Disease Definitions
Dogs
Myotonia Congenita
Myotonia Congenita is a disease that is inherited as an autosomal recessive mutation in the canine chloride channel skeletal muscle gene. The gene codes for specific proteins in muscles. When a mutation occurs in the gene, the nature of the amino acid building blocks of specific proteins is modified. Thus, these changes affect the ability of muscles to quickly relax after a voluntary contraction. The delay in skeletal muscle relaxation is not accompanied by cramping or pain to the animal. Affected dogs often have a rigid gate, probably due to excessive growth of the muscles. However, after exercise, the gate improves. The animals may also have an abnormal bark, and superfluous salivation with difficulty in swallowing, There is no known cure for the disorder
Clinical Signs:
- Muscle stiffness that partially resolves with exercise.
- Increase in muscle stiffness in response to any rapid change in posture.
- Abnormal upper respiratory sounds especially when beginning to move.
- Regurgitation that may occur when eating.
- Protrusion of the tongue from the mouth at rest.
- Compression of the tongue resulting in dimpling that persists for up to 30 seconds.
- Diffuse skeletal muscle hypertrophy.
- Shortening of the lower jaw (mandible).
- Electromyographic (EMG) evidence of myotonic discharges of approximately 40 seconds duration.
- Breeds most often seen with this ailment are the Miniature Schnauzer.
Reference: Rhodes, T. H., Vite, C. H., Giger, U. et al. 1999. A missense mutation in canine C1C-1 causes recessive myotonia congenita in the dog, FEBS Lett., Vol. 456, pp. 54-58.
Progressive Retinal Atrophy
Progressive retinal atrophy, or PRA as it is frequently termed, is a hereditary form of macular degeneration that results in progressive and irremediable loss of visual. In its simplest from, PRA is a disease of the retina. This tissue, located inside the back of the eye, contains specialized cells called photoreceptors that absorb the light focused on them by the eye’s lens, and converts that light, through a series of chemical reactions into electrical nerve signals. The nerve signals from the retina are passed by the optic nerve to the brain where they are perceived as vision. The retinal photoreceptors are specialized into rods, for vision in dim light (night vision), and cones for vision in bright light (day and color vision). PRA usually affects the rods initially, and then the cones in later stages of the disease. In human families, the diseases equivalent to PRA (in dogs) are termed retinitis pigmentosa.
The disease is inherited in an autosomal recessive mode.
Different types of PRA are found in different breeds of dogs.
TEST 2-A The SNP in the gene detected in this test is generally for the Cardigan Welsh Corgi.
TEST 2-B The SNP in the gene detected in this test is generally for the English Mastiff.
TEST 2-C The SNP in the gene detected in this test is generally for the Irish Setter.
NOTE: Although the PRA tests offered by Pawsitive I.D. detect defective genes
in the above referenced breeds (Test A, B & C), other breeds as noted below can
also be screened as well.
Many breeds are affected by one or sometimes more than one form of PRA.
Generalized PRA - early onset: Cardigan Welsh Corgi, Collie (rod-cone dysplasia type II), Cairn Terrier, Gordon Setter, Great Dane, Irish Setter (rod-cone dysplasia type I), Miniature Schnauzer (photoreceptor dysplasia), Norwegian Elkhound (rod dysplasia, also early retinal degeneration), Tibetan Terrier (progressive rod degeneration causing night blindness only)
Alaskan Malamute - progressive cone degeneration causing hemeralopia (day blindness) - this condition occurs rarely.
