, like all breeds, is predisposed to certain genetic diseases.
These diseases can be tested for and some can be prevented entirely by screening parent animals before breeding. It is important
to test breeding stock before breeding takes place to do everything possible to prevent genetic disease from being passed
on to offspring. Though testing does not guarantee the elimination of genetic disease, it does greatly reduce the incidence
of passing on genetic disease to the next generation. Below is a brief outline of genetic diseases known to affect the
Chinese Crested breed and how they are tested for- more information about these diseases is also available on the links page.
THE MOST COMMON GENETIC DISEASES IN CRESTEDS ARE:
Progressive Retinal Atrophy (PRA & PRCD PRA) - There are at least two different types
of PRA that affect the Chinese Crested Breed. PRA causes a progressive degeneration (decay) of the retina in the eye
which gradually causes complete blindness. PRA can begin to show in the eyes in mid puppyhood to late adulthood
but is genetically present at birth if the dog has inherited the disease. A yearly CERF exam can detect active PRA but
will not detect PRA that has not yet become active within the eye. There is one form of PRA that can currently be detected
using DNA (with a blood, hair follicle or cheek swab sample) This form, known as PRCD (Progressive Rod Cone Degeneration)
need only be tested for once, as opposed to a yearly CERF exam. It is entirely possible to prevent the transmission of PRCD
PRA to offspring by testing parents before breeding. Yearly CERF exams are still needed to monitor for the form of PRA that
does not currently have a known genetic marker, along with other diseases which may affect the eye.
Keratoconjunctivitus Sicca (KCS) or Dry Eye - In this disease, the cornea and membranes of
the eye are dry and inflamed due to a reduction or absence in the water portion of the tear fluid production from the tear
glands, leaving only oil and mucus production resulting in only a gooey, yellow discharge as opposed to normal lubrication.
"Dry Eye" is the most common term used for this condition as it describes the appearance of the eye without normal tear production.
There are several causes for this disease - the most common is thought to be an auto-immune response where the dogs own immune
system damages and gradually or rapidly destroys the lacrimal (tear producing) glands. Other causes are damage to the nerves
supplying the gland from eye injury and severe, uncontrolled eye infection. (Temporary dry eye can also be caused by
a reaction to anesthesia.) This disease can show itself as either a reduction in lubrication or a total absence
of lubrication and can be seen in either one or both eyes.
Dry eye causes pain, inflammation and scarring of the cornea. If not controlled, it can lead to eventual blindness
and unremitting pain. Dry eye is diagnosed using the "Schimer Test" - a quick and painless procedure which measures the amount
of tear production using a sterile testing strip. Treatment consists of controlling infection, use of lubricating eye drops
dailey and sometimes the use of eye medication which helps the eye to produce a small amount of tear fluid. In the most severe
cases, the eye must be surgically removed to prevent pain and continued infection. This disease often presents in adulthood
and is thought to be genetically linked, though there is no known genetic marker at this time.
Patellar Luxation - Along with nearly all toy breeds, the Chinese Crested is genetically
predisposed to patellar luxation, or slipping of the knee caps. This is caused when the indentation the patella (knee-cap)
sits in is too shallow to properly form the knee joint. There are varying degrees of severity, with the moderate to severe
luxations requiring surgery to repair the knee and to prevent lameness and pain in the animal. Patellar Luxation
can be tested for by manual manipulation of the knee by your veterinarian. The OFA (Orthopedic Foundation for Animals) certifies
the absence of Patellar luxation and breeders should be able to provide proof of testing with either an OFA certifcate
or OFA form signed by their veterinarian.
Though testing of parent animals greatly reduces the incidence of patellar luxation in offspring, it is not
a guarantee that a pair of animals who have been tested clear of patellar luxation will not produce an affected puppy. Always
make sure that you have a written health guarantee from your breeder covering patellar luxation (along with other diseases
listed on this page!) for at least one year, the age at which a dog may be certified clear of patellar luxation. Most responsible
breeders provide health guarantees that are long term (4 or more years of coverage)
Legg-Calve-Perthess Disease (LCP) - LCP is the degeneration (decay) of the hip joint, specifically,
the head of the femur (the "ball" of the joint) In LCP affected dogs, the femoral head first begins to degenerate and then
heal - during the healing process the joint developes scar tissue induced malformation and no longer fits cleanly into the
hip socket, producing lameness and pain. The most common treatment for this disease is Femoral-Head Osteotomy - the removal
of the ball of the hip joint. This eradicates pain and produces free movement of the leg. It is not known exactly what causes
LCP and there is no known genetic marker, and therefor no DNA test that can be performed to detect its presence. LCP can be
tested for using a hip x-ray but is most often detected in pups at 4-12 months of age by the onset of the disease and
the resultant pain, inflammation and lameness.
Genetic Deafness and Closed Ear Canals - A small percentage of chinese crested puppies are
born deaf due to lack of pigmentation within the inner ear. This happens most often in "pink" or white animals and
animals who are predominantly
pink" or white - most especially on the head region. Deaf animals have been known to produce
deaf offspring and should never be bred. Suspected puppies as young as 6 weeks of age can be tested for deafness using
the brainstem auditory evoked response (BAER) test, a quick a painless procedure which uses an electrical read-out to show
whether or not the brain is perceiving sound.
The Chinese Crested breed has also been known to produce puppies born with closed ear canals. This can be
either unilateral (one ear) or bilateral (both ears). In many of these puppies, exploratory surgery reveals an incomplete
or absent inner ear structure. In rare instances, the inner ear was complete and hearing was restored with surgery. Puppies
born with closed ear canals should never be bred due to the lieklihood of passing on the defect.
LESS COMMON GENETIC DISEASES AFFECTING CRESTEDS:
Thyroid Disease - under or over active thyroid glands may produce symptoms that include rapid
weight loss or gain, lethargy or hyperactivity, hair loss, panting, and apetite changes. Thyroid disease can be tested for
using simple blood tests. Treatment can include medications and/or surgery.
VonWillebrands Disease (vWD) - Though not formerly considered an issue in the Chinese
Crested breed, a small number of chinese cresteds have been dignosed, largely thanks to the very broad testing panel provided
by PawsitiveID/ Pinpoint Technologies. Von Willebrand's disease (vWD) is the most common inherited bleeding disorder of both
man and animals. It is caused by a deficiency in the amount of a protein needed to help platelets (a blood cell used in clotting)
seal broken blood vessels. The deficient protein is called von Willebrand factor antigen. Dogs affected with vWD bleed and
bruise easily, have difficulty ceasing bleeding when cut or injured and can suffer internal bleeding with injuries that would
not otherwise affect a normal animal. This disease has a known genetic marker and can be tested for using DNA. Ask your
breeder for proof of DNA testing for vWD.
DNA TESTING:
At this time, only two of the diseases listed on this page have genetic markers which can be tested for. Those
diseases are the PRCD form of PRA and VonWillebrands Disease (vWD). If both parent animals are free of the gene mutations
for these diseases than all offsrping of those parents will be free/ clear by default. If a carrier animal is bred to a clear
animal, the pair may produce carriers, but they will not produce affected animals. D'Nude Chinese Cresteds believes that is
unethical to ever breed any affected animal or to breed two carriers together due to the likelihood of producing other
affected animals.
