Clearances and Permanent Identification of Labradors
The following provides information on means of permanent identification and clearances that breeders are using to determine genetic problems in Labradors:
- CERF - Canine Eye Registration Foundation
In operation since 1974, CERF is a voluntary non-profit organization organization dedicated to eliminating heritable eye diseases in purebred dogs through research, education and management of a centralized, national registry. CERF cooperates with member of the American College of Veterinary Ophthalmologists (A.C.V.O. ) to register those dog's certified free of heritable eye disease and also collects data on all dogs examined by certified veterinary ophthalmologists in order to research trends in eye disease and breed susceptibility. After a painless examination of the dog’s eyes, the A.C.V.O. specialist completes the CERF form and indicates any specific diseases found. If the dog is certified to be free of heritable eye disease and has a permanent identification in the form of microchip, tattoo or DNA profile, it can then be registered with CERF. The certification is good for 12 months from the date of the exam and afterwards the dog must be reexamined and recertified annually to maintain its' registration with CERF. Regardless of the outcome of the dog's exam, results will be sent to CERF where information will be entered into the database for that specific breed. This information will be used in generating research reports, but the individual dog's identities will become confidential and will never be released. The American Kennel Club incorporates CERF numbers on their registration papers and certified pedigrees.
Because CERF provides a determination of the physical presence (phenotype) of eye disease but not the dog’s genetic makeup, there has been much interest in development of DNA-based tests that can detect carriers of eye diseases. Research in Labrador Retrievers has concentrated on a method to detect carriers of the prcd mutation which causes Progressive Retinal Atrophy or PRA. The currently marketed OptiGen test is a marker test which does not actually detect the prcd mutation but detects patterns on a chromosome near the prcd gene. Although this test provides reliable identification of those dogs which are "genetically clear", some uncertainties remain about the use of the test to identify dogs which are carriers for prcd or are affected by prcd. Because the OptiGen test is a marker-based test, it can produce a "false-allele" reading. This means that now and then, a dog testing as carrier may actually be clear. And sometimes a dog testing as affected may prove to be a carrier. However, a dog testing as normal will always be clear. If PRA affected status is suspected, it is recommended that other techniques such as electroretinography (ERG) be used by a veterinary eye specialist. Meanwhile, more research is being done to determine more precisely the frequency of the false allele and to develop more accurate tests to detect the prcd mutation.
- PennHIP
- This program is a collaborative effort of the Veterinary School at the University of Pennsylvania, Synbiotics Corporation (formerly ICG) and a network of more than 750 certified PennHIP-trained veterinarians. PennHIP's primary objective is to reduce the frequency and severity of hip dysplasia in all breeds of dogs. PennHIP is attempting to accomplish this goal through the implementation and widespread utilization of a stress-radiographic technique (X-ray). The PennHIP method involves special positioning of the dog so that the dog’s passive hip laxity, or "looseness" of the hip ball in the hip socket, can be accurately measured and the presence of degenerative joint disease (DJD) detected. Three separate radiographs are made: the distraction view, the compression view and the hip-extended view. These views are used to obtain accurate and precise measurements of hip joint laxity, congruity (the "fit" of the ball in the socket) and the existence of DJD in the hip joint, respectively. The PennHIP method can be performed on dogs as young as sixteen weeks of age. Specially trained veterinarians submit all radiographs, whether good or bad, to PennHIP for evaluation. Interpretations of radiographs become part of a medical database but remain confidential unless specified otherwise by the dog’s owner.
- Wind Morgan
- Initiated in 1990 at the University of California-Davis, this program provides a mechanism for othropedic evaluation of heritable joint diseases in the Labrador Retriever. During the past 15 years it has become apparent that severe problems exist with heritable disease of the hips (hip dysplasia), shoulder (OCD), elbow (dysplasia), and hock (OCD) joints in Labradors.Radiography (x-rays) are used to diagnose the presence of hip and elbow dysplasia, shoulder OCD and hock OCD. The absence of these diseases in the hips, elbows, shoulders, and hocks can usually be accurately determined at 12 months of age, although preliminary evaluations of these joints can be made as early as 6 months of age. Radographs can be made by any veterinary practitioner or technician, and should be submitted to the Wind-Morgan program for evaluation with a completed application form and a copy of the dog's three generation pedigree. If an individual is found to be normal in all four joints at or beyond the age of 12 months, a Wind-Morgan number will be issued. Copies of the evaluations will be made to both the dog's owner and to the veterinarian responsible for taking the films. Additionally, results of the study will be entered into the computer base at the Institute for Genetic Disease Control (GDC), for inclusion in their open registry for genetic and statistical analysis. This program was closed in August 2002, but the data collected continues to be available to researchers.
