Health, what you should Know
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Von Willebrand disease (vWD) is the most common inherited bleeding disorder found in dogs. Affected dogs have increased bleeding due to either abnormal levels of, or function of, the von Willebrand factor (vWF), an important component in the blood clotting process. There are three forms of the disease, types I, II, and III. In type III vWD, affected dogs are unable to produce any von Willebrand factor which results in severe and abnormal bleeding. Dogs may develop life-threatening bleeding with an accidental injury or any surgical procedure.
Genetic testing of the VWF gene in affected breeds will reliably determine whether a dog is a genetic Carrier of Von Willebrand disease type III. Von Willebrand disease type III is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs do not have any features of the disease but when bred with another dog that also is a carrier of the same Mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Dogs that are not carriers of this mutation have no increased risk of having affected pups.
Trapped Neutrophil syndrome (TNS) is an inherited disease that affects the dog’s immune system and its ability to fight infection. Affected dogs have normal white cell production in the bone marrow, but are unable to release the cells into the blood where they are needed to fight infection. Symptoms and age of onset of the disease varies and is dependent on the specific infection that the dog is fighting. Affected dogs will eventually die from an infection and generally do not survive past six months of age.
Genetic testing of the VPS13B gene in Border Collies will reliably determine whether a dog is a genetic Carrier of trapped Neutrophil syndrome. Trapped neutrophil syndrome is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs do not have any features of the disease but when bred with another dog that also is a carrier of the same Mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Border Collies that are not carriers of the mutation have no increased risk of having affected pups.
Spongiform leukoencephalomyelopathy is a progressive, early-onset, inherited neurologic condition affecting dogs. Affected dogs typically present between 1 to 9 weeks of age depending on the breed with signs of neurologic disease. Affected puppies are smaller than littermates and symptoms initially start with tremors and progress to Ataxia as the puppies learn to walk. They have difficulty controlling leg movements and keeping their balance until they eventually can’t walk. Later in the course of disease they may have difficulty eating, salivate excessively, and have seizures. Affected puppies that do not die on their own are euthanized within 15 weeks of age due to a poor quality of life.
Progressive retinal Atrophy, progressive Rod-cone degeneration (PRA-prcd) is a late onset, inherited eye disease affecting many breeds of dog. PRA-prcd occurs as a result of degeneration of both rod and cone type Photoreceptor Cells of the Retina, which are important for vision in dim and bright light, respectively. Evidence of retinal disease in affected dogs can first be seen on an Electroretinogram around 1.5 years of age for most breeds, but most affected dogs will not show signs of vision loss until 3 to 5 years of age or later. The rod type cells are affected first and affected dogs will initially have vision deficits in dim light (night blindness) and loss of peripheral vision. Over time affected dogs continue to lose night vision and begin to show visual deficits in bright light. Other signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the retina called the Tapetum that can be observed on a veterinary eye exam. Although there is individual and breed variation in the age of onset and the rate of disease progression, the disease eventually progresses to complete blindness in most dogs. Other inherited disorders of the eye can appear similar to PRA-prcd. Genetic testing may help clarify if a dog is affected with PRA-prcd or another inherited condition of the eye.
Genetic testing of the PRCD gene will reliably determine whether a dog is a genetic Carrier of PRA-prcd. PRA-prcd is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of being a carrier of the PRCD gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups. However, because there are multiple types of PRA caused by mutations in other genes, a normal result in PRCD does not exclude PRA in a pedigree.
Genetic testing of the CYTB gene will reliably determine whether a dog is a genetic Carrier of spongiform leukoencephalomyelopathy. Spongiform leukoencephalomyelopathy is a mitochondrial disorder. Dogs only inherit mitochondrial DNA from the mother. Because this disease is inherited in a maternal inheritance pattern, both male and female dogs must inherit the mutated gene from the mother to develop the disease. Affected male dogs do not pass their mitochondrial DNA to their offspring and cannot produce affected pups. Each pup that is born to a female dog carrying a Mutation in the CYTB gene is at risk of having the disease. However, the ratio of mitochondria without the mutation to the number of mitochondria with the mutation is important in determining whether a specific dog will actually develop features of the disease. Reliable genetic testing is important for determining breeding practices. Because disease presentation is variable, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of carrier or affected dogs is not recommended. Female dogs that are not carriers of the mutation have no increased risk of having affected pups.
Primary ciliary dyskinesia (PCD) is an inherited disorder of the cilia, the hair-like structures that line the respiratory system. Normal cilia move in wave-like patterns to aid the movement of fluids, filter pathogens, and protect the respiratory system. In PCD, affected dogs have cilia that are either malformed or do not move. Fluids cannot be moved in the respiratory tract and can lead to infection. Symptoms include coughing, sneezing, nasal discharge and frequent respiratory infections. The disorder also affects the sperm causing it to be immotile and affected dogs are sterile.
Genetic testing of the CCDC39 gene in Old English Sheepdogs will reliably determine whether a dog is a genetic Carrier of primary ciliary dyskinesia (PCD). PCD is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs do not have any features of the disease but when bred with another dog that also is a carrier of the same Mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Old English Sheepdogs that are not carriers of the mutation have no increased risk of having affected pups.
The neuronal ceroid lipofuscinoses (NCLs) are a group of rare inherited lysosomal storage disorders. Affected dogs lack a specific Enzyme necessary for normal metabolism. As a result, there is an abnormal accumulation of waste compounds primarily in the cells of the nervous system, leading to a range of nervous system disorders. Neuronal ceroid lipofuscinosis 6 (NCL6) is an early-onset disorder affecting Australian Shepherds. Affected dogs present with progressive loss of vision, especially in low light. Other symptoms include a lack of muscle coordination, abnormal gait, tremors and aggressive behavior. There is currently no treatment for the disease.
Genetic testing of the CLN6 gene in Australian Shepherd dogs will reliably determine whether a dog is a genetic Carrier of neuronal ceroid lipofuscinosis 6 (NCL6). NCL6 is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs do not have any features of the disease but when bred with another dog that also is a carrier of the same Mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Australian Shepherds that are not carriers of the mutation have no increased risk of having affected pups.
Multifocal retinopathy 1 is an inherited disorder of the Retina known to occur in numerous breeds. This disease causes changes to the retina that can be detected on an ophthalmology exam. Affected dogs present with numerous circular patches of the retina that appear elevated due to accumulation of material on the retina. These blister-like lesions can appear gray, tan, or pink in color and can vary in size and location. Retinal changes can appear as early as 4 months of age and progression of retinal changes is variable and can be slow. Some affected dogs may have lesions that appear to heal and disappear but may reappear again later. Retinal changes in this disease may affect vision. Nonprogressive multifocal bullous retinal detachments are common.
Genetic testing of the BEST1 gene in at risk dogs will reliably determine whether a dog is a genetic Carrier of multifocal retinopathy 1. Multifocal retinopathy 1 is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs do not have any features of the disease but when bred with another dog that also is a carrier of the same Mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. At risk dogs that are not determined to be carriers of the mutation have no increased risk of having affected pups.
Intestinal cobalamin malabsorption (group B) is an inherited disease affecting Border Collies. Affected dogs are unable to make adequate amounts of a protein that plays a role in absorption of certain nutrients from the intestinal tract and kidneys, including the B vitamin, cobalamin. Affected dogs have increased levels of methylmalonic acid in their urine (a sign of cobalamin deficiency) from as early as 14 weeks of age, but symptoms of disease may not be recognized by owners for months or years. Symptoms of disease include anorexia, lethargy, poor weight gain, poor muscle mass, and in rare circumstances, a severe neurological dysfunction called hepatic encephalopathy that can lead to altered mental state, seizures, coma and death. Affected dogs have an increase in certain proteins in their urine, and have decreased synthesis of blood cells resulting in Anemia and decreased numbers of neutrophils. Affected dogs require cobalamin supplementation for life that results in disease remission for most animals within a few weeks. Though not associated with clinical disease, affected dogs will continue to pass increased amounts of certain proteins in the urine even with cobalamin supplementation.
Genetic testing of the CUBN gene in Border Collies will reliably determine whether a dog is a genetic Carrier of intestinal cobalamin malabsorption (group B). Intestinal cobalamin malabsorption (group B) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the CUBN gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Border collies that are not carriers of the mutation have no increased risk of having affected pups.
Hyperuricosuria is an inherited condition of the urinary system affecting several breeds of dog. The SLC2A9 gene codes for a protein that allows the kidneys to transport uric acid from the urine. Dogs with mutations in both copies of the SLC2A9 gene are predisposed to have elevated levels of uric acid in the urine, hence the name hyperuricosuria. Uric acid can form crystals and/or stones (uroliths) in the urinary tract. Dogs with hyperuricosuria most commonly present with symptoms of recurrent urinary tract inflammation, which include frequent urination, blood in the urine, and straining to urinate. They may also have loss of appetite, lethargy, weakness, vomiting and pain. Urinary stones in the bladder can cause urinary tract infections or more seriously, blockage of the Urethra. Both male and female dogs can be affected, but obstruction of urine flow is more common in males due to differences in anatomy. Although an x-ray can be used to exclude other types of stones, urate stones cannot typically be seen using x-rays and must be evaluated by ultrasound. Not all dogs with mutations in both copies of the SLC2A9 gene will have symptoms of disease, though they will have increased uric acid excretion in the urine.
