Multifocal Retinal Dysplasia (MRD) in the Giant Schnauzer
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. Irregularly shaped (geographic) areas of retinal dysplasia may also be encountered, although less common in the breed. In most cases, the lesions are frequently seen in the tapetal fundus dorsal to the optic disc. Litter screening is useful, although subtle changes are not always clearly defined, and unlike retinal folds/rosettes the geographic form does not appear to improve with maturity. Another more severe case of retinal dysplasia is seen in some breeds with total retinal detachment and haemorrhage causing loss of vision, however there have currently been no reported cases of such in the Giant Schnauzer. There is currently only data from litters between 2009 – 2017 On average 29% of litters eye screened in the UK between 2009-2017 contained puppies affected with MRD, ranging from 1 puppy in a litter to all puppies in a litter. MRD is congenital i.e. puppies are born with this condition and it is often detected at a puppy litter screen. 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. In most instances there are no signs or symptoms, the eyes appear perfectly bright and clear, and usually there is no apparent effect on vision. 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: Find an eye panellist online search 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. 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 monitored via the BVA. 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 Costs Up-to-date information on the current cost of eye testing can be found on BVA cost of submissions and examinations which includes a full breakdown of reduced fees for older dogs and group examinations. Requirements for an Adult Eye Test Publication of Results MRD is currently not a certifiable condition in the breed, which means it is being monitored by the BVA. Advice for Puppy Buyers Ideally choose a breeder where both the sire and dam have been eye tested within the last 12 months, and who has or will undertake to litter screen their puppies eyes 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 or any other congenital eye defects. 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 Adult eye results are only published for the condition: hereditary cataracts, via the Kennel Club health test results finder. Any other conditions are listed as ‘Results with owner” or “Observation made refer to owner”. It does not include results from puppies tested during a litter screen, talk to the breeder and ask to see copies of sire/dam eye test and puppy’s litter screen, which will identify if any of the puppies are found to have MRD or any other congenital eye condition. A copy of the litter screen should be included in the puppy information pack. 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 has been quite high, between 40-45% of litters screened have contained affected puppies. Of the litters containing affected puppies the number of affecteds 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, where possible, for any future breeding. 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) 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. The purpose of the GSHF is to provide monies for research into inherited health problems in the Giant Schnauzer. All donations gratefully received.
What is MRD?
Prevalence
Age of Onset
Mode of Inheritance
Signs & Symptoms
Diagnosis
Prognosis
2. Registration documents are required on the day of the eye test for adult dogs.
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