Delaware Valley Chinese Crested Club, Inc. -            Dedicated to the Chinese Crested Breed
HEALTH


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Eye Diseases and the Chinese Crested 

    The Chinese Crested is primarily affected by two types of eye diseases; Progressive Retinal Atrophy (Generalized PRA & PRCD) and Primary Lens Luxation (Anterior Lens Luxation & Posterior Lens Luxation).  
Three of the four forms of eye disease can be preventable if Genetic Testing for PRCD & Primary Lens Luxation is done on the parents BEFORE any breeding. A dog that has been genetically tested and the results are normal, the dog is clear of the three eye diseases.  A dog that has been genetically tested and the results are carrier, the dog is will not come down with the eyes disease, but does carry the gene which can pass onto its offspring. A dog that has been genetically tested and the results are affected, the dog is will come down with the eyes disease, and will pass onto its offspring.  A responsible breeder always has the proper genetic testing done before any breeding.  Ask the breeder to see all appropriate genetic testing forms for the parents prior to acquiring your new family member. Do not worry about offending the breeder- all proper testing is the responsibility of the breeder! If they do not test, do not acquire your new family member from them!   

Progressive Retinal Atrophy - Is a group of genetic diseases, 14 in total seen in various breeds of dogs. It is characterized by the bilateral degeneration of the retina, causing progressive vision loss culminating in blindness. The condition in nearly all breeds is inherited as an autosomal recessive trait.  There is no treatment. Blindness caused by Generalized PRA is a slow process resulting from the loss of photoreceptors at the back of the eye. PRA is detectable years before the dog shows any signs of blindness. PRA is inherited as a recessive trait. This means a disease gene must be inherited from each parent in order to cause disease in an offspring.   There are two forms of inherited PRA that can affect the Chinese Crested Breed; 

Generalized PRA and Progressive rod-cone degeneration (PRCD).  Both are diagnosed with different testing.   

Generalized PRA-  Is the most common type and causes atrophy of all the neural retinal structures. Generalized PRA can be divided into either dysplastic disease, where the cells develop abnormally, and degenerative, where the cells develop normally but then undergo a damaging change. PRA can be further divided into affecting either rod or cone cells. Rod cells detect shape and motion, and function in dim light. Cone cells detect color and definition, and function in bright light.  Diagnosis of Generalized PRA - Routine eye examination can suggest the presence of progressive retinal atrophy. The veterinary ophthalmologist examines the retina with an instrument called an indirect ophthalmoscope or a definitive diagnosis typically is made by a veterinary eye specialist using an Electroretinogram (ERG) to measure the retina’s ability to respond to light. During this examination, one electrode is placed on the dog’s cornea, and neutral electrodes are placed on the skin around the eye. The results of this test are conclusive.  This testing should be done annually as Generalized PRA can emerge at any point in the dog’s life.  Treatment Options for Generalized PRA - There is no way to reverse or to treat Progressive Retinal Atrophy, or the total loss of vision that inevitably accompanies it.   
Prognosis for Generalized PRA - Progressive Retinal Atrophy will eventually result in blindness. There is no cure, prevention, or treatment currently available. However, with minor environmental accommodation (avoid rearranging the furniture, etc.), most affected dogs adjust very well to vision loss and can live long and healthy lives, particularly if their sight deteriorates gradually.  

Progressive rod-cone degeneration (PRCD) - Is a disease with normal rod and cone cell development but late onset degeneration of the rod cells that progress to the cone cells. It is inherited as an autosomal recessive trait.   
Diagnosis of Progressive rode-cone degeneration- Routine eye examination cannot determine if a dog has the PRCD form of PRA. There are DNA blood tests available, to determine if dogs are likely affected with PRA, are likely carriers for PRA, or are not likely carrying the PRA gene. OptiGen, LLC offers testing.  Since this is a genetic testing, there is only the need to test once in the dog’s lifetime.  If both parents are tested NORMAL, all offspring are Normal by default, there is no need for testing as the offspring are clear of the disease.  
Treatment Options for Progressive rode-cone degeneration - There is no way to reverse or to treat Progressive rod-cone degeneration, or the total loss of vision that inevitably accompanies it.   
Prognosis for Progressive rode-cone degeneration - Progressive rod-cone degeneration will eventually result in blindness. There is no cure, prevention, or treatment currently available. However, as with Generalized PRA, with minor environmental accommodation (avoid rearranging the furniture, etc.), most affected dogs adjust very well to vision loss and can live long and healthy lives, particularly if their sight deteriorates gradually.    


Primary Lens Luxation - Primary lens luxation is an inherited disorder in which the zonules or suspensory fibers degenerate. Although the underlying reasons for the lens luxation are not well understood, inflammation or a defect in the zonules may play a role. With primary lens luxations, both eyes are prone to dislocation of the lens.   There are two forms of inherited PLL that can affect the Chinese Crested Breed; 

Anterior Lens Luxation and Posterior Lens Luxation.      
Anterior Lens Luxation - Anterior Lens Luxation, the lens pushes into the iris or actually enters the anterior chamber of the eye. This can cause glaucoma, uveitis, or damage to the cornea. Uveitis (inflammation of the eye) causes the pupil to constrict (miosis) and trap the lens in the anterior chamber, leading to an obstruction of outflow of aqueous humour and subsequent glaucoma. Surgery to remove the lens has a higher success rate when it is performed before the onset of secondary glaucoma. 

Posterior lens luxation - Posterior Lens Luxation, the lens falls back into the vitreous humour and lies on the floor of the eye. This type causes fewer problems than anterior lens luxation, although glaucoma or ocular inflammation may occur. Surgery is used to treat dogs with significant symptoms. Removal of the lens before it moves to the anterior chamber may prevent secondary glaucoma.   