Genetic testing of the SLC2A9 gene will reliably determine whether a dog is a genetic Carrier of hyperuricosuria. Hyperuricosuria is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the SLC2A9 gene mutation. Reliable genetic testing is important for determining breeding practices. Because not all affected dogs will have clinical signs associated with hyperuricosuria, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
Gallbladder mucoceles are a rare problem found in several breeds of dogs. Dogs usually present with vomiting, loss of appetite and abdominal pain. A mucocele in the gallbladder results in an abnormally distended gallbladder that contains excessive mucus. It can result in inflammation and possible rupture of the gallbladder. If the gallbladder is not removed before rupture, the dog may become very ill and die. Because gallbladder mucoceles have symptoms that are common to other diseases, it can be difficult to diagnosis without ultrasonography or surgery.
Genetic testing of the ABCB4 gene will determine whether a dog is at risk to potentially develop gallbladder mucoceles. Gallbladder mucoceles are suspected to be inherited in an Autosomal Dominant manner in dogs, but appear to have Incomplete Penetrance. Dogs identified to have the genetic change are at risk of developing features of the disease. For each pup that is born to an affected dog, there is a 50% chance of inheriting the disease Mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of affected dogs is not recommended. Dogs that are not found to have this mutation have no increased risk of having affected pups.
The dilute Locus (D-locus) corresponds to a region of the MLPH gene that when mutated results in a “diluting” or lightening of the coat color of dogs. The Mutation is recessive, meaning that two mutant copies of the MLPH gene (one from each parent) are required to develop a diluted coat color. This gene modifies other regions of the genome responsible for controlling the expression of the pigments, eumelanin and pheomelanin, in the hair. Canine coat color determination is complex due to interactions of multiple genes responsible for both color and anatomic placement of the color. A dog with two mutant copies at the D-locus will have a blue, gray, Isabella (lilac), fawn, silver or pale brown coat color depending on the other coat color genes present in the individual.
Disease Association Note: Mutations of the D-locus are sometimes responsible for a condition called color dilution Alopecia, black hair follicular dysplasia, or blue Doberman syndrome (depending on the breed) because dilute coat color can be associated with development of alopecia (hair loss). The clinical presentation of alopecia associated with dilute coat color is variable within and between breeds; therefore only a portion of individuals carrying two copies of the mutated MLPH gene will show hair loss with some breeds being much more likely to develop the condition. Though two copies of the mutant gene are necessary to develop color dilution alopecia, the variable presentation of this condition suggests that additional environmental or genetic factors contribute to the development of alopecia. Dogs affected with alopecia typically present with loss of hair between the ages of four months and two years. Hair of affected dogs can also appear dry and dull. The hair loss is caused by abnormal Melanin storage in the hair, which leads to breakage of the hair shaft and the lack of normal regrowth of hair. Dogs with this condition can also be affected with recurrent bacterial skin infections originating in the hair follicles (folliculitis). Given that the modifying environmental or genetic factors responsible for alopecia are unknown, the only way to prevent color dilution alopecia is to avoid transmitting the dilute coat color mutation to offspring in susceptible breeds.
Exercise-induced collapse (EIC) is an inherited neuromuscular disorder that presents as exercise intolerance in apparently healthy young adult dogs. Affected dogs appear normal and active and do not have decreased muscle mass. However, these dogs will experience signs of EIC shortly after strenuous exercise and will begin to walk with a wobbly, uncoordinated gait. In some circumstances, the symptoms of collapse can progress to full body weakness, rigid limbs, confusion, loss of consciousness, seizure, and very rarely, death. The episodes typically last 5-10 minutes and most dogs will completely recover within 45-60 minutes.
Genetic testing of the DNM1 gene will reliably determine whether a dog is a genetic Carrier of exercise-induced collapse (EIC). EIC due to DNM1 Mutation is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs are not believed to have any features of the disease but when bred with another dog that also is a carrier of the same mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Dogs that are not carriers of this mutation have no increased risk of having affected pups.
Dilated cardiomyopathy is an inherited disorder of the heart affecting several breeds of dog. This disease shows Incomplete Penetrance, meaning that not all dogs at risk (those with two copies of the Mutation) will develop the disease. In affected dogs, the heart muscle is weak and the chambers become dilated with thin walls. These enlarged hearts have poor contractility and are prone to arrhythmias. Affected dogs present with clinical signs of poor heart function between 1 to 8 years of age. Affected dogs develop clinical signs as they age ranging from mild exercise intolerance to sudden death or congestive heart failure. Signs of heart disease include exercise intolerance, fatigue, coughing, difficulty breathing, rapid breathing, fainting and sudden death. Affected dogs that don’t die suddenly from arrhythmias usually die from congestive heart failure around 7 years of age. Different disease genes and environmental factors play a role the development of dilated cardiomyopathy in dogs. Therefore not all dogs with this disease will have the same genetic mutation.
Genetic testing of the PDK4 gene will reliably determine whether a dog is a genetic Carrier of the PDK4 Mutation associated with dilated cardiomyopathy. Dilated cardiomyopathy due to this mutation is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting two copies and a 50% chance of inheriting one copy and being a carrier of the PDK4 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms may not appear until adulthood and not all dogs with two copies of the mutation develop disease, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended.
Cone degeneration (group A) is an inherited eye disease affecting dogs. Affected dogs develop day blindness (blindness in bright light) and Photophobia (light sensitivity) between 8 to 12 weeks after birth due to degeneration of cells in the eye called cone photoreceptors which are responsible for vision in bright light. Affected dogs have normal vision in low light and structures of the inner eye appear normal on eye exam. Normal cone cell function can be seen on Electroretinogram (ERG) before six weeks of age, but becomes abnormal between 6 to 12 weeks of age and is completely absent in affected adult dogs signifying complete loss of Cone Cells. The cells responsible for vision in low light called Rod photoreceptors are not affected and thus, affected dogs will still be able to see normally in low light throughout life.
Genetic testing of the CNGB3 gene will reliably determine whether a dog is a genetic Carrier of cone degeneration. Cone degeneration is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the CNGB3 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.
Multidrug resistance 1, also called MDR1, is an inherited condition affecting several breeds of dogs, especially herding dogs or descendants of herding breeds. The Mutation in the ABCB1 gene associated with MDR1 causes dysfunction of P-glycoprotein, which is responsible for removing certain drugs and toxins from the body. Clinical signs are most commonly associated with distribution of the drug in the central nervous system. If an at-risk dog is treated with one of several common drugs (see below*), they are at risk of developing neurologic symptoms that could range from tremors, excess salivation, anorexia, and blindness to coma and even death. Because of the defective ability to metabolize specific drugs, these drugs can be lethal even at low doses. The MDR1 mutation does not cause adverse effects in dogs unless the dog is exposed to these drugs. Therefore, veterinarians should be notified when a dog is at risk for multidrug resistance 1 prior to administration of any medications.
*Drugs known to cause neurological signs related to the MDR1 mutation:
Acepromazine, butorphanol, doxorubicin, emodepside, erythromycin, ivermectin, loperamide, milbemycin, moxidectin, rifampin, selamectin, vinblastine and vincristine.
In addition to this list, there are many other drugs known to be removed from the central nervous system via the P-glycoprotein mechanism in humans. However, reports of neurological dysfunction related to drugs other than those listed here are scarce in dogs. Please consult your veterinarian prior to giving drugs to known multidrug resistance carriers, affected dogs, or untested dogs of breeds commonly affected with this condition.
Degenerative myelopathy caused by Mutation of the SOD1 gene is an inherited neurologic disorder of dogs. This mutation is found in many breeds of dog, including the Rough Collie. While it is not clear for some of the other breeds, Collies are known to develop degenerative myelopathy associated with this mutation. The variable presentation between breeds suggests that there are environmental or other genetic factors responsible for modifying disease expression. The average age of onset for dogs with degenerative myelopathy is approximately nine years of age. The disease affects the White Matter tissue of the spinal cord and is considered the canine equivalent to amyotrophic lateral sclerosis (Lou Gehrig’s disease) found in humans. Affected dogs usually present in adulthood with gradual muscle Atrophy and loss of coordination typically beginning in the hind limbs due to degeneration of the nerves. The condition is not typically painful for the dog, but will progress until the dog is no longer able to walk. The gait of dogs affected with degenerative myelopathy can be difficult to distinguish from the gait of dogs with hip dysplasia, arthritis of other joints of the hind limbs, or intervertebral disc disease. Late in the progression of disease, dogs may lose fecal and urinary continence and the forelimbs may be affected. Affected dogs may fully lose the ability to walk 6 months to 2 years after the onset of symptoms. Affected medium to large breed dogs, such as the Rough Collie, can be difficult to manage and owners often elect euthanasia when their dog can no longer support weight in the hind limbs.