Generalized PRA (progressive rod-cone degeneration) - later onset (usually older than 1 year): Akita, Australian Cattle Dog, Australian Shepherd, American and English Cocker Spaniel, Basenji, Beagle, Belgian Sheepdog, Briard, Brittany Spaniel, Chesapeake Bay Retriever, Collie (rough and smooth), Dachshund, English Springer Spaniel, German Shepherd, German Short-Haired Pointer, Golden Retriever, Greyhound (without typical initial night blindness), Irish Setter, Labrador Retriever, Mastiff, Nova Scotia Duck Tolling Retriever, Old English Sheepdog, Papillon, Pekingese, Poodle (miniature and toy), Portuguese Water Dog, Rottweiler, Samoyed, Shetland Sheepdog, Shih Tzu, Siberian Husky, Tibetan Spaniel, Tibetan Terrier, Welsh Springer Spaniel, Yorkshire Terrier
Central PRA - retinal pigment epithelial dystrophy (RPED): This disease occurs mostly in dogs in the United Kingdom, of the following breeds: Border Collie, Cardigan Welsh Corgi, English Cocker Spaniel, English Springer Spaniel, Golden Retriever, Labrador Retriever, Rough and Smooth Collie, Shetland Sheepdog
Retinal degeneration in the Borzoi: Unlike other forms of PRA, the eyes are affected asymmetrically and the retinal lesions appear inflammatory. Males are affected more often than females. Ultimately, the ophthalmoscopic lesions are similar to those of PRA.
References:
Suber ML, Pittler SJ, Qin N, Wright GC, Holcombe V, Lee RH, Craft CM, Lolley N, Baehr W, Hurwitz RL. 1993. Irish setter dogs affected with rod/cone dysplasia contain a nonsense mutation in the rod cGMP phosphodiesterase β-subunit
gene. PNAS USA 90:3968-3972.
Ray K, Baldwin VJ, Acland GM, Blanton SH, Aguirre GD. 1994. Cosegregation of codon 807 mutation of the canine rod cGMP phosphodiesterase β gene and
rcd1. Inv Ophthalmol Vis Sci 35(13):4291-4299.
Petersen–Jones S.M., Entz, D.D. and Sargan, D. R. 1999. cGMP Phosphodiesterase-
Mutation Causes Progressive Retinal Atrophy in the Cardigan Welsh Corgi Dog. Investigative Ophthalmology and Visual Science. 40:1637-1644.
Kijas, J.W., Miller, B.J., Pearce-Kelling, S.E., Aguirre, G.D., and Acland, G.M. 2003. Canine Models of Ocular Disease: Outcross Breedings Define a Dominant Disorder Present in the English Mastiff and Bull Mastiff Dog Breeds. J. Heredity 94: 27-30.
Congenital Hypothyroidism With Goiter
Hypothyroidism refers to any state in which thyroid hormone production is below normal. Thyroid hormones have an effect on virtually every organ system in the body. There are many disorders that result in hypothyroidism. The disease is transmitted as an autosomal recessive gene. The genetic or congenital hypothyroidism may exist in a carrier state in as many as 30% of normal Toy Fox Terriers. About 1 in 4 members of a litter are affected if both parents are carriers.
Symptoms of the disease usually are manifest as lethargy, mental dullness, inadequate wound healing, inferior skin and hair coat, including hair loss, increased appetite leading to obesity, cold intolerance (pups try to find warm places), or altered pigmentation. A lump (goiter) in the neck increases with age, even with treatment. The normal process of bone lengthening is delayed and is seen in the spine, legs and muzzle. Usually, affected animals die by the age of 3 or 4 weeks.
Treatment in standard cases of hypothyroidism consists by supplementing the daily diet with a thyroid hormone called L-thyroxine. However, treatment for congenital hypothyroidism in Toy Fox Terriers is usually not pursued because it is not worthwhile.
Congenital hypothyroidism has also been reported in several breeds, including Scottish Deerhounds, Bullmastiffs, Boxers, German Shepherds, and Giant Schnauzers. It has also been seen in crossbreeds.
Reference:
Dixon, R. 2001. Recent developments in the diagnosis of canine hypothyroidism In Practice 23: 328-335
Canine Leukocyte Adhesion Deficiency
Canine Leukocyte Adhesion Deficiency (CLAD) is rare but fatal disease inherited as an autosomal recessive trait. CLAD is an abnormality of the immune system where the white blood cells are unable to fight infection. Animals that are affected display early and serious infections and usually die early in life. This disease was first identified in 1975 in Irish Setters. Several animals displaying various forms of recurrent infectious and immunological complications were found to have an aberrant expression of the CD18 molecule.
