EYE PROBLEMS IN THE TIPETAN TERRIER

SOME EYE PROBLEMS IN THE TIBETAN TERRIER

Cataracts in Tibetan Terriers are basically the same as in humans - the bluish white thickening that you can (eventually) see for yourself, though identifiable at a much earlier stage by a canine ophthalmologist. Some cataract development is normal, as part of the aging process. However, there is also a cataract which may occur in a much younger dog (as young as two or three or possibly earlier). These cataracts are considered hereditary. Whether to remove them or not is determined on a case-by-case basis as far as I know, with not removing them the more common practice as the dog doesn't usually benefit long-term.

Please click here for more indebt information on Cataracts, and also here for yet another article.

Lens Luxation is where the lens of the eye becomes detached. The way my ophthalmologist described it (for the dog) is it probably feels like a contact lens, which has become dislodged - extremely uncomfortable and painful. The "cure" is to remove the lens surgically in an operation that is not unlike cataract surgery though even more delicate. It also occurs bilaterally - meaning that when one lens goes, the other one will soon follow suit. The dog looses the ability to switch from "close up" to "long distance" vision - he'll be able to see things up close but not in the distance. Depending on where the lens fell to, there may also be a resultant secondary glaucoma - which requires eye drops daily for the rest of the dog's life. Lens Luxation is tricky - it does not occur before the age of three years (which is why in the past I did not breed my dogs before the age of three) and may occur as late as seven, eight, or nine year old, when a dog may have already produced/sired litters (which is one reason why I like people who buy my pups to keep in touch with me over the years). Lens Luxation is hereditary.

Please click here for more indebt information on Lens Luxation.

The major project that researchers were working on for many years was to find the "marker gene" - i.e. the piece of the DNA that gives the cells the "instructions" to grow in a particular way - for both PRA and Lens Luxation. Since the 2nd of November 2009 we have been able to take a DNA sample from a dog before it is bred and see if it carries the DNA "coding" to create Lens Luxation. We then can avoid breeding dogs who have these genes and therefore not produce pups with these defects (this is the ideal scenario), or at least avoid breeding two together that both have the piece of genetic coding to potentially match up so that the worst that we would produce would be potential carriers (then all the offspring would have to be tested as well for the next generation). While the ideal is to eliminate the problem, sometimes the "bad" gene can be tied to something desirable that you would loose along with the undesirable and sometimes there just aren't enough good quality dogs to select from if you eliminate all the carriers.

Below is the announcement that all genuine Tibetan Terrier enthusiasts were delighted to read.

PLL Testing

Congratulations to Dr Cathryn Mellersh & her team at the Animal Health Trust on successfully identifying the mutation for Primary Lens Luxation & for the development of a screening test. A DNA test to determine a dog’s genotype with respect to Primary Lens Luxation (PLL) is now available.

Testing kits can be requested by e-mail from swab.request@aht.org.uk.
If you do not have access to email you can telephone:
0044 (0)1638 555621 or fax 0044 (0) 1638 555666

When buying a Tibetan Terrier I strongly suggest buying from a breeder that can produce Certificates
for DNA screening of PLL and NCL, Certificates for the yearly BVA eye test, and also Certificate of Hip Score.

PLL Genetic Testing
02.11.2009

Joint statement by the Tibetan Terrier Association and The Tibetan Terrier Breeders & Owners Club regarding the genetic test for Primary Lens Luxation and it’s implication for breeding.

We strongly recommend that all breeding stock has a known genetic status for Primary Lens Luxation. This can be determined by a DNA test offered by the Animal Health Trust or as a consequence of knowing both parents are genetically clear.

The test can be obtained privately from the Animal Health Trust and taken to your vet where the permanent identification is then verified by their signature, or through clinics run by the Tibetan Terrier clubs.

Dogs which are carriers will not develop the condition. No tested carrier TT’s have yet gone on to develop PLL. It is essential that carriers are ONLY mated to genetically clear dogs. As the offspring have the potential to be carriers we advise that the litter be tested prior to sale, and wherever possible only the clears should be used in future breeding. It is hoped that no second generation carriers will be bred from. We recommend that the genetic status of any puppies sold is fully explained to new owners. Carrier puppies should be sold with breeding endorsement ‘Progeny Not Eligible For Registration’. This endorsement should be fully explained to potential owner and a signature of acceptance obtained.

PLL Testing Kits

Testing kits are now available from the Animal Health Trust.

Please contact either the Animal Heath Trust dnatesting@aht.org.uk
Or TTA Chairman Mrs. Pat Tempest ttachairman@aolcom

Animal Health Trust Link

Progressive Retinal Atrophy is where the retina of the eye gradually disintegrates. First the dog will lose his "night vision" and then it will progress to 24 hour blindness as well. This also is hereditary. There is no cure and no treatment. There seems to be two "varieties" of PRA - one that is evident by the time the dog is a couple of years old and one which is a very late onset (and might be missed by the average owner, or even vet, thinking the dog is just losing his/her vision due to old age). It is hereditary - so far as is known, both parents must be carriers (i.e., both may themselves appear to be fine but carry the genes which "pair up"). Researchers are still working on finding the DNA marker for this condition and until it is available we have to rely on are annual eye tests by a qualified Ophthalmologist

In the past and for many years, to facilitate breeders in Ireland, I was happy to organise an Eye Testing Clinic every year. This clinic was conducted by Dr. T. D. Grimes BVetMed PhD DVR DVOpthal DECVO MRCVS. I arranged for this clinic to be held at The National Show Centre in Cloghran, as it is considered by most to be an easy venue to reach, and is known to all but the novice breeders. I promoted the testing with a mailing shot well in advance of the date it was to be held, advertised it at shows and training centres, and also made it easy for some, by giving them the opportunity to book on line at this site. Now that I have moved to Wexford I can not offer this service at the moment, but I cannot stress strongly enough the IMPORTANCE OF ANNUAL EYES TESTS if you plan to breed.