Breed-Specific Information for the Rough Collie
The Mutation of the SOD1 gene associated with degenerative myelopathy has been identified in Rough Collies. The exact frequency of this disease and approximate age of disease onset are unreported for Rough Collies. However, 25.8% out of 151 Collies tested were carriers of the mutation and 25.8% were at-risk/affected.
Von Willebrand’s disease (vWD) is the most common inherited bleeding disorder found in dogs. Affected dogs have increased bleeding due to either abnormal levels of, or function of, the von Willebrand factor (vWF), an important component in the blood clotting process. There are three forms of the disease, types I, II, and III. In type II vWD, affected dogs have a normal amount of the von Willebrand factor but it is structurally deformed and therefore cannot function properly. As a result, dogs can have excessive bleeding after an injury or surgical procedure.
Genetic testing of the VWF gene in affected breeds will reliably determine whether a dog is a genetic Carrier of Von Willebrand disease type II. Von Willebrand disease type II is known to be inherited in an Autosomal Recessive manner in dogs. Carrier dogs do not have any features of the disease but when bred with another dog that also is a carrier of the same Mutation, there is a risk of having affected pups. For each pup that is born to this pairing, there is a 25% chance of having the disease. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers is not recommended. Dogs that are not carriers of this mutation have no increased risk of having affected pups.
Autoimmune disease has been a concern in Collies for as long as I can remember. In the past dogs died from 'kidney disease' or 'liver failure' and now we know it is probably these individuals may have been suffering from Addison's disease or Haemolytic Anaemia.
Auto immune disease is rare but Collies ,and many other breeds, have a predisposition to develop various forms. At the moment all we know is that several elements come into play when a dog develops an AI disease. There has to be a genetic predisposition but there must also be environmental factors that trigger the disease. If the environmental factor is not encountered even those dogs with the highest genetic predisposition will not go on to develop a health problem. The environmental factor is probably a virus or group of viruses but it could be any form of stress the dog encounters, from breaking a leg to coming into season or rearing a litter of puppies.
Dr Lorna Kennedy, senior scientist at the Centre for Integrated Genomic Research at the University of Manchester. She has spent the past 20 years working on the Major histocompatibility Complex region of the genome in dogs and wolves. The MHC plays an important role in the immune system of all mammals and, as in humans, MHC associations have been identified in most canine auto immune disease. Within the MHC there is a region called the Dog Leucocyte Antigen (DLA), a set of three variable polymorphic genes that are inherited from each parent. These sets are referred to as haplotypes and, in line with most breeds, Collies have about five different haplotypes. Also in common with other breeds, one of these haplotypes is more common than the others. In collies this is haplotype 1 and is carried by more than 40 per cent of the breed. Haplotypes can predispose a dog to developing a particular auto immune disease but act as a 'protective' against it developing another. Haplotype 1, for example, is thought to be a risk factor for SLO but seems to be protective against Addison's disease. Haplotype 3 appears to carry greater risk for the development of Addison's disease and, in many breeds, haplotype 4 has been implicated with auto immune haemolytic anaemia.
Sadly all this information does not mean we can go test our dogs for their haplotype status, breed accordingly and live happily ever after.
The haplotypes do not work on their own but are affected by around 40 other genes and by all important environmental factors such as viruses. If a dog has all the genetic markers to predispose it to a particular disease but is lucky enough never to encounter the trigger factor it will remain healthy. And a dog with a haplotype that predisposes it to a particular disease but without the multiple other genes involved will also remain unaffected even if it encounters the virus.
Dr Kennedy explained that is was very unlikely that there would be a genetic test that would advise breeders on which dogs would produce AI disease. The most we can hope for is a test that will give a percentage risk of what a dog will produce. Percentages can be difficult to work with. A ten per cent chance of venturing out in the rain without a coat and getting caught in a shower might seem a much less risk than having one puppy in a litter of ten destined to suffer a dreadful disease. We might even find ourselves in the position of having to evaluate, for example, the risk of developing hypothyroidism, which is relatively easy to treat and manage and the risk of developing Addison's disease which, whilst manageable, can have more devastating effects.
Dr Kennedy emphasized the importance of maintaining all haplotypes. A common haplotype is probably common for a good reason - it give protection. A rare haplotype might be rare for a good reason, being detrimental to the dog. At the moment we don't know enough to take the huge risk of trying to eliminate any haplotype. It would probably be a good idea to breed dogs with a particular haplotype to dogs with an alternate set. However, testing is expensive
It is interesting that the same haplotype can have different effects in different breeds. Although we should be working to make the best of our gene pool we must also consider the fact that introducing a 'new' haplotype might also introduce diseases that we currently don't have. In the same way, working to increase the incidence of a minority haplotype might have the unwanted effect of increasing the incidence of a disorder that is currently rare.
There may never be a DNA test that will identify the dogs most likely to produce auto immune disease. We may eventually have a test that will give us a 'percentage chance' of a particular dog developing a particular disease but even that is some years in the future.
What we can do is to adapt our breeding program to ensure we make the best use of the genes we have available. We must work to reduce the average co-efficient of inbreeding within the breed. COI represent the likelihood of a dog inheriting identical genes from the same individual ancestor. In collies it is common to find a dog has 20 or more lines back to an individual stud dog of years gone by, 16 or more lines back to a second dog, 14 or more back to a third dog and so on. This gives the breed a COI that is higher than average and which we must work to reduce.
What Can We Do ?
The first and most obvious step is the reduce the use of popular stud dogs. The popular stud dogs of today are the high COI of tomorrow. In my opinion no dog should be used more than an absolute maximum of 10-15 times in its lifetimes, given the breed's annual rate of production of less than 600 puppies. Some stud dogs have produced well over 400 puppies in their lifetimes and this is simply unacceptable. They may be great sires of many champions but production at that level is harmful to the future of the breed as a whole. There is absolutely no criticism of breeders of past years who have allowed their dogs to be used 40, 80 or even 100 times at stud. Knowledge evolves and as it evolves we must make use of it for the benefit of the breed we love.
Breeders should do their best to ensure the COI of litters bred are lower than the COI of the parents.
Some early lines in the UK have been underused and where these lines exist overseas it would be valuable to import them back into the UK.
Dogs affected by any auto immune disease should not be bred from. Mating’s that produce progeny affected by auto immune disease should not be repeated.
We may never be able to eradicate auto immune disease but by ensuring our dogs have as wide a gene pool as possible we give them a better chance of being heterozygous - that is having different genes at the same locus. If one gene is faulty the chances are it’s 'pair' will be healthy and the dog will have a far greater chance of a healthy life. The big challenge to breeders of the future will be to maintain breed type at the same time as promoting a wider gene pool and consequent low COI. In my opinion the best way of achieving this will be to breed for 'type' without discounting dogs because their lines do not 'tie in' with those of the bitch.
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Cryptorchidism is a hereditary condition that can be passed on from affected sires and dams to their male and female young (only the male offspring can actually display the disorder because female offspring do not have testicles, however, affected female offspring can carry the genes through to the next generation thereby passing the disorder on).
The specific gene or genes that produce cryptorchidism in the dog and cat have not yet been positively identified as far as I know (i.e. there is not yet a genetic screening test that can be performed to detect cryptorchidism-affected and cryptorchidism-gene-carrier animals). There is even still conjecture about whether just one defective gene or many defective genes are responsible for the defect.
What has been determined to some extent is the mode of inheritance in the dog. I use the words "to some extent" because even the mode of inheritance of canine cryptorchidism has been difficult to establish for certain. At the current time, cryptorchidism is thought to have an autosomal recessive mode of inheritance in the dog. The mode of inheritance has not been so well studied and determined in the cat, but is thought to be similar to the dog.
A primer on basic genetics:
Before I can discuss the implications and consequences of an autosomal recessive mode of inheritance, I need to give you a basic overview of simple genetic principles.
All human and animal cells contain DNA. DNA is a long sequence of four different kinds of molecules (A,T,C,G) which can be arranged into millions of different combinations of varying lengths to code for all of the genes in a body. The information contained in each DNA gene sequence is used by the cell as a template or set of instructions by which that cell is able to manufacture certain important proteins and molecules vital to cellular function, replication and survival. Genes code for pretty much everything in the body: from the production of vital hormones (e.g. insulin, growth hormone, cortisol, testosterone) to the production of enzymes used in important cellular chemical reactions to the production of proteins and compounds that imbue humans and animals with their important body traits (e.g. eye colour, hair colour, coat length, coat softness, body size, baldness and so on).