The identification of a single nucleotide polymorphism (SNP) gene mutation responsible for the disease in Irish Setters has been determined by mutational analysis of CD18 in Irish Setter CLAD pedigrees. This single missense mutation showed complete association with CLAD in Irish Setters. This mutation is thought to be responsible for incomplete disulphide bonding within the ß-integrin protein, causing defects in its function and hence impaired immune function.
Reference:
Jobling AI, Ryan J, Augusteyn RC. 2003. The frequency of the canine leukocyte adhesion deficiency (CLAD) allele within the Irish Setter population of Australia. Aust Vet J. 81(12):763-5
Neuronal Ceroid Lipofuscinosis
Neuronal Ceroid Lipofuscinoses NCL, (also known as Batten Disease) is the general name for a family of at least eight genetically separate neurodegenerative disorders that result from excessive accumulation of fats and proteins known as lipopigments in the body's tissues. The lipopigments build up in cells of the brain and the eye as well as in skin, muscle, and many other tissues and assume a greenish-yellow color when viewed under ultraviolet light. The end result is a progressive neurological disease including blindness. At the present, there is no known cure. This disease manifests itself as a progressive dementia that resembles Alzheimer’s symptoms. For example, some animals exhibit aggressive behavior, confusion, and problems adapting to environmental changes
This disease is generally inherited as an autosomal recessive gene.
TEST 5-A
SNP test CLN 2 is primarily found in Dachshunds.
TEST 5-B
SNP test CLN 8 is primarily found in English Setters. In setters, motor irregularities are observed as the disease progresses. Additionally, hyperactivity followed by violent behavior occurs when the animal is 15 to 24 months old. Most likely, death occurs by the time the dog is around three years old.
TEST 5-C
SNP test CLN 5 is primarily found in Border Collies. In Collies, motor irregularities are observed as the disease progresses. Additionally, hyperactivity followed by violent behavior occurs when the animal is 15 to 24 months old.
Reference:
Drögemüller, C., Wöhlke, A., and Distl, O. 2005. Characterization of Candidate Genes for Neuronal Ceroid Lipofuscinosis in Dog. Journal of Heredity 96(7):735-738
Cystinuria
Cystinuria is a disorder characterized by stones in the kidney, ureter, and bladder. It is caused by excessive excretion of certain amino acids (protein building blocks – specifically cystine, lysine, arginine and ornithine) due to a genetic abnormality that affects the renal tubular transport of these compounds.
The filtering action of the kidney fails to remove the excessive amino acids and they tend to form crystals, or stones, in the urine. These stones can block the urethra, especially in males, and impede the urinary stream. It generally takes a few years for the symptoms to appear.
The disease is inherited as an autosomal recessive gene.
The SNP test is primarily for the Newfoundland dog breed.
Reference:
Henthorn PS, Liu J, Gidalevich T, Fang J, Casal ML, Patterson DF, Giger U. 2000. Canine cystinuria: polymorphism in the canine SLC3A1 gene and identification of a nonsense mutation in cystinuric Newfoundland dogs. Hum Genet 107: 295-303.
Narcolepsy
Narcolepsy is a chronic, neurological sleep disorder characterized by uncontrollable sleep attacks that result in excessive sleepiness. These sleep attacks usually occur multiple times a day even when an animal gets adequate sleep. Other symptoms include sleep paralysis, cataplexy, and hypnologic hallucinations.
The disease gene is inherited as an autosomal recessive mode.
