HEALTH OF THE BREED

Overview of health in the Parson Russell Terrier

The Parson Russell Terrier (PRT) remains a healthy breed, in part due to its recent, and in many cases, on-going role as a working dog. The healthy status of the PRT is acknowledged by the Kennel Club, with the breed being placed in Category One of the KC Breed Watch Scheme, indicating there are no current or emerging concerns regarding the health of the breed. 

The main focus of health in the PRT has recently centred around the diseases where DNA tests for disease causing genetic mutations are available.  While these DNA tests are vital in helping to improve health and ultimately eradicate disease within a breed, it is important to recognise that many factors affect the health of an individual or population from conception onwards.  Selection for breeding individuals must include more than just heath screening, however, with temperament, breed type characteristics and genetic diversity requiring consideration.  We all want our dogs to live happy and healthy lives and regardless of breed, health starts with the selection of good breeding stock followed by appropriate nutrition, exercise, preventative and appropriate veterinary treatment and meeting behavioural needs. 

DNA testing in the Parson Russell Terrier

In recent years the breed has seen the introduction of DNA testing for single gene mutations.  Genetic diseases which can be currently tested for in the Parson Russell Terrier are Primary Lens Luxation (PLL), Late Onset Ataxia (LOA), Spinocerebellar Ataxia (SCA) and most recently Urate Stones (Canine Hyperuricosuria / HUU).  The advantage of these DNA tests is that they are performed once in a dog’s lifetime, or after three or four generations of breeding from clear dogs.  A summary of the key features surrounding these diseases and interpretation of DNA results is outlined below.

The four tests are currently offered by the Animal Health Trust and are available to purchase from dnatesting@aht.org.uk  

Prices vary depending on the disease being tested (PLL -£35; LOA - £40; SCA - £40 and HUU - £40).  Discounts are occasionally available via the breed club and an additional discount of 30% has been offered for KC Assured Breeders Scheme members. 

What does DNA testing my dog involve?

Puppies can be DNA tested from at least four weeks of age and must be weaned to prevent contamination of the sample with the mother’s DNA.  A cheek swab is used to collect cells for DNA analysis.  Only swabs issued by the Animal Health Trust (or equivalent test issuing institute)  may be used, and are issued once the tests have been purchased via the webshop (www.ahtdnatesting.co.uk).  You may choose to have the results delivered either by email (quickest) or post. Most results are received within 3 to 6 working days.  The Parson Russell Terrier Club requires all samples to be taken by a veterinary surgeon.

Embryonic Stem Cells

WHAT DNA TESTS ARE CURRENTLY AVAILABLE IN THE PRT?

Primary Lens Luxation (PLL)

In affected dogs the fibres supporting the lens breakdown or disintegrate, causing the lens to fall into the wrong position within the eye. If the lens falls into the anterior chamber of the eye, glaucoma and loss of vision can quickly result, accompanied by pain.  Lens luxation may also arise from trauma and as yet, unidentified genetic mutations.

Late Onset Ataxia (LOA)

Affected dogs begin showing signs of cerebellar ataxia (loss of muscle coordination leading to an altered gait and loss of balance) between 6 and 1 year of age. The coordination difficulties become more severe and the affected dogs are often euthanized by 2 years of age due to poor quality of life.

Spinocerebellar Ataxia (SCA)

Affected dogs show progressive signs of cerebellar ataxia (loss of muscle coordination) as early as 2-6 months of age. The majority of cases also develop myokymia (involuntary twitching of the muscles) which also becomes progressively worse with age. A small percentage of dogs with SCA have true epileptic seizures, some as young as 10 weeks of age. Most dogs with SCA are euthanized young due to poor quality of life.

OTHER THINGS TO CONSIDER

OTHER FORMS OF ATAXIA IN THE PRT

Another form of hereditary ataxia called Neonatal Granuloprival Ataxia (NGA) has been recognised, though the genetic mutation still needs to be identified.  Unlike SCA and LOA, difficulties co-ordinating and walking are present from the time they begin to walk.  NGA is the result of degeneration of the granular layer of the cerebellum. 

The Animal Health Trust and the University of Missouri have found a small number of dogs exhibiting cerebellar ataxia, with onset starting after weaning.  It is suggested that this may be another hereditary form of ataxia or may be an acquired cause. 

URATE STONES (CANINE HYPERURICOSURIA - HUU)

A genetic mutation common to many breeds, DNA testing for Urate Stones is a newly available test and is currently viewed as a precautionary until the prevalence of Urate Stones in Parson Russell Terriers is established.  Currently no Parson Russell Terriers have been tested, beyond those used in the initial research programme.  Affected dogs excrete uric acid, leading to the formation of urinary calculi (stones), which many then necessitate surgery.  Dogs from susceptible breeds that experience problems urinating freely should be referred for veterinary advice immediately.

WHAT DOES IT MEAN IF MY DOG IS A HEREDITARY CLEAR, CARRIER OR AFFECTED?

KC registration papers may show the hereditary status of a dog.  This status is based on the mode of inheritance for the disease, as a result of known status in both parents.  It is not necessary to DNA test this dog to determine its DNA status for a particular disease.  It is however recommended that hereditary clears are DNA tested every three or four generations of breeding from clears.

SOURCES OF FURTHER INTEREST

Some further sources of information

The Animal Health Trust provides reliable sources of information on DNA genetic testing.

The Kennel Club website provides a wealth of information on dog health in general and specific to breeds.

Within the Kennel Club main site there is a health area where tools useful to breeders and pet owners can be found, most notably Mate Select and the Health Tests Results Finder.

MATE SELECT

This enables the inbreeding coefficient (indicating relatedness) of individuals and potential matings to be calculated and provides the average inbreeding coefficient of the breed to be looked up.  Mate Select is therefore a useful tool for managing the genetic diversity of a breed in order to minimise the risk of future genetic problems arising.

HEALTH TESTS RESULTS FINDER

As part of the Mate Select service offered on the KC website, the Health Tests Results Finder allows you to search for health results for any dog registered on the Kennel Club’s Breed Register.  Results from a BVA/KC health scheme and official KC DNA testing schemes are available.

Information provided by Dr Sarah Broadberry – Kennel Club Breed Health Representative

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