Genetic Testing
Why Test Your Jack Russell Terrier?
If you are a breeder, prospective dog owner or someone looking for a highly trained dog for specific service work, hunting or the show ring, understanding your Jack Russell Terrier's genetic health will help you make better decisions concerning your dog. It is always best to test a dog before it is bred so that you are aware of any potential genetic disorders that it could pass to its offspring.
DNA tests for specific diseases remain the "gold standard" in determining an animal's genotype, but in the absence of available DNA tests, phenotypic evaluations are the best alternative. Information regarding the test results from the sire and dam, along with information on other close relatives such as siblings, half-siblings, aunts and uncles allows breeders to apply greater selective pressure to produce normal offspring and avoid affected offspring.
Source: Orthopedic Foundation for Animals
Primary Lens Luxation (PLL) - Vision
The lens of the eye normally lies immediately behind the iris and the pupil, and is suspended in place by a series of fibers, called zonular ligaments. It functions to focus light rays on the retina, in the back of the eye. When partial or complete breakdown of the zonular ligaments occurs, the lens may become partially dislocated (Lens Subluxation) or fully dislocated (Lens Luxation) from the lens' normal position. Lens Luxation can lead to inflammation (Uveitis) and Glaucoma (increased intraocular pressure). This can result in painful, teary, red eyes that may look hazy or cloudy. Both Uveitis and Glaucoma are painful and potentially blinding diseases if not identified and treated early. PLL testing requires a DNA sample.
Source: Canine Lens Luxation Basics
Spinocerebellar Ataxia (SCA) - Neurologic
The cerebellum is the part of the brain responsible for coordinating movements. Ataxia comes from a Greek term meaning "without order". When the cerebellum cannot coordinate movement, the dog can move, but the movement is poorly coordinated. They are not weak, in fact, often the movements a dog with ataxia makes are too strong. They have a goose-stepping gait and when excited or running, their legs may appear to be going every which-way. Sometimes they have problems with their balance and will fall frequently. SCA testing requires a DNA sample.
Source: College of Veterinary Medicine - University of Missouri-Columbia
Canine Degenerative Myelopathy (DM) - Neurologic
Degenerative myelopathy (DM) is a progressive disease of the spinal cord in older dogs. It begins with a loss of coordination (ataxia) in the hind limbs. The affected dog will wobble when walking, knuckle over or drag the feet. This can first occur in one hind limb and then affect the other. As the disease progresses, the limbs become weak and the dog begins to buckle and has difficulty standing. The weakness gets progressively worse until the dog is unable to walk. Tests results are: Normal, Carrier and At Risk. DM testing requires a DNA sample.
Canine Eye Registry Foundation (CERF) - Vision
The Canine Eye Registration Foundation was formed by breeders that were concerned about heritable eye diseases. The foundation worked with veterinary ophthalmologists to devise a yearly evaluation of breeding dogs, known as a CERF exam. The phenotypic appearance of each eye is evaluated during the exam and this does not imply that an ocular disorder will not subsequently develop. Therefore, dogs with phenotypically healthy eyes are cleared for one year of breeding, but there is no genotypic clearance. Breeding dogs may show phenotypic characteristics of an ocular disorder during a future CERF exam. CERF testing requires a physical exam. The major goal of a CERF exam is to stop breeding any dogs that display potentially blinding diseases including microphthalmia, cataracts, colobomas, progressive retinal atrophy, and retinal dysplasia. Breeding and potentially-breeding dogs are typically subject to a yearly CERF exam as the dog ages from about 4 months to 9 years.
Source: Orthopedic Foundation for Animals
OFA Eye Certification Registry (CAER) - Vision
The purpose of the OFA Eye Certification Registry (CAER) is to provide breeders with information regarding canine eye diseases so that they may make informed breeding decisions in an effort to produce healthier dogs. CAER certifications will be performed by board certified (ACVO) veterinary ophthalmologists.
Source: Orthopedic Foundation for Animals
Brainstem Auditory Evoked Response (BAER) - Hearing
The hearing test known as the brainstem auditory evoked response (BAER) or brainstem auditory evoked potential (BAEP) detects electrical activity in the cochlea and auditory pathways in the brain in much the same way that an antenna detects radio or TV signals or an EKG detects electrical activity of the heart. The response from an ear that is deaf is an essentially flat line. Each ear is tested individually, and the test usually is complete in 10-15 minutes. BAER testing requires a physical exam and a hearing test.
Hyperuricosuria (HU) - Kidney
Hyperuricosuria (HUU) means elevated levels of uric acid in the urine. This trait predisposes dogs to form stones in their bladders or sometimes kidneys. These stones often must be removed surgically and can be difficult to treat. HUU is inherited as a simple autosomal recessive defect. A mutation in exon 5 of the gene Solute carrier family 2, member 9 (SLC2A9) has been found to be associated with hyperuricosuria in dogs. HUU can occur in any breed but is most commonly found in the Dalmatian, Bulldog and Black Russian Terrier.
A DNA test for the SLC2A9 mutation can determine the genetic status of dogs for HUU. Dogs that carry two copies of the mutation will be affected and susceptible to develop bladder/kidney stones. The SCL2A9 mutation is not the sole cause of urate bladder stones in dogs. Other factors such as liver disease and diet need also be considered in clinical evaluation.
We recommend testing any dog that has formed kidney or bladder stones composed of urate or uric acid. If the dog has the mutation then treatment modalities for Dalmatians can be used to treat the dog
Late Onset Ataxia (LOA) - Neurologic
Spino-cerebellar Ataxia can start showing signs as early as 12 weeks, but in most cases symptoms occur between 6-9 months. Some may move well in a straight line, but stumble or fall when making fast turns, climbing stairs, or attempting to catch a ball. You will see signs of a staggered gait, lack of balance, rolling when running, and eventually the onset of seizures. The reported SCA cases the RF have been involved with, all have myokymia seizures, it is these uncontrollable seizures that deteriorate the quality of life and death is certain.
While there is a test available for Late On-set Ataxia we have never seen LOA in the JRT. Researchers at the University of Missouri and Animal Health Trust did not find the LOA gene mutation in the Jack Russell Terrier. While some breeders have decided to test for LOA, all have tested Normal and those are included in the Health Registry.
Neonatal Ataxia (NNA) - Neurologic
Neonatal Ataxia is a progressive, neonatal onset, cerebellar ataxia described in Jack Russell Terriers. Similar to other ataxias, clinical signs consist of intention tremors, loss of coordination, and inability to stand and move in a forward direction.
Neonatal Ataxia is seen as early as two weeks of age. Pups get separated easily from the litter, they struggle with an uncontrolled head motion in an effort to achieve forward motion to return to the litter.
If they survive until four weeks of age they master standing with a very wide stance and have a drunken, staggering gait, with frequently having a goose stepping movement of the front limbs. When eating they peck their food, raising their head quickly to avoid tumbling forward. They spend most of their time and energy trying to upright themselves after falling. While they have a desire to run and play they are unable to do so. Most pups are euthanized soon after diagnosis due to the lack of quality of life. Breeders who have experienced this horrific disease will tell you how sad it is to witness a puppy with the terrier drive and determination fail at trying to be normal.