Wednesday 8th May 2013

Progressive Retinal Atrophy (PRA) In Tibetan Terriers

Geneticists at the Kennel Club Genetics Centre at the Animal Health Trust have discovered a mutation that causes a form of progressive retinal atrophy (PRA) in Tibetan Terriers. We are calling this form of the disease PRA3 to distinguish it from other, genetically distinct, forms of PRA that are caused by different mutations, including the previously reported RCD4 mutation that is also known to cause PRA in some Tibetan Terriers. Together the PRA3 and RCD4 mutations account for approximately half of Tibetan Terrier PRA cases that we investigated during our research, although the number of samples from dogs with PRA was small and these proportions might not be representative of the wider population. During the latter half of 2013 the AHT will collaborate with the Kennel Club (KC) to screen a random subset of KC registered Tibetan Terriers to determine the frequency of both mutations more accurately. The mutation(s) that cause PRA in the other affected Tibetan Terriers remain(s) unknown and cannot therefore be detected by any DNA test at present.

As for RCD4, the PRA3 mutation is recessive, meaning a dog needs to inherit two copies of the mutation to be clinically affected with PRA. PRA3 is a late-onset condition and clinical signs can usually be detected by an ophthalmologist from 4-7 years of age. The onset of RCD4 is variable, but is usually around 10 years of age. Any Tibetan terrier that has 2 copies of either the PRA-3 or RCD4 mutation will develop PRA, assuming it lives long enough to do so.

A DNA test for PRA3 will become available from the Animal Health Trust July 8th 2013

Full details will be made available on our website shortly:

http://www.aht.org.uk/cms-display/genetics_tests.html

3rd May 2013

IMPORTANT ANNOUNCEMENT FROM ANIMAL HEALTH TRUST REGARDING PRA

from Cathryn Mellersh PhD
Head of Canine Genetics

New PRA DNA Test Available to Tibetan Terriers from 8th July, 2013

http://www.ahtdnatesting.co.uk

I am very pleased to be able to tell you that geneticists from the Kennel Club Genetics Centre at the Animal Health Trust have identified a mutation that causes progressive retinal atrophy (PRA) in the Tibetan Spaniel and Tibetan Terrier.

A DNA test based on this mutation will become available July 8th 2013.

The mutation was identified by Louise Downs, as part of her PhD studies, and represents the culmination of over a decade of investigation by Louise and other members of the research team into this condition.

There are many people I would like to thank for their contributions towards this success, including all the owners and ophthalmologists who have contributed DNA and information from their dogs & patients to the project and the PetPlan Charitable Trust, the Kennel Club Charitable Trust and all the Breed Clubs and individuals who have supported the research financially.

IMPORTANT ANNOUNCEMENT FROM ANIMAL HEALTH TRUST REGARDING PRA

PRA DNA Test Available to Tibetan Terriers

In 2011 geneticists working in the Kennel Club Genetics Centre at the Animal Health Trust identified a recessive mutation that is associated with the development of Late Onset Progressive Retinal Atrophy (LOPRA) in the Gordon Setter. Owners of Gordon Setters with LOPRA report that their affected dogs develop night blindness in the first instance, which is indicative of a rod-cone degeneration, so we termed this mutation rcd4 (for rod-cone degeneration 4) to distinguish it from other, previously described, forms of rod-cone degeneration.

Following our work in the Gordon Setter we have found the rcd4 mutation in PRA affected dogs of other breeds, including the Irish and English setter and now also the Tibetan terrier. As a result the AHT will make the rcd4 DNA test available to Tibetan terriers, from October 2nd, 2012. The DNA test we are offering examines the DNA from each dog being tested for the presence or absence of this precise mutation and is thus a ‘mutation-based test’ and not a ‘linkage-based test’.

Information about the rcd4 test, including details about how to order a test for your dog(s) are available here:

http://www.ahtdnatesting.co.uk

Other Forms of PRA in the Tibetan Terrier

We have tested DNA from 11 Tibetan terriers affected with PRA and found 2 of them were homozygous (carried two copies) for the rcd4 mutation. This indicates that there is at least one additional, genetically distinct, form of PRA segregating in the Tibetan terrier, that is caused by an as yet unidentified mutation and that this additional mutation(s) is probably more common than the rcd4 mutation. At the time of writing (September 2012) we are investigating the frequency of the rcd4 mutation in a random subset of Tibetan Terriers and expect to be able to update the Tibetan terrier community with the results by the end of October 2012. It is important for owners to appreciate that the rcd4 DNA test detects the rcd4 mutation only and cannot provide any information regarding the additional, currently unknown PRA mutation(s).