In terms of health issues with Leos, they are by and large, a very healthy breed compared to others, but that said, they are some health issues associated with them. Cancers are an issue for the breed and in particular bone cancers. Hip Dysplasia is also an issue due to their size. Other health issues include Inherited Leonberger Polyneuropathy (ILPN), Laryngeal Paralysis (LP), Dilated Cardiomyopathy (DCM), and Anal Furunculosis (AF).
The condition known as Inherited Leonberger Polyneuropathy (ILPN) is currently being researched in both the US and in Switzerland. To date, a genetic marker for one type of ILPN has been identified (which is called ILPN1) and many the Leo community worldwide have and continue to contribute to this study. The original study, conducted by Dr. Diane Shelton, attempted to see if there was a connection between ILPN in dogs to a similar condition found in humans called Charcot-Marie-Tooth Disease. Both conditions are characterised by peripheral muscle and nerve wasting which is accompanied by loss of sensitivity in the extremities of the body. Dr. Diane Shelton defined the breed specific version of ILPN in 2003; however there is evidence of the disease within the breed back as far as the 1950’s, where academic papers describe a condition of gait abnormalities in Leo’s.
Description of the Condition
A Polyneuropathy is a disease which affects more than one nerve in the dog’s body. Inherited Leonberger Polyneuropathy affects the longest nerves of the body called peripheral nerves. This causes weakness and dysfunction in the muscles that the particular nerve path serves. It can also cause a noticeable shake/wobble to occur in the dogs back end. It can also occur in the dogs’ front end too. ILPN is a progressive (i.e. it gets worse as time goes on) and is often very debilitating and if the larynx (Laryngeal paralysis) is involved it can be fatal. It is a condition in which the nerves furthest away from the spine are affected first and as it is progressive more nerves become affected over time.
Countries with a tight genetic basis (Line-breeding / inbreeding) are known to produce more cases of ILPN (Leonberger Union Website 2009). The age on onset can be as young as a few months of age up to as late as over 8 years of age.
What to look for?
The onset of this condition is slow and can often be missed until the signs and symptoms are severe. The most common symptom is gait abnormalities and/or weakness in the rear limbs. Often subtle, it may show simply as shortened strides being taken by the dog on one side or a slight dragging/wearing of the toenails. Some people have described it as the dog takes a split second more to put his/her foot on the ground, like their movement is off a beat. The progression of this disease can be slow and gradual or it can be rapid. Due to the nerve being affected, lack of feeling and weakness is secondary to the nerved degeneration and may present as misplacement of the feet and stumbling, wobbling, crossing of the limbs, exaggerated and lengthened strides or sometimes a high stepping walk (which is called marionette-like walking or like a bicycle like action while walking). Eventually, as the nerves die back, the muscles will waste away and be inactive and this can lead to paraplegia (loss of use of the hind legs) and tetraplegia (loss of use of all four legs). Another symptom is exercise intolerance or reduced exercise tolerance.
Types of ILPN
At present the researchers are indicating that there are definitely two types and possible a third. The first type is ILPN1, which is characterised by clinical symptoms being present before the age of 3 and according to the data from Berne, dogs that are tested as affected (D/D) (having two copies of the affected gene) will go on to develop early-onset and sever form of ILPN. Matings that could produce D/D puppies are not allowed in Ireland.
The second type is ILPN2 and the researchers have been working on this for about a year to aim to identify the gene(s) that are involved. To date, they have made some progress towards identifying a genetic marker for late onset polyneuropathy, but final identification of this mutation or mutations still remains somewhat elusive. The symptoms of late onset ILPN are less severe than that of ILPN1.
In more recent times, the researchers believe that there is at least one additional locus for ILPN (which will become ILPN3). Research is ongoing in this area.
Diagnosis
Confirmation of a diagnosis may need to be carried out by a specialist in neurology. A more definite diagnosis can be made by biopsy of the cranial tibial muscle and the peroneal nerve which is done post mortem.
Research into ILPN
In June of 2010, the first marker test for the particularly debilitating form of early onset form of ILPN was released. This test has been able to identify the mutation responsible for the one form of the condition that has been designated as ILPN1 (known as early onset). Sadly, this is not the only form of the condition and the researchers are working furiously to progress to unlock the mutation(s) for all forms of polyneuropathy in the breed. In essence, a Leo can have a clear result of the ILPN1 mutation (N/N) having two copies of the normal gene, but may still suffer from another form of the illness.
Genetic testing began in earnest, through blood sampling of dogs, after June 2010 and from the 3935 dogs tested about 15% have a positive test for being at risk (D/N – also known as carriers) as of these they have concluded that it would appear that perhaps as many as 50% of D/N carrier cases will themselves show symptoms of polyneuropathy by mid-life, regardless of the fact that they carry only one copy of the mutation. A much smaller percentage were deemed to be affected D/D.
In September 2011, the University of Minnesota provided an update about recent advances in their research into Leonberger Polyneuropathy. There have been 48 Leos showing strong indications of ILPN despite having a clear ILPN1 result and a detailed study of DNA gathered from these dogs will hopefully provide the much needed key to finding the markers for further forms of the condition.
The ultimate goal of developing one or more genetic marker tests for the defective gene or genes is to eliminate the condition from the breed in over few generations. It is imperative that all breeders in Ireland contribute to this research and get all their breeding dogs tested.
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