Diagnosis of Primary Lens Luxation- Diagnosis is made by discovery of the lens in the anterior chamber, on the floor of the vitreous cavity, or no longer centered in the normal position. A veterinarian may perform the following diagnostic tests: ·         A thorough eye examination - Fluorescein staining to rule out corneal ulcers -        Tonometry to detect glaucoma or low intraocular pressure (IOP) -  Examination with a slit lamp to localize the position of the lens and the depth of the anterior chamber  - Assessment of the front portion of the eye for signs of inflammation (uveitis) - Examination of the retina - A complete blood count and serum biochemistry tests - Serology/immunologic tests for the various causes of uveitis in dogs - Electroretinogram (ERG) to assess the potential for vision in animals with glaucoma There are DNA blood tests available, to determine if dogs are likely affected with PRA, are likely carriers for PRA, or are not likely carrying the PRA gene. Orthopedic Foundation for Animals offer testing.  Since this is a genetic testing, there is only the need to test once in the dog’s lifetime.  If both parents are tested NORMAL, all offspring are Normal by default, there is no need for testing as the offspring are clear of the disease.  

Treatment Options for Primary Lens Luxation - The treatment of Lens Luxation varies depending on the location of the lens, the presence of acute glaucoma and the potential for vision. The main goals of treatment include lowering the pressure within the eye (IOP), surgical removal of anteriorly luxated lenses (in eyes with a potential for vision), and treatment of underlying causes. Acute luxations or subluxations are considered emergencies and must be treated at once.   The first step is to assess the eye to see if vision is possible. If the luxation and elevated IOP have been present for more than 48 hours, the eye may be permanently blind. If the luxation is recent or acute, and if the glaucoma is not severe, and the retina and optic disc still look healthy, then there may be a reasonable chance of saving vision with surgery.   Treatment may include the following: Control of glaucoma - IOP must be lowered immediately within a few hours with osmotic agents, topical or oral antiglaucoma medications, and topical anti-inflammatory agents. Surgical removal of the lens is considered when the lens is in the front chamber of the eye, especially once the glaucoma is under control. Control of the anterior uveitis. Treatment of uveitis often involves the use of topical anti-inflammatory agents, and oral anti-inflammatory agents. Removal of the eye may be necessary if the eye is blind and painful.   

Prognosis for Primary Lens Luxation - Following initial therapy, the pressure within the eye (IOP) is monitored closely, and all medications are continued at home. After removal of the lens an initial recheck should occur. Chronic monitoring of IOP is indicated because dogs that are prone to Primary Lens Luxation are also prone to glaucoma, Monitoring the lens position is also important if the lens is loose, but still in place. Your veterinarian may instruct you to watch for signs of glaucoma such as redness, eye swelling, pain and squinting. If a Primary Lens Luxation is diagnosed in one eye, the other eye must be closely monitored for degeneration of the zonules and loosening of the lens. Most cases of lens luxation cannot be prevented in the dog.   


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Luxating Patella and the Chinese Crested

The Chinese Crested can be affected with Luxating Patellas (Patella Luxation). 
 
Description- The patella, or kneecap, is part of the stifle joint (knee). In patella luxation, the kneecap luxates, or pops out of place, either in a medial or lateral position.
 
Symptoms - Although the luxation may not be present at birth, the anatomical deformities that cause these luxations are present at that time and are responsible for subsequent recurrent patella luxation. Symptoms vary dramatically with the degree of luxation.
In grade 1 dogs may not show symptoms early on, but older animals may exhibit sudden signs of lameness.
In grades 1 and 2 Lameness is evident only when the patella is in the luxated position. The leg is carried with the stifle joint flexed but may be touched to the ground every third or fourth step at fast gaits.
In grades 3 and 4 puppies may show signs of abnormal hind-leg carriage and function from the time they start walking. Grade 3 and 4 dogs exhibit a crouching, bowlegged stance with the feet turned inward and with most of the weight transferred to the front legs.
Pain is present in some cases. Most dogs; however, seem to show little irritation.
Lateral luxation in Chinese Cresteds is most often seen late in the animal's life, from 5 to 8 years of age. Most lateral luxations are grades 1 and 2, and the bony changes are similar, but opposite, to those described for medial luxation. The dog has more functional disability with lateral luxation than with medial luxation. In mature animals, signs may develop rapidly and may be associated with minor trauma or strenuous activity.
 
 
Diagnosis - Physical examination.Severity of Luxating Patella is determined by palpation of the knee joint and is classified from 0 (normal) to 4 (severely affected) as follows;
Grade 0 : Normal
Grade 1: The patella can be pushed out of the groove but spends most of time in the groove
Grade 2: The patella approximately half the time in the groove and half the time out of the groove. It can easily be manipulated in or out but has no tendency to stay in either position.
Grade 3: The patella spends almost all the time outside the groove and with pressure can be pushed back into the groove.
Grade 4: The patella spends all the time outside the groove and even with pressure the patella cannot be pushed back into the groove.

Treatment & Prognosis - The prognosis for a Grade I patella luxation is very good. These dogs may not need surgery. However close observation for signs of worsening is important. If surgery is indicated and performed early on, most Chinese Cresteds regain normal functionality.
The prognosis for Grades 2 and 3 depends on how much arthritis and malformation have occurred. If caught and treated early, both have a good to excellent prognosis. If there is significant bony malformation or arthritis, the prognosis is guarded to fair.
The prognosis for Grade 4 patella luxation is guarded. Most of these dogs have moderate to severe bony malformations and significant arthritis. If correction is performed, it is important to initiate early physical therapy to help restore function.
 
Inheritance - Patella luxation should be considered an inherited disease.Trauma or injury can also cause patella luxation.