, there is a gene or a number of genes responsible for making the testicle descend into its normal scrotal location in early life. This might be a gene with a role in testosterone production - after all, sufficient testosterone production is thought to assist normal testicular descent (hence the medical use of GnRH or hCG to try to correct cryptorchidism). Alternatively, it might even be a gene with a role in normal gubernaculum development (e.g. a gene responsible for making normal gubernaculum contractile proteins) - after all, a normally-regressing gubernaculum is required in order for the testicle to descend. Correct testicular descent could and is likely to be a combination of many different genes all working together. A defect in any one of these genes, which prevents the cells from working correctly and making the right gene-coded products (e.g. prevents them from producing the right molecular forms of testosterone; prevents them from producing enough testosterone; prevents them from producing normal gubernacular contractile proteins ...) could result in a failure of normal testicular descent and, therefore, cryptorchidism.
To make matters more complex, every cell in the body does not merely contain just one set of all of the genes, but two. One set from the animal's mother and a second set from the animal's father. This means that, for every single gene-coded trait that exists in a body, there are two possible parental gene combinations that could code for it. This is where the issue of inheritance comes in - animals and humans inherit genes and, therefore, traits from both of their parents. For example, an animal might inherit a gene coding for blue eyes from its father and a gene coding for brown eyes from its mother. Either gene could be switched on in that animal, giving the offspring animal blue eyes or brown eyes. Which color actually gets expressed by the young animal's eyes really depends on the nature of the different genes themselves (the gene for blue versus the gene for brown) and which is the more dominant gene. If the gene for blue eyes is a dominant gene, then the mother's gene for brown eyes will not be expressed in that young animal (the non-expressed brown eye gene is termed a recessive gene) and it will display blue eyes. The young animal will be a carrier of the brown eye gene (it might even pass the brown eye gene onto its own offspring, giving them brown eyes) but it will not have brown eyes itself because of the overpowering dominance of the blue gene.
In the case of cryptorchidism, the defective gene (or genes) that produce cryptorchidism are thought to be recessive to the normal versions of the same gene (the genes that produce normal testicular descent). Therefore, if a young male inherits a normal version of the gene (normal testicular descent gene) from one parent and a defective version of the gene (cryptorchidism gene) from the other parent, then that young animal will be a carrier of the cryptorchidism defect (it will have one copy of the defective gene to pass onto its own offspring), but it will not have undescended testicles itself. It will look normal. This is because the normal version of the gene is dominant to the defective (cryptorchid) version of the gene and will, therefore, effect normal testicular descent. Thus, it is not possible to detect whether or not an animal carries the cryptorchidism gene purely on the basis of whether it looks cryptorchid or not: the animal could be a carrier of the defective gene and show no outward signs of the defect.
The only way that a young male animal will actually display the cryptorchidism trait is if it inherits two copies of the defective gene (one from each parent). Without the presence of a dominant normal-testicular-descent gene to overpower them, the recessive cryptorchidism genes will win the day and the animal will outwardly display the cryptorchid defect. The significance of this is that in order for an obviously cryptorchid animal to be produced in a litter, both of its parents must at least be carriers of the recessive defective gene, whether or not they actually outwardly display the cryptorchid trait. (Note - fathers/sires with normal-looking testicles will probably be carriers of one copy of the defective gene and not show the trait themselves due to the presence of a single dominant copy of the normal gene. Fathers with outwardly obvious signs of cryptorchidism will most likely have two copies of the recessive defective gene in their genome (DNA) and they will therefore be guaranteed of passing the negative trait on to all of their sons and daughters - a very good reason for not breeding obviously cryptorchid males). Another significant point of this is that, if both parents carry the defective genes (enough to produce a clinically cryptorchid son), then the chances of one or both parents having passed the defective genes on to their other sons and daughters is also very high. This will result in other cryptorchidism-affected sons (siblings of the affected animal) and also in a number of not-outwardly-cryptorchid sons and daughters that have (carry) one copy of the recessive, defective gene in their genomes. This single defective gene will go unrecognised in these carrier animals (because it is recessive) and potentially be passed on to the next generation, resulting in cryptorchidism popping up all down the generational line. This is particularly so if in-breeding occurs.
Hernias What Are They
There is a lot of confusion regarding hernias, what they are, are they fixable, and how to identify them. It will help if we run over some of the different kinds of hernias and have a generalized discussion of what they are, what causes them and what their basic prognosis is.
The word, “hernia” refers to a split in the muscle wall that allows tissue from other parts of the body to come through the split. That definition is key and will help you in your assessment. OTHER BODY PARTS COME THROUGH THE OPENING IN THE MUSCLE. These hernias are located primarily in one of three areas of interest to dog breeders: 1. the umbilicus, 2. the groin or 3. the testicles. The most common for dog breeders is the herniated muscle surrounding the Umbilicus or Umbilical cord. These hernias occur in almost all species, most definitely in humans as well.
There are two types of tissue events that are referred to as umbilical hernias in puppies but only one of these “tissue events” is an actual hernia. So, let’s first eliminate the one that is not an actual hernia, requires no treatment, and is not significant at all from a health point of view. It can easily be removed for cosmetic reasons if desired, but removal is not necessary and it is viewed strictly as a removal; not a repair.The cord carries three important blood vessels that transport blood from the mom, through the placenta and into the baby’s body. Naturally there is a small, rounded hole there in the abdominal wall that allows those blood vessels to enter the baby’s body. Sometimes that naturally occurring, very small, rounded hole doesn’t close off in time and a small amount of subcutaneous fatty tissue from the abdominal wall can migrate through that little tiny but necessary little hole and get trapped between the skin and the muscle when the little hole finally seals off. This little piece of tissue is easy to identify. It is firm to the touch and when you press against it, it pops immediately back. When you gently palpate the abdominal wall, you can feel that it is sealed and you cannot place your finger well into the abdomen. When you place the puppy on its back, the little piece of firm tissue remains in place and does not sink back into the body, nor can you manipulate it to make it go back into the body when puppy is in a back lying position. This is not a true hernia, does not present a danger to the health of the puppy and does not require surgery unless you want to have it removed because you do not like the way it looks. Some of these hernias “grow” as the puppy grows and some of them do not. It depends on exactly what type of tissue got trapped between the skin and the muscle wall that will determine if it experiences growth as the puppy grows. This would ever be considered a repair, only a removal. It will not grow back and once it is removed, it is gone forever.
Some breeders feel that this little ‘tissue event’ is due to moms who are a bit too energetic while chewing the cord. Other breeders feel that there is a genetic component to the formation of these little inaccurately named ‘hernias’. There have never been any actual studies on the cause of these hernias, but it is well accepted that they occur as frequently in c-section births as in free whelps so perhaps that discounts the idea that moms cause them by chewing the cord with a bit too much enthusiasm.
The second kind of umbilical hernia is entirely different; almost the polar opposite of the first kind of ‘tissue event’ that is not an actual hernia. A true umbilical hernia is most likely genetic in nature. If you have a puppy with a true umbilical hernia, you might consider not repeating that particular breeding next time around if you feel that genetics played a role. After reading the next section, you will easily be able to discern between the two umbilical tissue events.
The wall of the abdomen sometimes splits open in the muscle around or near the umbilicus. This is a serious birth defect, must be repaired, can reoccur after it is repaired and can present a serious health risk to the puppy or adult dog at any time. This split will always be split in the direction from the head to the toe, never sideways. Portion of the intestine will protrude from the hole and can get trapped or “strangulated” leading to intestinal necrosis (dead tissue), infection and
death. It’s easy to determine the difference between the two types of hernias. When you gently palate this area, the most noticeable thing you will feel is that the stuff that is protruding from the hole in the muscle is soft…soft…soft…..so soft that you can’t imagine it until you actually feel it. Your finger can go all the way inside the puppy to the spine. The ‘feel’ of that protruding tissue is much softer by far than the texture of a water balloon. Just imagine how a water balloon feels and then imagine something 100% softer. If you place a stethoscope on that soft protrusion, you can hear the bowel sounds (sounds like when your stomach ‘growls’) clearly. If you place the puppy on its back and gently push that sooofffftttt tissue back inside the abdomen, it stays inside until the puppy gets up again. Gravity will pull the intestine back and away from the split in the muscle wall. It doesn’t pop back out. It stays inside the puppy and in that position, you can sometimes gently palpate the actual hole in the muscle wall. You can feel the perimeters of the split in the muscle fibers.
So, in review, the first kind of ‘tissue event’ is not a hernia. The muscle wall is intact behind the little lump of firm tissue. You can feel the intact muscle wall and you can feel the little scar where the hole used to be that the blood vessels traveled into the puppy’s body. When you push it into the stomach area, it pops right back out whether the puppy is on its four feet or on its back. This is not a hernia. Sometimes it grows as puppy does, sometimes not and can easily be removed for
cosmetic reasons if you desire. You can educate your puppy buyers about this little ‘tissue event’ and they can have it removed at time of spay or neuter if desired for cosmetic reasons.
The second kind of hernia has a body part (intestine) coming through it, is soft, soft, soft to the touch and would allow your finger to go well into the abdomen and stay there. This is a true hernia. If the puppy is on its back, you can push the soft tissue (intestine) back into the large sized hole and it will stay inside the body and look normal. This true hernia is much softer than a water balloon and has the sounds of a ‘stomach growling’, which are actually the sounds that intestines make all day as they digest and process food and fluids. This hernia requires surgical repair as soon as your vet feels that the puppy is old enough for the surgery.
