UK club meeting on SM/MVD research and breeding

NOTES ON THE MEETING HELD AT THE ANIMAL HEALTH TRUST, 25th JULY 2008

Present:
Sarah Blott ((Research Group Leader, Quantitative Geneticist, AHT)
Luisa de Risio (Head of Neurology, AHT)
Ruth Dennis (Head of Diagnostic Imaging, AHT)
Cathryn Mellersh (Research Group Leader, Head of Canine Genetics, AHT)
Tom Lewis (Quantitative Geneticist, AHT)
Jeff Sampson (The Kennel Club)
Clare Rusbridge (Neurologist, Stone Lion Veterinary Centre)
Penny Knowler (Researcher)
Mrs V Hull (Chairman, Southern CKCS Club)
Mr R Cornaby (Vice-Chairman, Midland CKCS Club)
Mr D Crossley (Chairman, Humberside CKCS Club)
Mrs L Jupp (Chairman, CKCS Club)


The meeting was sponsored by The Kennel Club and Chaired by Dr J Sampson.


The purpose of the meeting was to discuss data collection for Syringomyelia, genetic evaluation, collection of other health information, eg. MVD.
The following matters were discussed and/or noted:
MRI Scan results:

It was agreed that there is a need to standardise MRI scan results before certification.

To facilitate this, The Kennel Club will organise a meeting of neurologists and radiologist to agree a protocol. It was proposed that a panel should be formed, consisting of a minimum of five neurologists and radiologists, any two of which will be required to agree SM/CM status. It was noted that this system already works well for hip and elbow scoring. An appeal system will be set up to deal with any disputes. Scan results could be assessed by the panellists using a computer link, and therefore they would not have to be based at the same centre. Eventually MRI images will be sent directly to the panel by clinics where the MRI scan has been done.

In the interim, while the panel and protocol are being set up, MRI scan certificates received by dog owners from individual clinics can be sent directly to the AHT. This will need the support of all clubs, to encourage members to send results of MRI scans direct to the AHT, where confidentiality has been assured.

The scheme will not initially be adopted by the KC/BVA but the aim is that the scheme should be developed as a Breed Club scheme and should eventually be adopted by the KC/BVA.

It was suggested that the minimum age for an MRI scan should be 12 months. Dogs scanned under 12 months old will be given an interim report.

KC Heart Testing Scheme:

The BVA/KC are currently considering the introduction of a heart testing scheme for 4 breeds of dogs, including the Cavalier. A meeting will be held on 15th September.

If the scheme is adopted, results will be published in the quarterly Breed Registration Supplement and will appear on the progeny’s registration certificate.

Additionally, the KC is looking at ways by which breeders could access health results of dogs/ bloodlines. This service will be available to breeders and pet owners.

Permanent Identification:

The Kennel Club is currently unwilling to introduce mandatory dog identification.

However, if the clubs set up their own health scheme that includes the need for identification, it is likely that this element would be maintained if the health scheme were later adopted by the KC/BVA.

It was agreed by breed representatives present that clubs would encourage the permanent identification of dogs by microchip or swab, to ensure that data collected for Sarah Blott is valid, and thus help research teams to evaluate hereditary factors correctly. This will assist EBV estimation in a positive and decisive way.

The cost of micro chipping would be approximately £25. Cheek swabs would be £5 and kits are available from the Animal Health Trust.

Club representatives present, considered that these alternative methods could be made available at club shows and events. Dr Samson advised that dispensation could be obtained from the Kennel Club to allow un-entered dogs into such events, to take part in the scheme.

DNA profiling currently costs approximately £65. The Animal Health Trust is currently looking for ways by which this cost can be reduced.

It was noted that microchips should be positioned well down the neck, to avoid affecting MRI scan.

Estimated Breeding Values (EBVs)

It was agreed that all scan results should be sent direct to Sarah Blott for her continuing research. It was noted that a consent form will be needed to allow results to be used for research, and this can be based on current forms used for hips and elbow examination. The format of the form will be agreed by the panel of neurologists and radiologists.

It was noted that first estimates of breeding values are now available for every cavalier in the UK.

