Parson Russell Terrier Health
Happy Healthy TerriersResponsible breeders do everything they can to make sure they are producing happy healthy puppies. All Posey Canyon dogs used for breeding have had all the health tests that are recommend for our breed. These test include BAER (hearing), OFA Patellas, annual CERF (vision) testing and PLL if the parents are not proven PLL clear. Our results are entered into the CHIC (Canine Health Information Center) database and the OFA database.
On this page you will find information and resources regarding these tests.
This is a centralized canine health database jointly sponsored by the AKC/Canine Health Foundation (CHF) and The Orthopedic Foundation for Animals (OFA). In time, it will provide a reliable source of information regarding dogs in our breeding programs. Also provide an opportunity to analyze pedigrees of proposed breeding from a health/genetic viewpoint in addition to traditional methods of selection.
All dogs that are to be included in this program must be permanently identified in the form of a microchip or tattoo. Parson Russell Terriers must have been BAER (hearing) tested, CERF (vision) tested and OFA patella checked to receive a CHIC number.
The CHIC website is located at www.caninehealthinfo.org.
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 waveform consists of a series of peaks numbered with Roman numerals: peak I is produced by the cochlea and later peaks are produced within the brain. The response from an ear that is deaf is an essentially flat line. In the sample recordings below puppy 1 heard in both ears, Puppy 2 was deaf in the left ear, Puppy 3 was deaf in the right ear, and Puppy 4 was deaf in both ears. Because the response amplitude is so small it is necessary to average the responses to multiple stimuli (clicks) to unmask them from the other unrelated electrical activity that is also present on the scalp (EEG, muscle activity, etc).
The response is collected with a special computer through extremely small electrodes placed under the skin of the scalp: one in front of each ear, one at the top of the head, and one between and behind the eyes. It is rare for a dog to show any evidence of pain from the placement of the electrodes - if anything the dog objects to the gentle restraint and the irritation of wires hanging in front of its face. The stimulus click produced by the computer is directed into the ear with a foam insert earphone. Each ear is tested individually, and the test usually is complete in 10-15 minutes. Sedation or anesthesia are usually not necessary unless the dog becomes extremely agitated, which can usually be avoided with patient and gentle handling. A printout of the test results, showing the actual recorded waveform, is provided at the end of the procedure. Test results are confidential, but anonymous details will be used in Dr. Strain's ongoing deafness research for later publication and education of veterinary practitioners.
Dr. George M. Strain
Louisiana State University
Comparative Biomedical Sciences
School of Veterinary Medicine
Baton Rouge, Louisiana 70803
Posey Canyon Parson Russell Terriers used for breeding are all BAER tested normal. This test is a one time test.
CERF was founded by a group of concerned purebred owner/breeders with a goal of eliminating heritable eye diseases in purebred dogs through registration, research, and education. CERF is dedicated to educating the public on matters involving canine eye disease. It provides a variety of reports to help educate owner/breeder on heritable eye disease questions, healthy breeding stock, and breed-specific eye problems.
The Genetics Committee of the American College of Veterinary Ophthalmologists lists Lens Luxation and Cataracts in its Occular Disorders Presumed to be Inherited in Purebred Dogs for the Parson Russell Terrier.
Occurrence of a defect can not be anticipated in a given terrier, and the age of onset of the disorder(s) varies from quite early (less than one year of age) to several years of age. The JRTCA Breeder's Committee is urging terrier owners to have their Jack Russell's CERF tested yearly. Don't be fooled into waiting for a symptom of an eye problem. Many times there are none. Early detection and reporting is important to the future of the Jack Russell Terrier.
Posey Canyon breeding dogs up to eight years of age are CERF tested annually by a certified Veterinary Ophthalmologist.
The patella, or kneecap, is part of the stifle joint (knee). In patellar luxation, the kneecap luxates, or pops out of place, either in a medial or lateral position.
Bilateral involvement is most common, but unilateral is not uncommon. Animals can be affected by the time they are 8 weeks of age. The most notable finding is a knock-knee (genu valgum) stance. The patella is usually reducible, and laxity of the medial collateral ligament may be evident. The medial retinacular tissues of the stifle joint are often thickened, and the foot can be seen to twist laterally as weight is placed on the limb. Sometimes you will notice a dog hopping or holding the leg up while he attempts to move the ligament back into place.