Another hernia that dog breeders see is an inguinal hernia, which occurs in the area of the abdomen where the rear legs attach to the abdomen. Inguinal hernias in the muscle wall also occur in the head to toe direction versus side to side. It is usually a smaller hole in the muscle wall than the umbilicus hernia. It is not as common as the first type of umbilical tissue event that we discussed, but it is more common than a true umbilical hernia. If the hole in the muscle wall is large enough, a small portion of the intestine will protrude through the hole and the same assessment tool applies. If you gently palpate and push the intestine through the hole after you have placed the puppy on its back, and if the escaping tissue
(intestine) stays in perfect position, you are safe to assume that this is a true hernia. The prognosis is more varying on the inguinal hernia. If the hole is small enough, it may disappear as the puppy grows. The muscle fibers are in a head to toe arrangement and as the puppy grows in length, sometimes the growth of those long muscle fibers allow it to close and it is no longer a problem.
If it has not closed over by the time the puppy has achieved about 85% of its body growth, you should consult a vet to see if the vet recommends its surgical closure. Prior to breeding a bitch with this type of hernia, you would want to have it repaired because the pressure within the abdominal cavity that is associated with gestation could force the intestine through the hole. The presence of the full uterine horns could be severe enough that the intestine could not return to the abdomen and become ‘strangulated’, trapped and necrotic. This type of hernia is less likely to reoccur after repair but it can happen so it’s a good idea to include a brief assessment of the area during every bath.
The last type of hernia that dog breeders could conceivably see is rare in the canine because their center of gravity is different than for a human. It is not common in humans either but because it can occur suddenly and without warning in any dog of any age, I would like to bring it to your attention. You are unlikely to see it, but it can happen.
Testicular hernias occur when the muscle wall between the testicle and the abdomen has a small split that allows a portion of the intestine to travel into the scrotum. It would be evidenced by a larger, swollen look to the testicle, suddenly occurring and not particularly painful. This would require repair immediately. It would not be likely to recur.
I hope that this little discussion on hernias is helpful to you and can be useful to you when assessing…particularly the difference between a true hernia, and a mere ‘tissue event’ for lack of a better term
COEFFICIENT OF INBREEDING (COI)
Written by Sandra Hamilton
COI is the calculation of the level of inbreeding in a dog or litter. By breeding a half brother to a half sister or a grandparent to a grandchild your COI is 12.5%. A mating of parent to child or brother to sister is 25%.
Ideally, the COI of a litter should not exceed 6.25% and it is highly recommended to avoid COI’s in excess of 12.5%. A COI in excess of 20% should be totally avoided.
High COI percentages increase the possibility that genetic defects will be carried from common ancestors, on both sides of the pedigree, and will match up to cause the actual genetic disease or defect in the animal.
Many other problems of a high COI also affect dogs such as Autoimmune disease and inbreeding depression symptoms, which result in reproductive and longevity issues.
Here are some inherited diseases and faults in herding breeds:
Hip and elbow dysplasia
Eye disease such as: cataracts, Collie Eye Anomaly (CEA) and Progressive Retinal Atrophy (PRA)
Allergies and skin problems
Bad bites and missing teeth
Temperament problems, such as shyness and aggressiveness
Inbreeding depression symptoms are seen as the loss of viability or function resulting from excess inbreeding. Sometimes these symptoms are very subtle and gradual and are often blamed on diet, pollution and other environmental factors. While these factors may also contribute, it is the dogs genes that make it more susceptible.
Here are the most frequently seen inbreeding depression signs:
Chronic poor health/poor keepers
Higher incidence of disease in a line (or breed) of one or more diseases than is seen in the breed or canines as a whole
Higher incidence of immune system diseases
Unusually small litter size
Difficulty in getting bitches pregnant
Difficulty in keeping bitches pregnant
Bitches that abandon a litter or are poor mothers
Bitches that kill or damage puppies intentionally or by lack of care
Studs that are indifferent to a bitch in standing heat
Studs that can’t breed without help
Low sperm counts
Earlier average age of death in a line or in the general breed population
All of these factors make it incredibly important that you do the COI calculation on any planned litters. Keeping the breed healthy is easier than cleaning it up after the fact. Once the gene pool is closed and the genetic base remains the same, the genetic situation can either remain stable or deteriorate, it cannot improve without new genetic material brought in via outcrossing to another breed or the use of non-registered stock.
Genetic Buffering in layman’s terms is genetic traits or the ability to tell one breed from another. Genetic Drift is a “Change in allele frequencies in a population due to chance rather than selection. Please read the following link to see what these two terms mean in a breeding program.( Defining The Inuit Dog )
Inbreeding, linebreeding and the usage of popular sires are methods of the past and their time is over. I have never gone with the “popular sire” syndrome during my 30 years of breeding. Nature goes to great lengths to avoid inbreeding and so should we. COI calculations can give the breeder an indication of how inbred a dog or litter will be. Knowing this percentage will enable you to make the best choices towards reducing inbreeding in your dogs. By importing a dog you can reduce your COI but you should also be certain of what traits that dog brings into your breeding program. Breeders need to be forthcoming about problems within their lines such as temperament, gay tails, aggression, etc.. Why bother to import if you are just creating more problems within your breeding program. But we all know that breeding is a gambler’s game and the “Breeders Code of Silence” increases the stakes.
Today the emphasis should be put on health, temperament and working ability if the Collie is going to survive into the next hundred years. Active concern for health should be your number one breeding goal, because without health, you have no dog. There are DNA markers out there that should be used to decrease the propensity towards CEA, PRA, MDR1, DM (Degenerative Myelopathy), JRD (Juvenile Renal Dysplasia), Grey Collie Syndrome and a few others. By not using these tools that are available we are not helping the breed.
To correctly generate a COI you need to have all the dogs behind the pair you plan to mate for 10 generations back, as this is how far back the generations need to be taken into account. To calculate anything under 7 generations gives a false sense of security. Did you realize that one dog with 10 generations behind it has 2046 dogs in it’s pedigree. Now add the dog that you want to mate it with and you increase the COI calculation to 4092 dogs. It may seem like a lot of generations and a lot of dogs, but it is not and it is figured on a sliding scale with the generations affect reducing by the proper proportions as they recede.
As most of you know ALL AMERICAN COLLIES have English origins, and most feature a dog named English CH. Magnet (among many other imports). Many of the American Collie Families descend from a dog named Ch. Silver Ho Parader ROM, who was born in 1943. This dog was hugely important because he had physical and temperament traits that were lacking in the breed at the time. He was very prepotent for these virtues, but he was not tightly bred, so his genetic contribution was quite diverse for a single individual. The diversity introduced via bitches bred into the Parader stud dog line-up, have further broadened our gene pool here. There have also been several other “influential” sires in Parader lines to whom all the dogs in those lines trace. Ch. Twin Creeks True Grit ROM and Ch. Tartanside The Gladiator ROM, are the major two. They are followed by other founders such as Ch. Twin Oaks The Joker’s Wild, Ch. Fury’s The Spirit of Legends, Ch. Antrum Alltheway and most recently Ch. Fantasy’s Bronze Talisman ROM. We, however, must remember the extreme importance of bitches bred into stud dog lines as a source of genetic diversity. Saying that all the dogs of a breed or a major sub group within a breed come down from a single sire misses the influences of the bitches which grow exponentially with each generation. I was told that “NO NORTH AMERICAN COLLIE COULD BE TRACED BACK TO DAZZLER OF DUNSINANE”, but by tracing not only tail-male lines, but tail-female lines I could trace back quite a few of my own dogs to this Sire. It was the tail-female lines that helped, but they are still an important part of the pedigree lineage and genetic diversity.
It’s interesting that about 20% of the American Collie Families were not crossed to Parader, either at all, or much later. These are the Brandwynes, or what some Americans like to call “Fluffies”. Interestingly, the Brandwynes are what other countries, especially the UK and Brazil, prefer to import while the Parader group is the preference of Japan and China.
I have imported three dogs from overseas and give a “BIG THUMBS UP” to those breeders who recognize that genetic diversity is needed. However, I have learned that to focus on one thing means you may lose ten things along the way. You must concentrate on “the whole not the parts” when trying to get genetic diversity. When importing those three dogs (for diversity sake) they fell short of my expectations. I have followed the UK/North American breedings from my exported boys and the combinations have seemed to work, but the combo here in Canada did not meet my expectations. Since this did not work I then imported a dog from the United States that came down from UK/Brazilian lines and when bred back to my bitches produced stunning pups of promise with great genetic diversity.
Someone once told me that selection was the key to success. But you must trust the breeder to be honest with you if you can’t do a hands on evaluation to select a puppy for you. It’s better to pass on a dog/bitch than to receive disappointment.
