Collie eye anomaly

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Collie eye anomaly (CEA) is a congenital, inherited, bilateral eye disease of dogs, which affects the retina, choroid, and sclera. It can be a mild disease or cause blindness. CEA is caused by a simple autosomal recessive gene defect. There is no treatment.

Heredity Passing of traits to offspring from the speciess parents or ancestor

Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents. Through heredity, variations between individuals can accumulate and cause species to evolve by natural selection. The study of heredity in biology is genetics.

Eye organ that detects light and converts it into electro-chemical impulses in neurons

Eyes are organs of the visual system. They provide animals with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

Dog domestic animal

The domestic dog is a member of the genus Canis (canines), which forms part of the wolf-like canids, and is the most widely abundant terrestrial carnivore. The dog and the extant gray wolf are sister taxa as modern wolves are not closely related to the wolves that were first domesticated, which implies that the direct ancestor of the dog is extinct. The dog was the first species to be domesticated and has been selectively bred over millennia for various behaviors, sensory capabilities, and physical attributes.

Contents

Affected breeds

It is known to occur in Scotch Collies (smooth and rough collies), Shetland Sheepdogs, Australian Shepherds, Border Collies, Lancashire Heelers, [1] and Nova Scotia Duck Tolling Retrievers. [2] Frequency is high in Collies and Shetland Sheepdogs, and low in Border Collies [3] and NSDTRs. [2] In the United States, incidence in the genotype of collies has been estimated to be as high as 95 percent, with a phenotypic incidence of 80 to 85 percent. [4]

The Scotch Collie is a landrace breed of dog which originated from the highland regions of Scotland. The breed consisted of both the long-haired Collie and the short-haired Collie. It is generally believed to have descended from a variety of ancient herding dogs, some dating back to the Roman occupation, which may have included Roman Cattle Dogs, Native Celtic Dogs and Viking Herding Spitzes. Other ancestors include the Gordon and Irish Setters.

Smooth Collie Dog breed

The Smooth Collie is a breed of dog developed originally for herding. It is a short-coated version of the Rough Collie of Lassie fame. Some breed organisations consider the smooth-coat and rough-coat dogs to be variations of the same breed.

Rough Collie Dog breed

The Rough Collie is a long-coated dog breed of medium to large size that, in its original form, was a type of collie used and bred for herding sheep in Scotland. Originating in the 1800s, the breed is now well known through the works of author Albert Payson Terhune, beginning with books about Lad, and through Lassie novels, movies, and television shows. Rough Collies generally come in shades of sable and white, blue merle, tri-colored, and white. The breed has a distinctive long tapered snout and tipped ears.

Pathogenesis

CEA is caused by improper development of the eye. Failure of the cells of the posterior portion of the optic vesicles to express growth hormone affects the differentiation of other cells of the eye. The choroid, especially lateral to the optic disc, is hypoplastic (underdeveloped). A coloboma, or hole, may form in or near the optic disc due to a failed closure of embryonic tissue. The degree of these abnormalities varies between individual dogs, and even between the same dog's eyes. [5] CEA is inherited as an autosomal recessive trait that has a penetrance reaching 100 percent, and has been localized to canine chromosome 37. [6]

Growth hormone peptide hormone

Growth hormone (GH) or somatotropin, also known as human growth hormone in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development. GH also stimulates production of IGF-1 and raises the concentration of glucose and free fatty acids. It is a type of mitogen which is specific only to the receptors on certain types of cells. GH is a 191-amino acid, single-chain polypeptide that is synthesized, stored and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland.

Cellular differentiation The process in which relatively unspecialized cells, e.g. embryonic or regenerative cells, acquire specialized structural and/or functional features that characterize the cells, tissues, or organs of the mature organism.

Cellular differentiation is the process where a cell changes from one cell type to another. Usually, the cell changes to a more specialized type. Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. Thus, different cells can have very different physical characteristics despite having the same genome.

Optic disc part of the eye

The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye.

Signs

The most common sign of CEA is the presence of an area of undeveloped choroid (appearing as a pale spot) lateral to the optic disc. The choroid is a collection of blood vessels supplying the retina. CEA can also cause retinal or scleral coloboma, coloboma of the optic disc, retinal detachment, or intraocular hemorrhage. It can be diagnosed by fundoscopy by the age of six or seven weeks. [3] Severe cases may be blind.