All Posey Canyon dogs used for breeding have had their Patella’s checked at one year of age by a Licensed Veterinarian and will be OFA Certified for normal Patellas.
PLLIs a genetic eye disorder found in many dog breeds. Parson Russell terrier breeders now have available to them a test which can identify carriers, affected dogs and dogs that are clear of the gene that produces PLL. It takes two carriers or a carrier and an affected to produce affected dogs. OFA lists on their website all dogs that have been tested and are clear. A person submitting DNA does have the option to have negative test results not listed, but if a breeder states their dogs are PLL clear they or their ancestors will be listed on the OFA website in their searchable database. Dogs whose parents are tested clear will not need to be tested as they will be clear. Terriers that are carriers can be bred to a clear mate and the resulting puppies will not be affected with PLL. Below is an article which explains the reason breeders might choose to keep a carrier in their breeding program.
Primary Lens LuxationPrinted with permission from the author Bonnie Edison
Primary Lens Luxation is a painful and blinding ocular condition within our breed. It is manifests itself between the ages of four and eight and ultimately is bilateral in nature. It is a condition in which the lenses are displaced, usually to the anterior due to the ligaments or zonules detaching. For breeders, it can be a disaster because it occurs after a terrier has been bred. In addition, because it causes severe pain and the possibility of glaucoma, the eye(s) must be either removed, or the lens removed surgically, or the dog euthanized.
Unfortunately, due to the cost factor for two surgeries and critical care needs immediately after, these loved terriers are euthanized. Until now, the breeder faced not only their own terrier being affected, but the possibility of offspring as well. The pet owners are devastated and the breeders with progeny from an affected terrier had to make critical decisions.
Fortunately, through much research and donated DNA, a marker for PLL has been found. Genetically, it is Autosomal Recessive and so educated breeders using this genetic marker can breed knowing the outcome of the progeny. (see chart courtesy of Lena Kjempengren, DVM).
Technically speaking from a scientific point of view, an affected terrier could be bred to a Clear creating all carrier offspring, and a carrier bred again to a Clear and the Clear offspring kept for the future of a bloodline.
Primary Lens Luxation is a painful and blinding ocular condition within our breed. It is manifests itself between the ages of four and eight and ultimately is bilateral in nature. It is a condition in which the lenses are displaced, usually to the anterior due to the ligaments or zonules detaching.
For breeders, it can be a disaster because it occurs after a terrier has been bred. In addition, because it causes severe pain and the possibility of glaucoma, the eye(s) must be either removed, the lens removed surgically, or the dog euthanized. Unfortunately, due to the cost factor for two surgeries and critical care needs immediately after, these loved terriers are euthanized.
I have been reading posts on forums regarding the general consensus of terriers that have tested as Carriers of PLL with great personal interest. I owned and bred from an affected terrier many years before she was PLL affected. In addition, I had the surgery to remove the lens performed on both eyes at separate times and she lived a very happy and functional life as my buddy until the age of fifteen and a half. For all these years, breeders have been crossing terriers based on educational guessing. Now, we have an accurate way to move forward.
This is how I personally feel about this genetic test. With the bloodlines available or those that I would infuse into my breeding program, I would use a carrier male or female judiciously if that terrier was of value to the future of my breeding program. The cost of loosing quality from a particular dog or bloodline is higher than the cost of breeding to a Carrier to Clear terrier and testing the litter. After testing the litter, I would hope there would be an outstanding PLL Clear pup to keep. Firstly, I breed for myself and try to have a 5 year plan when possible. If someone wishes to have a puppy to infuse into their breeding program, it’s a bonus. I think most breeders have a litter for personal reasons first.
This test is now a way for us to prevent producing an affected litter while continuing to build a PLL Clear line if necessary. (For the record, I have been very fortunate with all PLL Clear but one bitch that is a low risk carrier which will not be removed my program).
As I read posts and hear discussions, I hope breeders do not feel the need to cull carriers to be successful. I have not had one veterinarian suggest we remove the carriers, in fact, they felt it was a way to move forward with a carrier to maintain a kennel bloodline. By deleting that dog or bitch genetically from a breeding program, what will you (generic) be giving up in the total scheme of your bloodlines? Now that we have a test, now that we know when a carrier bred to a clear can produce clear or carrier, I would urge breeders to be honest, prudent, and rational. Breeders would be well advised to sit down, look at the pedigrees, write down their goals along with theterrier’s pro and con attributes and then make a long term decisions. The responsibility of breeders maintaining structural quality with genetic stability regarding PLL is now a reality. And to all the geneticists who worked so diligently to locate this marker, we say thank you.
