Progressive Retinal Atrophy

Progressive Retinal Atrophy (PRA) is an inherited form of eye disease causing blindness. The first symptom is usually the loss of night vision. This can appear as early as 8 months of age but often does not show up until the dog is 3 to 5 years old. Owners often notice their dog is reluctant to go outside at night. In a dim room, they may not want to jump on or off furniture, and may not go up or down stairs. As the disease progresses the pupils become increasingly dilated, causing a noticeable "shine" to their eyes and the lens may become cloudy. 

Dogs do not feel any pain or discomfort with the disease, however there is no cure or treatment, so owners must learn to live with their dog's condition. As vision deteriorates, affected dogs adjust as long as their environment remains constant.

Diagnosis of PRA is normally made by ophthalmoscopic examination. This is done using an instrument called an indirect ophthalmoscope and requires the dog's pupils to be dilated by applying eyedrops. Further confirmation can be made by electroretinography. This is an electrical measurement of retinal function. The ERG can only be recorded as a response to a flash of light and accurate recording of the ERG required the dog to be anesthetized. The ERG can also be used for early diagnosis, to detect affected dogs before they show clinical evidence of the disease. In Tibetan Terriers diagnosis can be made as early as 10 months.

Since PRA is a progressively degenerative disease, it is highly recommended that dogs have their eyes examined on an annual basis, starting at approximately 6 months and continuing until 8-10 years. This is especially true of those dogs that are being used for breeding purposes, however, there is benefit to the genetic health of the breed to test all littermates and offspring as well.

Canine Ceroid Lipofuscinosis

Canine Ceroid Lipofuscinosis (CCL), also known as Neuronal Ceroid Lipofuscinosis (NCL), is an autosomal recessive disorder affecting the eyes and the nervous system.

Abnormalities are often observed starting at 4-6 years. These include mental changes such as the development of aggressiveness toward people and/or other dogs; nervousness; changes in eating habits; loss of both behavioral and house training. Affected dogs exhibit a mildly uncoordinated gait with occasional stumbling and crossing over. The lack of coordination becomes more severe as the disease progresses. They often have difficulty jumping up onto surfaces and going up or down stairs. In the later stage of the disease affected dogs fall over often and have difficulty getting back on their feet. Visual abnormalities maybe be noticed such as impaired vision under dim light conditions. Mild seizures that are often unrecognized by the owner are common as the disease progresses.

Due to the late onset of the disease, a dog may not show any symptoms until after their breeding career is finished. Fortunately, thanks to research at the University of Missouri a genetic marker was finally found and as of late January 2010 there is a DNA test available.

Hip Dysplasia

Canine hip dysplasia is a disease involving abnormal formation of the hip joints. Progressive and crippling arthritis may result. CHD is thought to be of polygenetic inheritance with environmental influence. Some things that can affect the expression of hip dysplasia are nutrition, physical activity and flooring surfaces.

Some dogs will show signs of hip dysplasia at a very young age. Others can be dysplastic and not show outward signs until middle or old age. Symptoms include less energy and movement; difficulty rising; lameness in the back legs; reluctance to use stairs (particularly to go up); reluctance to jump or stand on hind limbs; swaggering gait, bunny-hopping gait; soreness after lying down; soreness after heavy exercise.

Diagnosis is based on a physical examination and x-rays. Depending on the severity of the dog's condition, veterinarians treat hip dysplasia with either drugs or surgery. Drug therapy doesn't reverse or cure the progression of hip dysplasia, but it does offer relief from the associated pain. weight loss programs, controlled exercise, and physical therapy can also be very effective in certain cases.

Responsible breeders have their dogs xrayed with results evaluated by OFA prior to breeding.

Cataracts

A cataract is defined as any spot on the lens, regardless of size, that does not allow light to pass through. Cataracts can be confined to a single area within the lens or affect the entire structure. They were identified in dogs as early as 1925. Some cataracts are clearly visible to the naked eye, appearing as white flecks within the eye, or giving a milky-gray or bluish-white cast to the lens behind the pupil. They result in varying degrees of blindness. Aging animals often have a graying of the lens, which should not be mistaken for a cataract.

Cataracts are classified as primary or secondary. Primary cataracts usually result from a (presumed) recessive mode of inheritance and typically appear at an early age. Usually both eyes are affected, though not necessarily with symmetrical development. Primary cataracts do not always advance to cause total blindness and are sometimes associated with other ocular diseases.

Secondary cataracts are generally associated with other hereditary eye diseases where the nutrition of the lens is disturbed as in diabetes. They can also develop secondary to PRA or Lens Luxation.

Cataracts can be also be acquired as a result of trauma.

Patellar Luxation

Patellar luxation is the dislocation of the patella (kneecap). The condition can result from trauma that caused the knee to be forced out of normal alignment, but is more often genetic in nature.

The patella may dislocate toward the inside (medial) or outside (lateral) of the leg. It can affect either or both legs. The most common occurrence of luxating patella is the medial presentation in small or miniature dog breeds.

Signs of luxation may appear as early as weaning or may go undetected until later in life. Signs include intermittent rear leg lameness, often shifting from one leg to the other, and an inability to fully extend the stifle. Early in the course of the disease, or in mildly affected animals, a hopping or skipping action occurs. This is due to the patella luxating while the dog is moving and by giving an extra hop or skip the dog extends its stifle and is often able to replace the patella until the next luxation, when the cycle repeats.

There are several degrees of luxation, with the lower grade being the ability of the kneecap to pop back into place on its own and the highest grade (of four) being such severe luxation that only surgical repair can correct the dislocation.

A veterinary examination can determine if the knee structure is stable. Breeders should have breeding stock screened to check for patellar luxation. Evaluations done after the dog is 12 months old may be submitted to OFA and unaffected dogs will be issued an OFA number. Currently most TT breeders testing for patellar luxation are not taking this extra step, so OFA does not publish any statistics on the frequency of the condition in the breed.

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