The SNP test for this disease is primarily found in the Dachshund breed although it may target the same disease in Doberman Pinschers, Poodles and Labrador Retrievers
Reference:
Marcel Hungs, Jun Fan, Ling Lin, Xiaoyan Lin, Richard A. Maki and Emmanuel Mignot. 2001. Hypocretin (Orexin) Genes of Narcoleptic Canines: Identification and Functional Analysis of Mutations in the Hypocretin (Orexin) Genes of Narcoleptic Canines. Genome Res. 11: 531-539
Muscular Dystrophy
Canine Muscular dystrophy is a broad term that describes a inherited disorder of the muscles. The most common form of MD is called Duchenne muscular dystrophy (DMD). MD causes the muscles in the body to become very weak with degeneration and sporadic contractures. The muscles ultimately break down and are replaced with fatty deposits. When a mutation occurs in the dystrophin gene, the one that codes for a muscle cell membrane protein called dystrophin, the disruption causes a break in the mechanical links that work together to stabilize the muscle. This gene is located on the X chromosome.
Clinical signs first appear at 6-9 weeks of age in the form of weakness and atrophy of the muscles. However, an early diagnostic can be administered as early as 2 days of age. A blood sample is taken and serum creatine kinase (CK) levels are checked for strikingly elevated values. Likewise, a Single Nucleotide Polymorphism (SNP) test can be used to identify dogs that carry the mutant X chromosome.
This disease is inherited in an X-linked mode and is primarily found in the Golden Retriever.
References:
Brumitt, J. W., Essman, S. C., Kornegay, J. N., Graham, J. P., Weber, W. J. & Berry, C. R. 2006. Radiographic Features of Golden Retriever Muscular Dystrophy. Veterinary Radiology & Ultrasound 47 (6), 574-580.
Kornegay, J.N., Tuler S.M., Miller D.M. et al. 1998. Muscular dystrophy in a litter of Golden retriever dogs. Muscle and Nerve, New York, v.11, n.10, p.1056-1064.
Nguyen, F., Cherel, Y., Guigand, L., Goubault-Leroux, I., Wyers, M. 2002. Muscle lesions associated with dystrophin deficiency in neonatal golden retriever puppies, Journal of Comparative Pathology 126:100-108.
Valentine, B.A., Cooper, B.J., Cummings, J.F., Delahunta, A. 1990. Canine X-Linked Muscular Dystrophy - Morphologic Lesions, Journal of the Neurological Sciences 97:1-23.
Globoid Cell Leucodystrophy
This disease is often called Krabbe disease (also known as globoid cell leukodystrophy or galactosylceramide lipidosis or GCL) and is a rare, often fatal degenerative disorder that affects the brain and nervous system. As part of a group of disorders known as leukodystrophies, Krabbe disease results from the imperfect growth and development of myelin. GCL disease is caused by mutations in the GALC gene, which causes a deficiency of a critical enzyme. The official name of the GALC gene is “galactosylceramidase but is often called galactocerebroside -galactosidase. The buildup of undigested fats affects the growth of the nerve’s protective myelin sheath (the covering that insulates many nerves) and causes severe degeneration of mental and motor skills.
The disease is manifest as general muscle weakness, awkward gait, lack of coordination, deficiency of hindquarter control and tail tremors.
The disease is most often found in West Highland White and Cairn Terriers
This condition is inherited as an autosomal recessive pattern.
Reference:
Cozzi F, Vite CH, Wenger DA, Victoria T, Haskins ME. 1998. MRI and electrophysiological abnormalities in a case of canine globoid cell leucodystrophy. J Sm Anim Prac 39: 401-405
Von Willebrand Disease
Von Willebrand Disease (vWD) is a common genetic bleeding disorder that can occur in dogs. In fact, it is not a single disease, but a family of related diseases of variable severity. All the different types in humans and in dogs are caused by a problem with the Von Willebrand Factor (vWF). This is a protein in blood which is necessary for proper blood coagulation, or clotting. When there is not enough of the protein in the blood, bleeding can be uncontrolled and sometimes life threatening. Symptoms can include undue bleeding of the umbilical cord at birth, extended bleeding at the time of tail docking, blood in the urine, or swelling in various body parts. Not all animals show clinical symptoms
The disease is inherited in an autosomal recessive mode.