The Effects of Genetic Testing: Constructive or Destructive?Every breed has genetic disorders. Finding tests that identify carriers of the genes which cause these disorders is a goal in all breeds. Once a genetic test is found, however, it is a double-edged sword: Its use can enable breeders to improve a breed or devastate it.
Without genetic tests, the number of dogs that can be identified as carriers is low, even though many dogs may be suspected of being carriers because they have relatives that are known to be affected. Without tests, though, genetic-disease control involves breeding higher-risk dogs to lower-risk dogs. Dog breeds have closed gene pools; in other words, the diversity of genes in a given breed is fixed. The number of dogs removed from consideration for breeding based on concerns regarding a specific genetic disease is usually low, and therefore does not greatly alter the breed’s gene pool, or diversity.
However, once a genetic test is developed that allows breeders to positively determine if a dog is a carrier of a defective gene, many owners are likely to remove carrier dogs from their breeding stock. Although doing so is human nature, this temptation must be overcome. Any quality dog that you would have bred if it had tested normal should still be bred if it tests as a carrier.
In such circumstances, carriers should be bred to normal-testing dogs. This ensures that affected offspring will not be produced. Carrier breeding stock should be subsequently replaced with normal-testing offspring that exceeds it in quality. If the only quality offspring is also a carrier, then use that offspring to replace your original carrier. You have improved the quality of your breeding stock, even though the defective gene remains in this generation. It is certainly true, though, that the health of the breed does depend on diminishing the carrier frequency and not increasing it. You should therefore limit the number of carrier testing offspring that you place in breeding homes. This does not mean, however, that you should prevent all of them from being bred. It is important to carry on lines. A test that should be used to help maintain breed diversity should not result in limiting it.
Consider All AspectsWe know that dogs carry some unfavorable recessive genes. The more genetic tests that are developed, the greater chance there is of identifying an undesirable gene in your dog. Remember, however, that your dog is not a single gene, an eye, a hip, or a heart. Your dog carries tens of thousands of genes, and each dog is a part of the breed’s gene pool. When considering a breeding, you must consider all aspects of the dog - such as health issues, conformation, temperament and performance - and weigh the pros and cons. When a good-quality dog is found to carry a testable defective gene, there is a better option than removing that dog from your breeding program. That option is to breed it, so that you can keep its good qualities in the gene pool, and then replace it in your program with a normal-testing dog.
There are breeders who contend that no more than 10 percent of carrier dogs should be removed from breeding in each generation. Otherwise, they say, the net loss to the gene pool would be too great. In fact, less than 10 percent of all dogs in a breed are ever used for breeding. Dog breeds do not propagate according to what is known as the Hardy-Weinberg equilibrium, where all members of a group reproduce and pass on their genes to the next generation. Breeders already place tremendous pressure on their gene pools through selective breeding decisions. Indeed, breeders who focus their selective pressure on the more elusive traits in their dogs, rather than on testable and predictable single-gene conditions, are right to do so.
The DangersIt is important that breed clubs educate their owners on how genetic tests should be properly interpreted and used. History has shown that breeders can be successful in reducing breed-wide genetic disease through testing and making informed breeding choices. You should remember, however, that there are also examples of breeds that have actually experienced more problems as a result of unwarranted culling and restriction of their gene pools.
These problems include: reducing the incidence of one disease and increasing the incidence of another by repeated use of stud dogs known to be clear of the gene that causes the first condition; creating bottlenecks and diminishing diversity by eliminating all carriers of a gene from the pool, instead of breeding and replacing them; and concentrating on the presence or absence of a single gene and not the quality of the whole dog.
Breeders are the custodians of their breed’s past and future. “Above all, do no harm” is a primary oath of all medical professionals. Genetic tests are powerful tools, and their use can cause significant positive or negative changes. Breeders should be counseled on how to utilize test results for the best interests of the breed.
Jerold S Bell, DVM
(This article is reproduced here with the written permission of the author. Jerold.Bell@tufts.edu )
Paul Sherlie, DVM
Posey Canyon uses for
State University Small Animal Hospital
Operations & Educational Services
School of Veterinary Medicine
Disease Control ( GDC )
Kennel Club Canine Health Foundation
Greg Keller, Executive Director