Genetic Diversity all comes down to Breeders being TOTALLY honest about their lines and breedings, and talking truthfully with each other. Egos have no place in a breeding program!
HD (certification on hips ) Hip dysplasia
Hip dysplasia literally means an abnormality in the development of the hip joint. It is characterized by a shallow acetabulum (the "cup" of the hip joint) and changes in the shape of the femoral head (the "ball" of the hip joint). These changes may occur due to excessive laxity in the hip joint. Hip dysplasia can exist with or without clinical signs. When dogs exhibit clinical signs of this problem they usually are lame on one or both rear limbs. Severe arthritis can develop as a result of the malformation of the hip joint and this results in pain as the disease progresses. Many young dogs exhibit pain during or shortly after the growth period, often before arthritic changes appear to be present. It is not unusual for this pain to appear to disappear for several years and then to return when arthritic changes become obvious.
Dogs with hip dysplasia appear to be born with normal hips and then to develop the disease later. This has led to a lot of speculation as to the contributing factors which may be involved with this disease. This is an inherited condition, but not all dogs with the genetic tendency will develop clinical signs and the degree of hip dysplasia which develops does not always seem to correlate well with expectations based on the parent's condition. Multiple genetic factors are involved and environmental factors also play a role in determining the degree of hip dysplasia. Dogs with no genetic predisposition do not develop hip dysplasia.
At present, the strongest link to contributing factors other than genetic predisposition appears to be to rapid growth and weight gain. In a recent study done in Labrador retrievers a significant reduction in the development of clinical hip dysplasia occurred in a group of puppies fed 25% less than a control group which was allowed to eat free choice. It is likely that the laxity in the hip joints is aggravated by the rapid weight gain.
If feeding practices are altered to reduce hip dysplasia in a litter of puppies, it is probably best to use a puppy food and feed smaller quantities than to switch to an adult dog food. The calcium/phosphorous to calorie ratios in adult dog food are such that the puppy will usually end up with higher than desired total calcium or phosphorous intake by eating an adult food. This occurs because more of these foods are necessary to meet the caloric needs of puppies, even when feeding to keep the puppy thin.
If clinical signs of hip dysplasia occur in young dogs, such as lameness, difficulty standing or walking after getting up, decreased activity or a bunny-hop gait, it is often possible to help them medically or surgically. X-ray confirmation of the presence of hip dysplasia prior to treatment is necessary. There are two techniques currently used to detect hip dysplasia, the standard view used in Orthopedic Foundation for Animals (OFA) testing and X-rays (radiographs) utilizing a device to exaggerate joint laxity developed by the University of Pennsylvania Hip Improvement Program (PennHIP). The Penn Hip radiographs appear to be a better method for judging hip dysplasia early in puppies, with one study showing good predictability for hip dysplasia in puppies exhibiting joint laxity at 4 months of age, based on PennHIP radiographs.
Once a determination is made that hip dysplasia is present, a treatment plan is necessary. For dogs that exhibit clinical signs at less than a year of age, aggressive treatment may help alleviate later suffering. In the past a surgery known as a pectineal myotomy was advocated but more recent evidence suggests that it is an ineffective surgical procedure. However, administration of glycosaminoglycans (Adequan Rx) may help to decrease the severity of arthritis that develops later in life. Surgical reconstruction of the hip joint (triple pelvic osteotomy) is helpful if done during the growth stages. For puppies with clinical signs at a young age, this surgery should be strongly considered. It has a high success rate when done at the proper time.
Dogs that exhibit clinical signs after the growth phase require a different approach to treatment. It is necessary to determine if the disorder can be managed by medical treatment enough to keep the dog comfortable. If so, aspirin is probably the best choice for initial medical treatment. Aspirin/codeine combinations, phenylbutazone, glycosaminoglycosans and corticosteroids may be more beneficial or necessary for some dogs. It is important to use appropriate dosages and to monitor the progress of any dog on non-steroidal or steroidal anti-inflammatory medications due to the increased risk of side effects to these medications in dogs. If medical treatment is insufficient then surgical repair is possible.
The best surgical treatment for hip dypslasia is total hip replacement. By removing the damaged acetabulum and femoral head and replacing them with artificial joint components, pain is nearly eliminated. This procedure is expensive but it is very effective and should be the first choice for treatment of severe hip dyplasia whenever possible. In some cases, this surgery may be beyond a pet owner's financial resources. An alternative surgery is femoral head ostectomy. In this procedure, the femoral head (ball part of the hip joint) is simply removed. This eliminates most of the bone to bone contact and can reduce the pain substantially. Not all dogs do well following FHO surgery and it should be considered a clear "second choice".
Hip dysplasia may not ever be eliminated by programs designed to detect it early unless some effort is made to publish the results of diagnostic tests such as the OFA evaluation or PennHIP evaluations and in canada OVC Guelph university , openly. This is the only way that breeders will be able to tell for certain what the problems have been with hip dysplasia in a dog's ancestry.
When an older dog is exhibiting signs of pain associated with this condition it is often possible to help them dramatically through medication and simple steps like providing a warm bed or warm spot to rest during the day. There is no advantage to pain and steps should be taken to ensure that the older dog is not in pain. Regular exercise can be very helpful and weight loss can have dramatic effects on the amount of discomfort a dog experiences.
Working with your vet to come to the best solution for your dog and your situation will enable you and your dog to enjoy life to its fullest, despite the presence of hip dysplasia.
Demodectic mange is the result of Demodex canis, a microscopic mite multiplying out of control. Most dogs have demodex mites on their skin in small numbers. These mites are acquired by puppies shortly after birth, from their mother.
The causative factors as to why some dogs develope demodectic mange while other dogs do not is not fully understood. The tendancy to be suseptible to demodectic mange appears to be hereditary. It is known that dogs with demodectic mange have an immune system defect. It is this defect that appears to be inherited, making the pup unable to keep the demodex mites under control.
Demodectic mange occurs in one of two forms. The first form is the localized form. This form most often appears in dogs under 1 year of age. The first sign is a thinning of hair around the eyelids, the lips, the corners of the mouth and the front legs. The dog has a moth-eaten appearance. The patches of hair loss can progress into circles of approximately one inch in diameter (occasionally confused with ringworm). Mite removal/reduction normally consists of cleansing shampoos, antibiotic therapy, and immune stimulants. Not all young animals that experience demodicosis are immunologically impaired for life. A significant percentage will "self cure" as their immune system matures. This maturity normally takes place between the ages of 8 months and 3 years, depending on the breed of dog.
During treatment it is critical that the dog is making continuous improvement. If the animal has 5 or more patches, or is not showing a marked improvement; the demodex could be progressing into the generalized form.
The generalized form is the second presentation type of this condition. Generalized demodex can begin as a localized case or can present itself as a sudden onset. Numerous patches appear on the head, legs, and trunk. These patches continuously spread developing into large areas of hair loss. The hair follicles become congested with debris and mites. The breakdown of the skin leads to the formation of sores, with crusting and draining sinus tracts.
Treatment of dogs experiencing generalized demodex can be very prolonged. The reponse to treatment is slow and often requires frequent changes in the medication. In spite of the number of mite removal dips, topical ointments and antibiotics availale a cure is not always possible. Generalized demodectic mange must be treated under veterinary supervision.
Older dogs that develop demodectic mange (in either form) should be screened for underlying causative factors in immune system dysfunction. Diseases such as diabetes, cancer or Cushing's disease can all impact therapy.
Dogs treated for generalized demodectic mange should be neutered
Seizures occur for many reasons. There are a number of classification schemes for seizures based on why they occur or what they look like when they do occur. A short explanation of one of those schemes might help to understand what the possibilities are.
Seizures can occur for no apparent reason --- and no reason can be found despite careful examination. This type of seizure activity is referred to by some vets as primary epilepsy, or idiopathic epilepsy. Most of the time the onset of seizures in dogs with primary epilepsy is between one and five years of age and there usually is a fairly long interval between the first seizure and subsequent seizures when they occur. While primary epilepsy is common it is not the most likely problem in Eddie's case because he was older when the seizures started and because the interval between seizures was short.