Different types of vWD are found in different breeds of dogs.
TEST 10-A The SNP gene detected in this test is generally for the German Shorthaired Pointer breed.
TEST 10-B The SNP gene detected in this test is generally for the Dutch Kooiker breed and is of the Type III von Willebrand Disease.
TEST 10-C The SNP gene detected in this test is generally for the Scottish Terrier, Doberman, Shetland Sheepdog, Manchester Terrier and Poodle breeds.
Different types of vWD are found in different breeds of dogs. The SNP gene detected in this test is generally for the Scottish Terrier.
Reference:
van Dongen AM, van Leeuwen M, Slappendel RJ. 2001. Canine von Willebrand's disease type 2 in German wirehair pointers in the Netherlands. Vet Rec. 148(3):80-2.
Slappendel RJ, Beijer EG, van Leeuwen M. 1998. Type III von Willebrand's disease in Dutch kooiker dogs. Vet Q. 20(3):93-7.
Venta PJ, Li J, Yuzbasiyan-Gurkan V, Brewer GJ, Schall WD. 2000. Mutation causing von Willebrand's disease in Scottish Terriers. J Vet Intern Med. 14(1):10-9.
Gangliosidosis
GM1 gangliosidosis is a genetic lipid storage disorder that is similar in certain respects to Hurler syndrome and Tay-Sachs disease in humans. GM1 gangliosidosis is one of the classic lipid storage diseases. It affects both the brain and the viscera (the internal organs) of the dog. GM1 gangliosidosis causes skeletal deformities and imparts severe effects on the brain and internal organs. Death usually occurs by the age of 2. The gene responsible for it maps to chromosome 23 in the dog. There is no treatment for the disease. It is also known as familial neurovisceral lipidosis or Landing disease in the human.
The disease is inherited in an autosomal recessive mode.
Different types of PRA are found in different breeds of dogs.
TEST 11-A The SNP gene detected in this test is generally for the Portuguese Water Dog.
TEST 11-B The SNP gene detected in this test is generally for the Shiba Inu breed..
Reference:
Wang, Z. H.; Zeng, B.; Shibuya, H.; Johnson, G. S.; Alroy, J.; Pastores, G. M.; Raghavan, S.; Kolodny, E. H. 2000. Isolation and characterization of the normal canine beta-galactosidase gene and its mutation in a dog model of GM1-gangliosidosis. J. Inherit. Metab. Dis. 23: 593-606, 2000.
Yamato O, Ochiai K, Masuoka Y, Hayashida E, Tajima M, Omae S, Iijima M, Umemura T, Maede Y. 2000. GM1 gangliosidosis in shiba dogs. Vet Rec. 146(17):493-6.
Mucopolysaccharidosis Type VII [Dogs]
MPS VII is one of the least common forms of the mucopolysaccharidoses. The disorder is caused by deficiency of the enzyme beta-glucuronidase (GUSB). In its rarest form MPS VII causes puppies to be born with hydrops fetalis, in which extreme amounts of fluid are retained in the body. Neurological symptoms may include mild to moderate mental retardation, communicating hydrocephalus, nerve entrapment, corneal clouding, and some loss of peripheral and night vision. Other symptoms include short stature, some skeletal irregularities, joint stiffness and restricted movement, and umbilical and/or inguinal hernias.
The disease is inherited as an autosomal recessive lysosomal storage disorder.
The SNP test for this disease is directed to the gene that codes for the enzyme b-glucuronidase. Dog breeds most affected by this disorder are the German Shepard as well as many types of Mixed Breed dogs. Many cat breeds affected by Type VI & VI MILD.
References:
Ponder, K. P., Melniczek, J. R., Xu, L. et al. 2002. Therapeutic neonatal hepatic gene therapy in mucopolysaccharidosis VII dogs. Proc. Natl. Acad. Sci. USA, Vol. 99:13102–13107.