Retinal detachment Human disease

Retinal detachment is a disorder of the eye in which the retina separates from the layer underneath. Symptoms include an increase in the number of floaters, flashes of light, and worsening of the outer part of the visual field. This may be described as a curtain over part of the field of vision. In about 7% of cases both eyes are affected. Without treatment permanent loss of vision may occur.

Breeding and testing

Controversies exist around eliminating this disorder from breeding Collies. Some veterinarians advocate only breeding dogs with no evidence of disease, but this would eliminate a large portion of potential breeding stock. Because of this, others recommend only breeding mildly affected dogs, but this would never completely eradicate the condition. Also, mild cases of choroidal hypoplasia may become pigmented and therefore undiagnosable by the age of three to seven months. If puppies are not checked for CEA before this happens, they may be mistaken for normal and bred as such. Checking for CEA by seven weeks of age can eliminate this possibility. Diagnosis is also difficult in dogs with coats of dilute color because lack of pigment in the choroid of these animals can be confused with choroidal hypoplasia. Also, because of the lack of choroidal pigment, mild choroidal hypoplasia is difficult to see, and therefore cases of CEA may be missed. [3]

Veterinarian professional who treats disease, disorder, and injury in animals

A veterinarian (vet), also known as a veterinary surgeon or veterinary physician, is a professional who practices veterinary medicine by treating diseases, disorders, and injuries in non-human animals.

Coat (dog) hair that covers its body

The coat of the domestic dog refers to the hair that covers its body. A dog's coat may be a double coat, made up of a soft undercoat and a tougher topcoat, or a single coat, which lacks an undercoat. Double coats have a top coat, made of stiff hairs to help repel water and shield from dirt, and an undercoat to serve as insulation. The terms fur and hair are often used interchangeably when describing a dog's coat, however in general, a double coat, e.g., like that of the Newfoundland and most mountain dogs, is referred to as a fur coat, while a single coat, like that of the Poodle, is referred to as a hair coat.

Until recently, the only way to know if a dog was a carrier was for it to produce an affected puppy. However, a genetic test for CEA became available at the beginning of 2005, developed by the Baker Institute for Animal Health, Cornell University, and administered through OptiGen. [7] The test can determine whether a dog is affected, a carrier, or clear, and is therefore a useful tool in determining a particular dog's suitability for breeding.

Asymptomatic carrier pathogen carrier without symptoms

An asymptomatic carrier is a person or other organism that has become infected with a pathogen, but that displays no signs or symptoms.

Cornell University Private Ivy League research university in Upstate New York

Cornell University is a private and statutory Ivy League research university in Ithaca, New York. Founded in 1865 by Ezra Cornell and Andrew Dickson White, the university was intended to teach and make contributions in all fields of knowledge—from the classics to the sciences, and from the theoretical to the applied. These ideals, unconventional for the time, are captured in Cornell's founding principle, a popular 1868 Ezra Cornell quotation: "I would found an institution where any person can find instruction in any study."

Related Research Articles

American Kennel Club umbrella organization

The American Kennel Club (AKC) is a registry of purebred dog pedigrees in the United States. In addition to maintaining its pedigree registry, this kennel club also promotes and sanctions events for purebred dogs, including the Westminster Kennel Club Dog Show, an annual event which predates the official forming of the AKC, the National Dog Show and the AKC National Championship sponsored by Royal Canin, formerly the AKC/Eukanuba National Championship. Unlike most other countries' kennels clubs, the AKC is not part of the Fédération Cynologique Internationale.

Border Collie Dog breed

The Border Collie is a working and herding dog breed developed in the Scottish borders for herding livestock, especially sheep. It was specifically bred for intelligence and obedience.

Shetland Sheepdog Dog breed

The Shetland Sheepdog, often known as the Sheltie, is a breed of herding dog that originated in the Shetland Islands of Scotland. The original name was Shetland Collie, but this caused controversy among the Rough Collie breeders of the time, so the breed's name was formally changed. This hard-working small dog is intelligent, vocal, excitable and willing to please. They are incredibly loyal to their owners to the point where they are often referred to as "shadows" due to their attachment to family. This breed was formally recognized by The Kennel Club (UK) in 1909.

Labradoodle Dog breed

A Labradoodle is a crossbreed dog created by crossing the Labrador retriever and the Standard, Miniature, or Toy poodle. The term first appeared in 1955, but was not initially popular. Contrary to popular belief Labradoodles are not hypoallergenic; nevertheless it is a perceived quality that many look for in this type of crossbreed.