Seizures can occur as a reaction to medication, allergies, toxins, other diseases, fevers and anything else that disturbs brain function. These seizures are sometimes referred to as reactive seizures or secondary seizures. It is often possible to figure out the cause of this type of seizure based on the history of another illness known to lead to seizure activity, the clinical signs at the time of seizuring or a known history of using a medication that may lead to seizure activity. Allergies are a lot harder to rule out as a cause of seizures, especially food allergies. It may be worth following an limited antigen diet. This is a diet with one meat source, preferably a meat source that the dog hasn't eaten before, and limited carbohydrate sources, such as just rice or just potatoes. I think that seizures due to allergies probably occur, based on several clinical case reports in the literature, but I think that they are pretty rare. Still, when seizures won't respond to medication it seems reasonable to rule out this possibility. Reactive seizures can occur at any age. A careful review of Eddie's prior medical history to try to rule out exposure to distemper, toxins such as lead, chronically administered medications and other illnesses can be helpful, sometimes, in discerning the cause of
Another cause of seizures is anatomical or structural disease in the brain. This can be from a brain tumor, hydrocephalus (inadequate drainage of fluid in the skull), bleeding in the brain, circulatory problems in the brain and other structural or anatomical problems. Unfortunately, in older dogs (over five years of age) with seizures that occur without a prior history of seizure activity and that recur quickly, the most likely diagnosis is a brain tumor. This means that this possibility is high in Eddie's case. Magnetic resonance imaging (MRI) and computed tomagraphy (CT) scans are very helpful in diagnosing brain tumors. Due to the cost of these procedures it may be a good idea to think about the next step for a brain tumor, which would be radiation therapy or surgery, before spending the money for the scans. If you know that these options are not available or not suitable in Eddie's case, then it may not be worth making a definite diagnosis. A really careful neurologic exam might reveal clues about the possibility of a seizure but most of the time there aren't discernible neurologic signs in dogs with brain tumors, at least early on.
The last cause of "seizures" are things that look a lot like seizures, but aren't. The most common problems that are sometimes mistaken for seizures are fainting due to heart disease and low blood sugar (hypoglycemia), which is most commonly associated with overproduction of insulin due to insulinomas (a tumor of the pancreas). I don't think these problems are very likely as it seems like your vet is being cautious about testing for them.
Potassium bromide does make a good addition to phenobarbital for seizures that are hard to control. In addition it does seem like some dogs need to be at the high end of the serum levels ( 30 to 40 ug/dl at trough times ) in order to have seizure control
Collie Puppy Skulls Evaluations
Illustration below 2 & 3 . I could go into a long detailed discussion of the "WHY'S " of this but really what you want to know is if the patient will recover .The safest rule of thumb ,and one that has worked successfully over years with many bloodlines ,is that if the TOP of the occipital bone ( Arrow -illustration lower left ) is ABOVE the line of the muzzle ,as in 2, the skull will probably level out and fill in smoothly ( Given good Inheritance ) As in 2-A. Also , if the puppy excelled in CORRECT PARALLEL PLANES of muzzle and Back Skull, And was good in stop ,around the 12-week period .as in (1 ) Below top left he has a good chance of correcting If the Occipital bone ( arrow ) is on the same plane with the line of muzzle , as in 3, then almost certainly the dog will at least have a receding skull. though it may flatten and fill in , and stop may remain bulged as in 3-A . It is all a matter of balance , stress and growth . the high occipital allows the head to grow LONG without stress, giving good flat parallel planes . while the puppies are in full bloom stage around 12 weeks , when everything is just about right ,observe with a clear eye where the STRENGTH lies. Good planes ,good stop, good balance . Where the PROBLEMS lie, because when things go wrong it is important whether it is in an area where the pup was strong or weak Illustration By Allene McKewen
Seven Foundations of a Successful Dog Breeder
written by Jonathan Jeffrey Kimes
Listed in this article are some axioms that I have created as a learning tool. These axioms are reflections of the temptations we face on a daily basis as dog breeders. If one were to make a similar list for any human endeavor, I doubt it would differ much from what I have listed. I think this list is one that we should all review from time to time, for it requires maturity and self-confidence to master - something we all should continue to hone throughout our lives. The ultimate payoff is the ability to succeed in and to enjoy our dog breeding careers.
I - ENJOY YOUR DOGS
The primary reason anyone becomes involved with dog breeding and showing is a fundamental love of dogs. We treasure the companionship, the never failing loyalty, the delight they exude. We love to have them on our beds. Their eagerness to face the new day, even when we wake them up at dreadful hours, provides us a wonderment that brings back the exuberance of childhood. They forgive us when we lose our temper, when we are impatient, when we are far less than they are. They bring out the best of ourselves, they nurture the "big" us.
Unfortunately, dog breeding and exhibiting can tempt our "little" selves. It can feed a fragile ego until it becomes a raging ego. Often, this need to feel we are better than our fellow man is expressed in our possessions. We need to have the biggest winner, the producer of the most champions, the most champion puppies. We buy, we co-own, we collect. Soon we have no time for dog pleasures, no time to play or rub a grateful belly, no time to stroke a patient brow. Soon we have no room for more dogs; we stack them and crate them and store them as though they were baubles that have no meaning but to make us feel important. We lose our ability to love. Dog showing and breeding is a great vocation. It is creative and challenging and very rewarding. But we must never expect our hobby to take the place of a psychologist's work. We must never expect an unhealthy mental state to be cured by self-indulgence. Far too many people take to showing and breeding for the wrong reasons. Their houses go to ruin, their bank accounts evaporate, their credit hits the skids, their spouses and children are left to survive on their own as the breeder pursues their own manifestation of what they perceive to prove their self-worth. Being a dog breeder is a huge commitment. It means we should assign ourselves the role of lifetime student. It means we will be humbled in countless ways and in countless circumstances. It means our lessons will be of the hard knock variety if we are to truly learn them. It means frustration, long hours, late nights and early mornings. It means never getting to sleep-in again. It means finding friendships - some of which will last for a lifetime and some of which will founder, being built on social advantage. It means being quoted and misquoted and having words put in your mouth. It means being given ample opportunity to be as "small" as a human being can be. But, hopefully, it can provide an opportunity to learn to be "big," to be generous, inquisitive, and adventurous. We should never ask ourselves if we are envied or important or successful. Those questions are meaningless. At the end of the day, we should ask ourselves, "Am I proud of the person I've become?" What we must always be are dog lovers. We must be their advocates. We must ensure the life of every dog we breed and every dog we own is fulfilled and an illustration of humanity at its finest hour. Our vanity must not be stroked by having our pictures in a magazine or seeing our name on some ranking system. Our self-worth must come from knowing we provide our dogs a life of love, of pleasure, and of happiness.
II - BREED FOR IMPROVEMENT NOT WINNERS
It is easy to become lost in the purpose of breeding quality dogs. For some, the attraction of the bright lights, the glamour and the glitz cause them to stray from the path. Developing a bloodline that is well considered and that is a positive influence for the breed takes considerable discipline. Too often, the seemingly slow and carefully orchestrated effort to improve a breed is crossed up with the immediate desire to breed that one big winner and become famous.
The breeder's pledge must be to harbor and safeguard the breed. No breed is in perfect shape when the breeder happens upon it and none shall be perfect when they leave. But to leave a breed in better shape than it was when you came upon it is the greatest compliment. To improve type, movement, temperament and health must be the bottom line for every committed breeder.
Such accomplishment takes a long-range plan that is carefully thought through. It requires dedication and purpose. All too often, we are sidetracked by our desire to breed to the latest big winner, and then to the next and the next. Before long the pedigree is a long list of "who's who" that have no relationship to each other, other than they found success in the ring. What is key to learn (and to believe) is success in the ring is not an automatic indication of the dog's true quality. We all wish one indicated the other but that is too easy. It would require the removal of human fallacy to be accomplished!
Dogs do not excel for all the same reasons. Consequently, you can't simply breed one big winner to another and produce more big winners. Every feature and their nature of inheritance must be studied and understood before you can "manage" the inheritance variables. Once you gain this skill, you are on the road to producing a great line of winners.
III - TO THINE OWN SELF BE TRUE
The breeding of fine purebred dogs should be considered the pursuit of perfection - it is not the maintenance of it. All dogs have faults, all dogs are less than ideal in some ways and areas. If not, the "ideal" has not been well enough conceived. It is very easy to fall into the trap of being defensive about one's own dogs. This usually happens because what we assume to be correct is challenged by another as being less so. This disharmony causes confusion in our mind and ultimately unhappiness. To right ourselves, we often become defensive and try to rid ourselves of that which is causing us the discomfort - namely the opinion that does not complement our own.
We must realize that "truth" is the ultimate standard by which our decisions should be made. In most cases, a roached back is a roached back, whether we choose to recognize it as such or not. Consequently, the best way for us to not be put into a position of being unhappily surprised is to pursue knowledge relentlessly to ensure our opinion is as accurate and close to the "truth" as possible.
This knowledge is gained in many ways, one of which is learning from fellow breeders. We must fight the urge to make up our minds about something and refuse to consider another viewpoint. Indeed, we do not make decisions based on facts when we are first learning; we are depending upon what we perceive to be the expertise of others to provide that for us. If that so-called expertise is, in fact, faulty our whole knowledge base is called into question. And that causes us great anxiety.
The best place to sit is in the seat of the knowledge seeker. Whenever provided with an opinion that is different than the one you currently hold always seek to understand the viewpoint of the other. Why does the person perceive something differently than you? Understanding another's point of view can be the road to greater knowledge. If you shut that door and do not entertain the prospect of learning something different than what you think is truth you will never actually recognize the truth and you will not succeed in your goal.
Quite honestly, you should be more critical of your dogs than anyone else could possibly be. That is not to say you should attribute faults to your dogs they do not possess, but your evaluation must be as detailed as possible and you must strive to see clearly their true faults and virtues. From this comes the map to success.