Ray J, Scarpino V, Laing C, Haskins ME. 1999. Biochemical basis of the beta-glucuronidase gene defect causing canine mucopolysaccharidosis VII. J Hered. 90(1):119-23.
Hemophilia B
Hemophilia B is a hereditary blood coagulation disorder. It is caused by a deficiency of a blood plasma protein called factor IX that affects the clotting property of blood. Dogs that have this disorder bleed very easily, as after customary vaccinations. They often have bloody diarrhea and/or lameness.
The disease is inherited as X-linked, meaning that the male dog (carries a Y and an X chromosome) is either clear or affected – he cannot be a carrier. However, the female dog carries two X chromosomes and can be homozygous for the disease on both X chromosomes and thus, affected; or she can carry the disease on one X chromosome and show no clinical signs; or can be clear of the disease and have no point mutations that code for the disease on the X chromosomes.
The disorder does not appear to be breed specific although it is frequently found in the Labrador Retriever, Lhasa Apso, and various terriers.
References:
Chao, H.J., Walsh, C.E. 1999. Endogenous canine FIX antigen exists in Chapel Hill strain hemophilia B canine. Thrombosis & Haemostasis 82:1378.
Gu, W.K., Brooks, M., Catalfamo, J., Ray, J., Ray, K. 1999. Two distinct mutations cause severe hemophilia B in two unrelated canine pedigrees, Thrombosis & Haemostasis 82:1270-1275.
Phosphofructokinase Deficiency
Phosphofructokinase Deficiency is a genetic disorder that interferes with the ability of muscles to use carbohydrates (such as glucose) for energy. It is also known as Tarui's Disease. The SNP detected in the test codes for an enzyme known as PFK (Phosphofructokinase). This enzyme is critical for energy production from sugar supplies in all cells of the body, especially muscle and red blood cells. A major symptom of the disease is muscle pain during intense exercise. Other disease symptoms are signs of discolored or darker urine, muscle weakness and cramps, anemia, and exercise intolerance. The term PFK refers to similar disorders that appear in both humans and some other mammals, especially dogs. There are no apparent successful treatments for the disorder.
Up to 10 percent of American Cocker Spaniels have been observed to have this disease. It has also been seen in English Springer Spaniels, although no breed is entirely free of the disease.
The disease is inherited in an autosomal recessive mode.
Reference:
Smith, B.F., Stedman, H., Rajpurohit, Y., Henthorn, P.S., Wolfe, J. H., Patterson, D. F., and Giger, U. 1996. Molecular Basis of Canine Muscle Type Phosphofructokinase Deficiency. J. Biol. Chem. 271 (33): 20070-20074.
Severe Combined Immunodeficiency Disease
Severe combined immunodeficiency, or SCID, is a genetic disorder in which both B cells and T cells of the adaptive immune system are crippled, due to a defect in one of several possible genes. SCID is a severe form of heritable immunodeficiency. It is also known as the "bubble boy" disease because its victims are extremely vulnerable to infectious diseases and must be kept isolated from others.
The disease is transmitted in an X-linked recessive pattern. Thus, only males are affected and show symptoms of the disease. As in other X-linked genetic diseases, females may be carriers of the trait. Therefore, one-half of her male puppies will have the disease gene.
After weaning, and thus being deprived of the mother’s immunoprotective milk, pups become afflicted with physical problems such as respiratory infections, ear and skin infections and diarrhea. None of these conditions responds well to antibiotic therapy. There is no known cure for this disease.
TEST 15-A The SNP test for this gene is primarily found in the Cardigan Welsh Terrier.
TEST 15-B The SNP test for this gene is primarily found in the Basset Hound.
TEST 15-C The SNP test for this gene is primarily found in the Jack Russell Terrier.
References:
Felsburg, P.J. 1992. Primary immunodeficiencies. In J.D. Bonagura and R.W. Kirk (eds) Kirk's Current Veterinary Therapy XI Small Animal Practice p. 448-453. W.B. Saunders Co., Toronto.
