Centronuclear Myopathie in Labrador Retrievers
In light of recent events, the breeding committee Labrador wishes to present new facts about the problem of myopathy and its various forms in Labrador Retrievers in order to prevent further confusion among interested breeders and dog owners..
The first cases to be classified as myopathy in dogs bred within the German Retriever Club (DRC) stem from 1998. During the first weeks three pups from one litter seemed to develop quite normally, but after having moved to their new homes, they became fastidious about food. Muscle development was retarded, especially in the foreparts of the body (neck, breast and front legs). They were unable to walk normally, but moved with an awkward gait similar to that of a hare, accompanied by nodding movements of the head and with a crooked back (see video of an affected 5 month old American Labrador). Two of those pups had to be put down to spare them further suffering
It was already known then that myopathy is a hereditary disease in Labradors; additional cases occurred in other European countries (Switzerland, France, UK and – later on –Sweden) as well as in the USA and Canada.
Scientific research in this field has proceeded and in 2005 a group at Ecole Nationale Vétérinaire d'Alfort in France succeeded in developing a DNA test which allows identification of dogs that can transmit this form of myopathy (CNM). It is now possible to prevent the occurrence of this disease by testing to show that at least one parent of a planned litter does not transmit it – See the box below for more information on CNM inheritance patterns.
CNM is – as in prcd-PRA -a simple recessive trait; this means that both parents must be carriers and transmit the deleterious gene to produce affected offspring
A carrier mated to another carrier will produce - statistically – 25% affected, 50% carriers and 25% unaffected offspring. Therefore a dog tested free of the gene can never produce any affected offspring
What was causing some confusion, is the fact that only the form of myopathy described above (CNM) can be detected with this DNA test. This particular form has been referred to as:
- HMLR (= Hereditary Myopathy of the Labrador-Retriever),
- ARMD (= Autosomal Recessive Myopathy),
- Type II deficiency Myopathy oder
- Labrador Muscular Myopathy
Other forms and diseases which have also been referred to as myopathies (the medical term for “Muscle diseases”) cannot be detected by the CNM test. These include::
- Dystrophic Myopathies of other breeds
- Cardiomyopathy, a disease affecting the heart muscle
CNM is a very grave disease in young Labradors, resulting also in traumatic experiencesfor dog owners and breeders. Therefore, whenever possible DNA testing of stud dogs and dams should be performed and breeding undertaken only in accordance with the results obtained.
In particular, the test results of Swedish breeders, who are truthful about their carrier results (dogs appear healthy, but are able to transmit CNM to their offspring), showed thatthis disease is much more widespread than we ever expected – see test results on the homepage of Labrador Retrieverklubben, Sweden (= "Testade hundar som är anlagsbärare").
It is easy to avoid further cases of CNM – we need only take advantage of our new opportunities
Submission for the CNM test
© Dr. Andrea Florschütz, Bilder: Hans-Georg Keimer
We thank Dr. Bruce Boschek for his help with the English translation.