IV - DEAL WITH OTHERS AS YOU WOULD HAVE THEM DEAL WITH YOU
Sounds a bit like the golden rule that we learn in childhood. Yet it is amazing how many people forget this very important axiom. In dealing with others, regardless of the matter, think always of the other person's position. I have heard repeatedly people state how they were burned in a co-ownership agreement. All too often the agreement is geared toward benefitting one party (often the seller) over another. Written agreements somehow are tainted as being only needed in a contentious situation. This is the first misconception. Not having a written agreement should be the very rare exception, not the reverse. Too often should a worthwhile puppy be produced from one of these undefined arrangements, the fight is on for possession. Before contemplating selling a dog on a co-ownership or leasing it or offering stud service for a puppy back you should think through what exactly you expect and desire from such an arrangement. Too often these business dealings occur in the spur of the moment during a telephone conversation, and the deal is struck before either party has really had an opportunity to think it through. For some reason rather than rethinking the situation, we tend to try to follow through on such an ill conceived arrangement only to end up bitter enemies in the end. If people would stop and think about the likely end result they would realize the best possible thing to protect the friendship is to have a written understanding.
It is very rare a litter is going to have more than one star if any at all. Consequently, it is important to understand who is going to own that super puppy, should it appear. People are too willing to tear apart relationships should one person seem to benefit a bit more than another. This is too sad and is reflective of the self-benefit motivation that all too many find as the driving force for their actions. When pressed, it is far better to give than to receive. It is far better to let the other seemingly benefit than to destroy a relationship and acquire the reputation of being disreputable and self centered, if for no other reason than it makes you grow as a human being, which is probably a fair trade off in the long run.
V - BY GIVING YOU HAVE NOTHING TO LOSE
Another pitfall breeders often experience is the inability to celebrate other's successes. While certainly we feel the route we are taking is the best way to approach that utopian plateau of breed perfection, there are actually many routes to that same goal. It takes nothing at all away from our own accomplishments to recognize the accomplished efforts of other breeders.
This inability and unwillingness to appreciate other's efforts usually comes from having made a decision not to breed to certain bloodlines or deal with certain persons. When such a kennel then produces a success, it is difficult for us to acknowledge such an achievement for we tend to find that inconsistent with our opinion of that particular person or family of dogs. It takes quite an honest and secure person to recognize and celebrate the accomplishments of others.
While it is probably good advice to hold our criticisms closer to our chest, recognizing another's achievement only brings good things. By being someone who can see the virtues in breeding lines other than your own, you gain a reputation of fairness and objectivity that is a very rare pearl in dogdom. You may find, over time, that your point of view and your philosophies are taken with much greater weight when others do not perceive them to have originated in a mind consumed with self-aggrandizement. Thus, by doing so you lose nothing and yet you gain so very much.
VI - MAKE USE OF OTHERS' ACHIEVEMENTS
One of the worst situations a breeder can find her/ himself in is to partition themselves off from another kennel or bloodline. It is highly unlikely that all improvements toward the perfection of a breed are going to come from one single kennel or bloodline. Like flowers in the field, they will spring up in various places. The clever breeder is the one who knows how to pick from all the field those who will make the ultimate, sublime bouquet. And to do this, you must be able to use the strengths of other kennels and bloodlines. Breeders will tend to have certain biases; and quite honestly, there are certain strengths and weaknesses in most bloodlines. While you may feel you have achieved the highest ground in certain areas, there will doubtless be other areas in which your dogs and bloodlines are less strong than others. Not to recognize this fact is to ensure you will plateau quite early in your breeding career. And by that I mean you will stabilize and go no further. You must always keep a watchful eye for that very special bloom that will enhance your bouquet.
It is this sophisticated combining of families without losing the good points of your own bloodline that strengthen a kennel and move it forward in breed importance. It takes careful consideration, orchestration and pruning to come to fruition.
VII - YOU ARE ONLY AS GOOD AS YOUR MORALS
My last axiom addresses the whole issue of morality. It has many facets and many ways of expressing itself. Spreading rumors, the accuracy of which might be doubtful, is one very good example. Selling dogs on co-ownerships as a means to control other breeders is certainly another. Accusing other lines of genetic problems while being less than entirely honest about your own is yet another. In all, it goes to the very core of who we are. Do we know right from wrong? Do we practice right in all circumstances? Dog breeding is not about that one great win or that one great winner. It is about breed improvement over time, it is about protecting a breed. Too many people are in search of some kind of sign of their self-worth and they think they will obtain some special level of respect and honor if they have a big winner. Dog breeding is a lifetime's work. It is a continuum of which, no matter how quickly you want to "put yourself on the map," will ultimately be a reflection of your true character. To wit, you can't fool all of the people all of the time.
There is no honor in "adjusting" reality to give you the appearance of achieving something you have not. Politicking for wins will not make your dogs any better than they are. Faking your dogs will not make them any better than they are. You may think you can fool the world, but you will ultimately pay the price. No one wants to be a pretender. And yet, some of the worst pretenders are people who seem to be infatuated with spreading rumors about other people and dogs. These people live in glass houses and invariably they know it. The breeding of dogs is not about how you impress the neighbors, your peers or anyone else. It is the expression of your love of dogs and your personal pursuit in creating an art. You cannot lie about the art you create; you cannot lie to yourself.
While this list, I am quite sure, sounds like a sermon from the mount, it encompasses the many pitfalls that we dog breeders face every day. Some of us are equipped to navigate these disturbances better than others, but all of us CAN navigate them. We are all tested from time to time, even the most educated, psychologically balanced, intelligent and honest amongst us. There are times when it feels much better to zing someone who has been hurtful, to control those whom we feel do not have the proper motivation, to become the ones who attract the adulation. Only through careful thought and well-considered action can we hope to become better people and therefore better dog breeders.
On Left Choroidal Hypoplasia on Right A Coloboma
The symptoms and signs – the clinical phenotype – can vary greatly among affected dogs within one breed, between parent and offspring and even within a litter. This creates a difficult situation for the breeder. Learning about the genetic cause and the course of the disease will help you understand how to manage it better and eventually avoid it altogether with genetic testing.
The primary problem is choroidal hypoplasia (CH). There is under-development (hypoplasia) of the eye tissue layer called the choroid. The choroid appears pale and thin, almost transparent, and the blood vessels of the choroid can easily be recognized in those “thin” areas. The ophthalmologist, looking at the back of the eye (the fundus) with an ophthalmoscope, typically will see an area of choroidal thinning that appears like a “window” to the underlying vessels and sclera.MILD disease: Mild disease is very common in U.S. collies . It is easily recognizable on careful ophthalmologic examination as early as 5 to 8 weeks of age. The lesion appears as an area lateral (temporal) to the optic disc with reduction or absence of pigment so that the underlying vessels of the choroid are seen. The choroidal vessels may be reduced in number and of abnormal shape. The underlying white sclera might also be visible. Once the retina changes to its adult color around 3 months of age, the normal pigment sometimes masks the changes in the choroid (so-called “go normal” – read more below). In mildly affected dogs, choroidal thinning is the only detectable abnormality and the dog retains normal vision throughout life. However, dogs with mild disease can produce severely affected offspring.
SEVERE disease: In severely affected dogs, approximately 25% of dogs with CEA/CH, there are related problems with the health of the eye that can result in serious vision loss in some cases. Colobomas are seen at and near the optic nerve head as outpouchings or “pits” in the eye tissue layers. Colobomas can lead to secondary complications such as partial or complete retinal detachments and/or growth of new but abnormal blood vessels with hemorrhage – bleeding inside the eye. This happens in 5-10% of dogs with CEA/CH, generally by 2 years of age, and can affect either one or both eyes. Complications of severe disease can lead to vision loss, although this disorder only rarely threatens total blindness.
CEA/CH is not progressive in the usual sense. The essential features, choroidal hypoplasia and coloboma, are congenital – the abnormalities develop as the eye develops. These features are also stationary once ocular development is complete around 8-12 weeks of life. Retinal detachments and/or aberrant vessel formation can be congenital or develop later, in general only in eyes with colobomas.
Based on research done jointly by scientists at Cornell University and at The Fred Hutchinson Cancer Research Center, BOTH the mild and severe forms of CEA/CH disease now are proven to result from the exact same gene and mutation . This disease gene is located on canine chromosome number 37 and the disease-causing mutation has been identified. The mutation acts like a RECESSIVE mutation. That means, both parents of an affected dog must have at least one copy of the mutation and both parents must have passed a copy of the mutation to the offspring. The affected dog is HOMOZYGOUS RECESSIVE – that is, both copies of the gene are mutant. ALL dogs that are homozygous recessive affected will show at least the mild form of the disease. ALL affected dogs, regardless of the actual severity of the lesions, are homozygous for the same mutant gene.
(A dog with one mutant copy and one normal copy of the CEA/CH gene is a carrier – is heterozygous. A dog with two copies of the normal CEA/CH gene is homozygous normal.)