genetic testing

GENETIC TESTING
SCREENING FOR HEREDITARY EYE DEFECTS

Progressive Retinal Atrophy is the hereditary eye disease of the most concern to Tibetan Spaniels.
It causes blindness. Having eyes checked by a Board Certified Veterinarian Ophthalmologist on a regular basis is currently the main method used for detecting PRA & other eye diseases & defects. Many Tibbies with PRA are diagnosed between ages 3 to 5 years. So 1 exam on a young dog cannot predict future findings. The Tibetan Spaniel Club of America recommends eye exams every 2 years. If a problems is found, there can be more in depth testing done, such as an ERG. Rechecking should be done on a schedule recommended by the ophthalmologist. The dog should not be used for breeding until & unless the problem is determined not to be hereditary PRA. That dog & close relatives should be monitored carefully.

Cases of PRA have been found in Tibbies in several Countries, including England, Sweden, Norway & the USA. The mode of inheritance has not been established. In other breeds of dogs that the mode of inheritance has been established, most are recessive, though there are a couple exceptions. More than 1 form of hereditary PRA has been found in some breeds. This includes breeds that have DNA testing available for 1 form & does not detect the genes or markers for the other form within the breed. Research is underway at the Animal Health Foundation in Great Britain for Tibetan Spaniels.

Zen Tao Tibetan Spaniels are examined by a Board Certified Veterinarian Ophthalmologist every 1 to 2 years.
Breeders who have the eyes checked will be able to provide proof by publication of their dogs in the TSCA Eye Registry,which is online on their website & available at no charge. CERF registry, which is available with a fee for certification. Or by providing a copy of the actual exam.

ORTHOPEDIC FOUNDATION FOR ANIMALS

The OFA is an organization that does evaluations for hip, elbow, & patellas in dogs & cats. They also issue certifications for cardiac & thyroid, when done by an approved lab or specialist. Their database now also includes CERF (Canine Eye Foundation Registry) certifications. Anyone can access their database & find out what dogs have been certified free of these defects & at what age. There are wonderful features on their website where you can do reverse pedigrees to find out certification status on any particular dog’s direct relatives. Hereditary defect statistics by breed are also available. To access their website go to
http://offa.org/

HIP DYSPLASIA

Even though the Tibetan Spaniel is a small breed, hip dysplasia does exist in the breed. In the most current statistics published by OFA, from Jan. 1974 through Dec. 2006, 254 Tibetan Spaniel hip X-rays had been submitted for evaluation. Of those, 6.7% were rated excellent & 8.3% were found to be dysplastic. These do not include X-rays that were taken by veterinarians where the owner did not want them submitted for evaluation as they felt the defects were obvious & did not feel the need for expert evaluation & when their own vet told them the dog would not pass the OFA certification.

Many points are evaluated by 3 different expert vet radiologists when they access the X-ray. How well the hip joint fits into the socket, with careful measurements taken at each point. Formation of the bones. It is not just one thing that can make a dog dysplastic & fail to pass the certification process. Each defect is listed for the owner’s & for the vet who took the X-Rays when a dog is unable to certify. Hip problems can cause pain, crippling, the early onset of arthritis & complex surgical correction or euthanasia may result.

The dog’s X-ray is compared to other dogs of the same breed & age. If no evidence of hip dysplasia is recognized, the owner receives a certificate with the rating of the hip joint conformation as being Excellent, Good or Fair. A dog must be 24 months or older at the time of the X-ray to obtain an OFA hip certification. Preliminary evaluations are available on dogs younger than age 24 months when X-rayed, but no certification is given unless the X-Ray is done at 24 months or older, to be assured the bones have completed their growth. The owner & their vet will receive a Hip Concensus Report if the dog is inelegible for an OFA certification number & will list the reasons why.

It is prudent for breeders to submit ALL X-rays to OFA for their evaluation. That way the dogs who do not pass are included in the statistical basis & will give a more correct number of the incidence in the breed. There is no fee for submission & evaluation of affected dogs.

I find it interesting that other small breeds, with similar conformation & origination as the Tibetan Spaniel are being found to have many problems with hips. The Pug is currently 62.6% dysplastic - which is an improvement & DOWN 9.5% in incidence! The Shih Tzu is 19.00% dysplastic & UP 38.3%. With only 254 Tibetan Spaniel hip evaluations done Jan. 1974 through Dec. 2006, my concern is that we find this is a problem with higher incidence in the breed, as the Shih Tzu breeders have found it to be over the past few years.

Zen Tao began OFA evaluations on hips in 2001 & ALL dogs used for breeding have been X-rayed since that time.

PATELLA LUXATION

OFA maintains a patella luxation database for all breeds of dogs.

Any veterinarian may examine a dog, using the OFA specifications & their application that the owner submits to OFA, with the fee, for certification of Normal Results or for the classification of luxation & inclusion in the database for that breed. Patella luxation, commonly known as “slipped stifles” is a problem with the kneecap of the dog’s hind legs. It can cause dislocation, lameness & pain for the dog. Surgical correction may be required. As of Dec. 2006, only 28 Tibetan Spaniels applications for the patellar luxation database had been submitted. 17.9% of those were abnormal.

Zen Tao had examinations & applications for the OFA patellar luxation database on ALL Tibbies, aged 12 months to 15 1/2 years old, done between Nov. 2006 & through Jan. 2007. These will be submitted to OFA for certification & inclusion in the statistical database in the second quarter of 2007.

OTHER OFA certification & evaluations for cardiac Registry, Elbow Dysplasia & Thyroid have thus far shown no incidence or extremely low incidence of the Tibetan Spaniels submitted & do not currently appear to be problems in the breed. This could be subject to change as more are submitted.

LIVER FUNCTION PROBLEMS

ZEN TAO has had NO incidence of liver function problems in any Tibetan Spaniels & thus do not do the bile acid testing & screening for such problems. My Tibbies have lived to be 14 to 16 1/2 years old.

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