Henthorn, P. S., Somberg, R.L. Fimiani, V.M., Puck, J.M., Patterson, D.F. Felsburg, P.J. 1994. IL-2R gamma gene microdeletion demonstrates that canine X-linked severe combined immunodeficiency is a homologue of the human disease. Genomics 23(1), 69–74.
Bell, T.G., Butler K.L, Sill, H.B., Stickle, J. E., Ramos-Vara, J.A., Dark, M. J. 2002. Autosomal recessive severe combined immunodeficiency of Jack Russell Terriers. J Vet Diagn Invest 14:194–204
Thrombasthenic Thrombopathia
Thrombopathia means a disorder of small blood cells called platelets or thrombocytes. Platelets play an important role at several stages of the body's response to any injury that causes bleeding. One function of platelets is to aggregate or "clump" at the site of blood vessel injury to form an initial plug. Platelets also facilitate blood clotting, in conjunction with the clotting factors, and release substances active in inflammation and tissue repair. Affected animals have lengthened times of bleeding after injury or blood drawing. The animals often develop deep bruises at the site of an injury.
The SNP test for this disorder detects changes in the gene that codes for a glycoprotein that is part of the platelet. There is no explicit procedure to treat this disorder. However, plasma from normal donor dogs can help acute bleeding. Also, if the animal is anemic, a transfusion of whole blood may be given.
The disease is most often seen in Otterhounds, although it has been detected in the Great Pyrenees breed.
This disease is inherited in an autosomal recessive mode.
Reference:
Boudreaux MK and Catalfamo JL. 2001. Molecular and genetic basis for thrombasthenic thrombopathia in Otterhounds. Am J Vet Res 62(11):1797-1804.
Cone Degeneration
Cone Degeneration (CD) disease causes day blindness due to degeneration of the retinal “cones” – cone-shaped cells in the retina that respond primarily to bright daylight. CD can be diagnosed in the early weeks of the German Shorthaired Pointer’s life. Between 8 and 12 weeks of age, when retinal development is normally completed in dogs, signs of vision problems are noticeable. The pups become day-blind and are photophobic – meaning that exposure to bright light is irritating or even painful. The pup will shun brightly-lit areas. Vision in dim light remains normal, in contrast to PRA affected dogs which is the more common type of retinal disease. The retina of the affected dog initially appears normal when examined by an ophthalmologist and initially the ERG (electroretinogram) recording is normal. However, the ERG response from the degenerating cones declines with age and is non-recordable in the mature CD-affected dog. There is no treatment or cure available for either canine or human disease.
The disease is autosomal recessively inherited
The dog most affected by CNGB is the German Shorthaired Pointer.
References:
Aguirre G.D., Rubin L.F. 1977. Postnatal development of the retina in Alaskan malamute dogs with inherited cone degeneration. Proc Am Coll Vet Ophthalmol 8:51.
Akhmedov, N.B., Piriev, N.I., Ray, K., Acland, G.M., Aguirre, G.D. and
Farber, D.B. 1997. Structure and analysis of the transducin beta3-subunit
gene, a candidate for inherited cone degeneration (cd ) in the dog. Gene,
194, 47–56.
Akhmedov, N.B., Piriev, N.I. 1998. Pearce-Kelling, S., Acland, G.M., Aguirre,
G.D. and Farber, D.B. Canine cone transducin-gamma gene and cone
degeneration in the cd dog. Invest. Ophthalmol. Vis. Sci., 39, 1775–1781.
Sidjanin DJ, Lowe JK, McElwee JL, Milne BS, Phippen TM, Sargan DR, Aguirre GD, Acland GM, Ostrander EA. 2002. Canine CNGB3 mutations establish cone degeneration as orthologous to the human achromatopsia locus ACHM3. Hum Mol Genet 11(16):1823-1833.