- OFA - Orthopedic Foundation for Animals
The OFA, established in 1966, is a non-profit organization originally created to assist breeders in addressing hip dysplasia. In recent years OFA has added databases to assist breeders in assessing elbow and patella deformities, craniomandibular osteopathy, autoimmune thyroiditis, congenital heart disease, and DNA databases.
The OFA's voluntary database is the world's largest all-breed data bank on radiographic evaluations of the hip. Radiographs of animals 24 months of age or older are independently evaluated by three randomly selected, board-certified veterinary radiologists from a pool of 20 to 25 consulting radiologists throughout the USA. Each radiologist evaluates the animal's hip status considering the breed, sex, and age. The hip grades of excellent, good and fair are within normal limits and are given OFA numbers. This information is accepted by AKC on dogs with permanent identification (e.g tatoo, microchip) and is in the public domain. Radiographs of borderline, mild, moderate and severely dysplastic hip grades are reviewed by the OFA radiologist and a radiographic report is generated documenting the abnormal radiographic findings. Unless the owner has chosen the open database, dysplastic hip grades are closed to public information.
Elbow dysplasia is also evaluated by OFA using radiographs. For elbow evaluations, there are no grades for a radiographically normal elbow. The only grades involved are for abnormal elbows with radiographic changes associated with developmental degenerative joint disease (elbow dysplasia). Like the hip certification, the OFA will not certify a normal elbow until the dog is 2 years of age. The OFA also accepts preliminary elbow and hip radiographs for dogs less than 2 years of age.
The OFA maintains a registry for autoimmune thyroiditis which is the most common cause of primary hypothyroidism in dogs. The disease has variable onset, but tends to clinically manifest itself at 2 to 5 years of age. As a result of the variable onset of the presence of autoantibodies, periodic testing is necessary. Since the majority of affected dogs will have autoantibodies by 4 years of age, annual testing for the first 4 years is recommended. After that, testing every other year should suffice. Dogs can be examined by an attending veterinarian and have a serum sample sent to an OFA approved laboratory for testing. A certificate and breed registry number will be issued to all dogs found to be normal at 12 months of age. Ages will be used in the certification process since the classification can change as the dog ages and the autoimmune disease progresses.
The OFA cardiac database gathers data regarding congenital heart diseases in dogs and identifies dogs which are phenotypically normal. Normal dogs are those without a cardiac murmur or one with an innocent heart murmur that is found to be otherwise normal by virtue of an echocardiographic examination which includes Doppler studies. Cardiac auscultation is the primary screening method for initial identification of CHD. In order to be certified each dog is examined and classified by a veterinarian with expertise in the recognition of canine congenital heart disease. Preliminary evaluation of dogs under 12 months of age can be done but full certification requires subsequent examination at 12 months of age or older. OFA maintains a data bank of information for those found to be normal.
Identification of dogs that have normal patellas is the purpose of the OFA patellar luxation registry. In patellar luxation, the kneecap luxates, or pops out of place. Each dog is examined awake, without chemical restraint, and classified by an attending veterinarian according to OFA instructions. Evaluation can be done under 12 months of age if desired by the owner.
The following are ways in which dogs can be permanently identified:
- DNA Analysis
- The use of certain genetic markers in a dog's DNA for the production of a unique genotype provides a method of absolute identification of individual dogs and parentage verification from one generation to the next. A dog's genetic constitution, called a "genotype," can be determined by an analysis of a simple bristle swab swirled against the inside cheek portion of a dog's mouth. The AKC has initiated a program by which breeders can now have their dogs voluntarily DNA certified. A Certificate of DNA Analysis is issued with the dog’s name, registration information, DNA Profile Number, and genotype. If the dog is registered, Registration Certificates and Pedigrees issued after the dog has been DNA certified will contain the DNA Profile Number. The AKC has also initiated a Frequently Used Sires Program in which every sire producing seven or more litters in his lifetime or producing more than three litters in a calendar year must be 'AKC DNA Certified.' Dogs with DNA profiles from the voluntary DNA Certification Program or from the Parent Breed Club Program have already met this requirement. Furthermore, AKC DNA Certification is required for all stud dogs collected for fresh extended and frozen semen use, including foreign stud dogs collected for imported semen use in the UnitedStates.
- Tattooing and Microchipping
- Permanent identification by tatoo or microchip not only provides a means to recover a dog if it is lost but it also satisfies the AKC’s policy for record keeping and identification. A microchip is a rice-sized device encoded with a unique and unalterable identification number. The "chip" is implanted just under the skin in the scruff of the neck and is read by a scanner. The identifying microchip number must be noted on the dog or litter record. If microchips are used as the primary means of identification, a scanner must be present at all times if there are more than 20 dogs over six months of age on the premise. Microchip identification is not required in any way for AKC registration or to participate in AKC approved events. Tattoos remain an acceptable form of identification to comply with AKC’s rules.
