Multifocal Retinal Dysplasia

litter_screening Multifocal Retinal Dysplasia (MRD) in the Giant Schnauzer

Info

What is MRD?

Multifocal Retinal Dysplasia is an abnormal development of the retina, occurring when the two layers of the retina do not form together properly causing folds or round clumps (rosettes) to develop between them. The number of folds or rosettes can vary and may present as one or two small folds/rosettes, or they may be more numerous, but generally there is no noticeable effect on vision. The condition does not progress and often becomes less evident and may disappear with maturity.

Other more severe cases of MRD are seen in some breeds with areas of retinal detachment and haemorrhage that can cause impaired vision, however there have currently been no reported cases of such in the Giant Schnauzer.

Prevalence

On average 33% of litters eye screened in the UK between 2009-2015 contained puppies affected with MRD, ranging from 1 puppy in the litter to 6 out of 7 puppies in a litter.

BVA Litter Screen Statistics

Statistics recorded via the British Veterinary Association (BVA) on litter screens between 2009-2013 are shown below. The graph shows the number of litters screened for MRD for both affected and unaffected litters compared with the total number of litters registered. The number of litters containing affected puppies has decreased from 11 affected litters to 7 affected litters over the last 3 years. The graph also shows that in 2013 the number of litters tested is equal to the number of litters registered indicating that uptake of litter screening was excellent.

Age of Onset

MRD is congenital i.e. puppies are born with this condition and it is often detected at a puppy litter screen.

Mode of Inheritance

It is currently not known how MRD is inherited in the Giant Schnauzer, however it is thought to be a simple autosomal recessive gene which means that both parents of an affected puppy would have either one or two copies of the faulty gene. A minority of cases may be acquired during the puppy’s development, rather than inherited e.g. a viral infection during pregnancy.

Signs & Symptoms

In most instances there are no signs or symptoms, the eyes appear perfectly bright and clear, and usually there is no effect on vision.

Diagnosis

MRD is most often seen at a routine litter screen of the puppy’s eyes. Litter screening is a recommendation for breeders under the Kennel Club Assured Breeder Scheme. MRD may also be detected in older dogs, however there is a possibility that it may have improved or even disappeared with age. A list of eye examiners and their locations can be found on the following link:

Eye Panel List

The Animal Health Trust (AHT) also have eye testing facilities:
http://www.aht.org.uk/cms-display/sa_ophalmologybvaeye.html

Prognosis

Giant Schnauzers affected with MRD live a perfectly normal life and continue with their usual activities, sports, working etc. There is no treatment and generally it goes unnoticed.

Health Screening

Breeders are recommended to litter screen puppy’s eyes between the age of 5-12 weeks for MRD.

KC/BVA/ISDS Eye Scheme

For over 30 years the BVA has operated a hereditary eye disease screening programme in conjunction with the Kennel Club (KC) and the International Sheep Dog Society (ISDS). MRD is currently on Schedule B, under investigation within the scheme, which means it is recorded on the eye certificate but not published or recorded on Kennel Club health results database or on registration documents.

 

Where to go for an Eye Test/Litter Screen

Eye testing is carried out by specialist ophthalmology vets who are listed on the BVA panel of examiners.

Find an eye panellist online search

A full copy of the list can be found on the link below:

Eye Panel List July 2014

Alternatively the Animal Health Trust (AHT) also have eye testing facilities:
http://www.aht.org.uk/cms-display/sa_ophalmologybvaeye.html

Costs

Litter Screening (5 to 12 weeks) Excluding VAT(£) per dog Including VAT(£) per dog
1 to 3 puppies £25.83 £31 (per litter)
Per puppy for litters with more than 3 puppies £8.75 £10.50 (per puppy)
Adults – Routine Eye Examination Excluding VAT(£) per dog Including VAT(£) per dog
1st dog £43.33 £52
2 to 25 dogs £38.33 £46
25 dogs or more £30 £36
Examination of dogs over 8 years of age £25.83 £31

Requirements for an Adult Eye Test

1. Dogs should be permanently identifiable by microchip or tattoo, does not currently apply for puppy litter screens.
2. Registration documents are required on the day of the eye test for adult dogs.

Publication of Results

MRD is currently not a certifiable condition, it is on Schedule B, which means it is currently under investigation. therefore the results are not published in the Kennel Club Breed Records Supplement, on progeny registration certificates or on the Kennel Club health results database. The results of litter screens are not currently published.

Buyer Advice

Advice for Puppy Buyers

Ideally choose a breeder who has, or will undertake to litter screen their puppies for MRD before leaving the breeder.

Giant Schnauzer puppies should be eye tested before leaving the breeder, between the ages of 5-12 weeks, to determine if the puppy has been born with MRD. The breeder should be happy to talk to you about the litter screen and provide a copy of the official litter screening eye examination form. Puppies affected with a small number of MRD folds or rosettes, generally live a perfectly normal, happy and healthy life, usually with no noticeable effects. Retinal folds or rosettes generally do not progress, and in some cases may improve with age, or may totally disappear as the dog matures. However, if you are purchasing a puppy to breed from, you may want to discuss this and the litter screen, along with any other health tests, with the breeder.

Kennel Club Health Test Result Finder

Since MRD is not a certifiable condition the results are not published by the Kennel Club, it is only currently possible to see the eye result for Hereditary Cataracts. However the breeder should have a copy of the litter screen which will indicate if any of the puppies have MRD, a copy of the litter screen should also be included in the puppy information pack.

Breeder Advice

Advice for Breeders

Breeders are recommended to litter screen puppy’s eyes between the age of 5-12 weeks for MRD.

Find an eye panellist online search

The BVA litter screen statistics show that the incidence of MRD over the last 5 years is quite high, 31% of the litters that were screened contained affected puppies. Of the affected litters the number of affected puppies ranged between 9% – 100% of the litter.

In order to prevent MRD from escalating and potentially becoming more severe in the future, breeders have the opportunity to work towards reducing the incidence. One way this could be achieved is by litter screening at 5-12 weeks, before puppies leave the breeder, and selecting unaffected puppies for any future breeding. Also MRD may be reduced by removing affected dogs from a breeding programme if it is feasible without further restricting the gene pool.

There is a possibility affected puppies may later improve and MRD may not be detected in adulthood, this does not mean the gene(s) responsible for MRD have disappeared, they will still have the gene(s) and will still pass the defective gene onto their offspring. This is especially important since it has been suggested that breeding 2 affected dogs together may produce more severe lesions in the offspring.

The mode of inheritance for MRD has not been confirmed genetically, however it is strongly thought to be a simple autosomal recessive gene. Therefore both the parents that produced an affected puppy would either have one or two copies of the mutant gene.

The probabilities of producing affected puppies from a simple autosomal recessive inheritance are shown below (actual numerical values will vary)

recessive_inheritance

A ‘Clear‘ has 2 copies of the normal gene, is unaffected and cannot pass on a faulty gene.

A ‘Carrier‘ has 1 normal gene and 1 recessive abnormal gene, they are physically unaffected but may pass on the abnormal gene.

Affected‘ dogs have 2 copies of the defective gene of which they will pass on 1 of the affected genes to their offspring.

A mating that may produce affected puppies should never knowingly be carried out.

How You Can Help

Make a Donation to the GSHF

The purpose of the GSHF is to provide monies for research into inherited health problems in the Giant Schnauzer. All donations gratefully received.

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