Retinal Dystrophy
Mutations of genes encoding various retina-specific proteins are known to cause a wide spectrum of inherited retinal dystrophies in different species. In the canine, several types of genetic retinal dystrophies have been described affecting primarily the photoreceptors and/or the retinal pigment epithelium.Retinal tissue, located inside the back of the eye, contains specialized cells called photoreceptors that absorb the light focused on them by the eye’s lens, and converts that light, through a series of chemical reactions into electrical nerve signals. The nerve signals from the retina are passed by the optic nerve to the brain where they are perceived as vision. The retinal photoreceptors are specialized into rods, for vision in dim light (night vision), and cones for vision in bright light (day and color vision). With Retinal Dystrophy the abnormal development of the retina usually affects the rods initially, and then cones in later stages of the disease. This disease is very closely related to various Progressive Retinal Atrophy disorders.
The disease has been observed in the Briard breed, Cavalier King Charles Spaniels, Irish Setters, Yorkshire Terriers, Doberman Pinschers, Golden Retrievers and in the American Cocker Spaniel.
While there is no known cure for the disease, studies with laboratory animals such as mice suggest that there may be beneficial results if the animal is kept in a reduced light situation and that detection of the gene defect be accomplished as early as possible.
This disease is inherited in an autosomal recessive mode.
References:
Narfström K, Wrigstad A, Ekesten B, Nilsson SEG. 1994. Hereditary retinal dystrophy in the briard dog: Clinical and hereditary characteristics. Prog Vet Comp Ophthalmol 4: 85-92.
Veske A, Narfström K, Finckh U, Sargan DR, Nilsson SE, Gal A. 1997. Isolation of canine retinal arrestin cDNA and exclusion of three candidate genes for Swedish Briard retinal dystrophy. Curr Eye Res. 16(3):270-4.
Cats
Polycystic Kidney Diseases (Click here for more information)
Polycystic disease is a disease that shows up later in life (late onset) with enlarged kidneys and kidney dysfunction occurring between three and 10 years of age (on average at seven years of age). The condition is inherited and cysts are present from birth, but are smaller in younger animals. Cyst size can vary from less than 1 mm to greater than 1 cm in size, with older animals having larger and more numerous cysts. Problems occur when these cysts start to grow and progressively enlarge the kidney, reducing the kidney's ability to function properly. The ultimate end is kidney failure. Some of the clinical signs are depression, lack of or reduced appetite, excessive thirst, excessive urination and weight loss. There is a marked difference in when and how quickly individual cats succumb, with the possibility of this developing late enough in life that the cat can die of other causes before kidney failure. However, kidney failure is certain when the cysts can grow and cause problems. Rarely, cysts are also seen in other organs such as the liver and uterus.
This disease is most commonly seen in Persians and Exotic Shorthairs
Mucopolysaccharidoses Type VI &VI Mild
MPS VII is one of the least common forms of the mucopolysaccharidoses. The disorder is caused by deficiency of the enzyme beta-glucuronidase (GUSB). In its rarest form MPS VII causes puppies to be born with hydrops fetalis, in which extreme amounts of fluid are retained in the body. Neurological symptoms may include mild to moderate mental retardation, communicating hydrocephalus, nerve entrapment, corneal clouding, and some loss of peripheral and night vision. Other symptoms include short stature, some skeletal irregularities, joint stiffness and restricted movement, and umbilical and/or inguinal hernias.
The disease is inherited as an autosomal recessive lysosomal storage disorder.
The SNP test for this disease is directed to the gene that codes for the enzyme b-glucuronidase. Dog breeds most affected by this disorder are the German Shepard as well as many types of Mixed Breed dogs. Many cat breeds affected by Type VI & VI MILD.
References:
Ponder, K. P., Melniczek, J. R., Xu, L. et al. 2002. Therapeutic neonatal hepatic gene therapy in mucopolysaccharidosis VII dogs. Proc. Natl. Acad. Sci. USA, Vol. 99:13102–13107.
Ray J, Scarpino V, Laing C, Haskins ME. 1999. Biochemical basis of the beta-glucuronidase gene defect causing canine mucopolysaccharidosis VII. J Hered. 90(1):119-23.