There was discussion on when EBVs should be made available to breeders. It was suggested that should EBVs become available too soon, when the programme is still at a very early stage, results could be disappointing and may alienate breeders. It was agreed that more information (ie. further MVD and MRI results) should be obtained before the system is introduced, so that it is more reliable and thus more beneficial.

It was noted that dogs do not have to be scanned to be given a breeding value. There are various ways in which EBVs could be presented to breeders. The AHT will work with the Breed Clubs over the coming months to determine the best way of doing this. The breeding value of each dog will change over the years, as information is obtained on its progeny.

It was noted that Sarah Blott particularly requires information on clear dogs.

This will be a web-based scheme but available in print from AHT, to any breeder on request.

Sarah Blott agreed to produce a special leaflet for distribution to club members, explaining the scheme in layman’s terms.

The AHT data collection will be used to provide breeders with EBVs for safer breeding programmes to reduce the incidence of both MVD and SM, and could include any other condition as appropriate in the future. The EBV system will become even more reliable when permanent identification (PI) is introduced throughout all members’ breeding stock.

CKCSC Hearts database:

The Cavalier Club hearts research database, which is currently being managed by Liverpool University, is to be made available to AHT. This will provide further data information. It should be noted that the strict confidentiality of the database would be maintained by AHT.

KC Information leaflet:

The Kennel Club would be willing to include leaflets with registration documents, informing owners of health issues and screening programmes within the breed, but this needs to be agreed by all breed clubs.

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It was agreed that more information (ie. further MVD and MRI results) should be obtained before the system is introduced, so that it is more reliable and thus more beneficial.

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Karlin said:

As the notes make clear, Sarah Blott feels there isn't enough information yet for the EVBs that do exist to be released for breeder use.

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Syringomyelia is believed to be a complex disease, where the disease phenotype results from the effects of several genes plus environmental influences. The phenotype includes not only the affectation status of the individual but also clinical observations and measurements made from MRI scans. In order to determine the genetic basis of the disease two different approaches are being taken. The first uses a population-based approach, where phenotypic measurements and pedigree information are used to estimate the heritability of the disease. This requires that we have accurate phenotypic measurements, including MRI scans, on as much of the population as possible, together with pedigrees so that genetic relationships between individuals can be identified. Where information exists on other diseases, such as Mitral Valve Disease, this can also be included in the analysis allowing genetic correlations between diseases to be established. It is important to know about correlations, or relationships, between diseases so that any selection strategies take account of the possible influence that selection against one disease may have on other diseases. The second approach to understanding the genetic basis of a disease is to use molecular genetics and gene mapping techniques to try to identify the underlying causative mutations. This approach is also being used to try to identify genes causing both Syringomyelia (SM) and Chiari Malformation (CM) in the Cavalier King Charles Spaniel (CKCS) and other toy breeds such as the Brussels Griffon. It is hoped that this will identify regions of the genome harbouring the genes causing these conditions.

Data collected by Penny Knowler and Clare Rusbridge is currently being used as the basis for the population-based analysis of heritability. Their database contains clinical observations for SM and CM on around 1,400 dogs and MRI scan results for around 700 of these dogs. We have also been given access to the full UK Kennel Club pedigree records for CKCS. This enables us to estimate the heritability of SM and the genetic correlations between SM and measurements made from the MRI scans. The information obtained from this analysis then allows us to derive estimated breeding values (EBVs) for all measured dogs as well as all dogs in the pedigree. Once the results of the gene mapping studies become available it is hoped to bring this information together with the population analysis to facilitate the calculation of genomic breeding values (geBVs).

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Early estimates of the heritability of SM suggest it is around 0.7-0.8* or that 70-80% of the variation between individuals is genetic in origin and about 20-30% is environmental. In the case of SM not much is known about the environmental influences and these may include in-utero or developmental effects. The heritability is sufficiently high, however, that genetic selection against the disease should be very successful. Heritabilities for Chiari Malformation, Cerebellar Herniation and Medullary Kinking are also very high. Genetic correlations between these traits and SM are positive and, interestingly, less than one. This suggests that different genes may be controlling SM and CM and that it will be possible to select against SM even if dogs have the malformation (CM).

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