Australian Shepherd Shepherding dog breed from the USA

The Australian Shepherd, often known simply as the "Aussie", is a medium-sized breed of dog that was, despite its name, developed on ranches in the United States during the 19th century. There is disagreement regarding the exact history of the breed prior to its arrival in the United States, and thus no official consensus on the origin of its name or association with Australia.

Choroid vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera

The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissues, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye, while in the outlying areas it narrows to 0.1 mm. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.

Nova Scotia Duck Tolling Retriever Dog breed

The Nova Scotia Duck Tolling Retriever is a medium-sized gundog bred primarily for hunting. It is often referred to as a "toller". It is the smallest of the retrievers, and is often mistaken for a small Golden Retriever. Tollers are known to be intelligent, easy to please, alert, and high-energy dogs. The name "toller" is derived from their ability to lure waterfowl within gunshot range. The breed originated in Yarmouth County, Nova Scotia, Canada. The American Kennel Club ranks the toller as the 87th most popular dog breed.

Merle (dog coat) pattern in a dogs coat

Merle is a pattern in a dog's coat. Merle comes in different colors and patterns. The merle gene creates mottled patches of color in a solid or piebald coat, blue or odd-colored eyes, and can affect skin pigment as well. Health issues are more typical and more severe when two merles are bred together, so it is recommended that a merle be bred to a dog with a solid coat color only.

Coloboma eye disease characterized by missing pieces of tissue in structures that form the eye, such as the iris, retina, choroid or optic disc

A coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is present during early stages of prenatal development, fails to close up completely before a child is born.

ICD-10 is an international statistical classification used in health care and related industries.

Progressive retinal atrophy (PRA) is a group of genetic diseases seen in certain breeds of dogs and, more rarely, cats. Similar to retinitis pigmentosa in humans, it is characterized by the bilateral degeneration of the retina, causing progressive vision loss culminating in blindness. The condition in nearly all breeds is inherited as an autosomal recessive trait, with the exception of the Siberian Husky and the Bullmastiff. There is no treatment.

International Sheep Dog Society (ISDS) was formed with the intention of increasing interest in securing the better management of livestock by improving the shepherd's dog. This remains the intention today. Without a good working dog, the shepherd's work on both the hills and the lowlands would be impossible. It seeks to achieve this by, amongst other things, managing the registration of dogs in its stud book.

Papillorenal syndrome autosomal dominant disease characterized by optic nerve coloboma and renal disease that has material basis in heterozygous mutation in the PAX2 gene on chromosome 10q24

Papillorenal syndrome, is an autosomal dominant genetic disorder marked by underdevelopment (hypoplasia) of the kidney and colobomas of the optic nerve.

Welsh Sheepdog Dog breed

The Welsh Sheepdog is a landrace of herding dog from Wales. Some people incorrectly call a Welsh Sheepdog a Welsh Collie - usually 'Welsh Collie' is used for a cross between a Welsh Sheepdog and a Border Collie, who is often a milder dog and easier to manage than the pure breed.

Choroidal neovascularization

Choroidal neovascularization (CNV) is the creation of new blood vessels in the choroid layer of the eye. Choroidal neovascularization is a common cause of neovascular degenerative maculopathy commonly exacerbated by extreme myopia, malignant myopic degeneration, or age-related developments.

Coloboma of optic nerve

Coloboma of optic nerve, is a rare defect of the optic nerve that causes moderate to severe visual field defects.

Exercise-induced collapse (EIC) is a genetic syndrome, predominantly occurring in mixed breed dogs related to several retriever breeds as well as purebred Labrador Retrievers but also seen in Chesapeake Bay Retrievers and Curly Coated Retrievers, Boykin Spaniels, Cocker spaniels, German wire-haired pointers, Old English Sheepdogs, Bouvier des Flandres, Pembroke Welsh Corgis and Clumber Spaniels.

References

  1. ↑ "Inherited Retinopathies". The Merck Veterinary Manual. 2006. Retrieved 2007-03-19.
  2. 1 2 "Nova Scotia Duck Tolling Retriever Club (USA)". Collie Eye Anomaly Discovered In The Nova Scotia Duck Tolling Retriever. Archived from the original on September 27, 2007. Retrieved 2006-05-26.
  3. 1 2 3 Gelatt, Kirk N., ed. (1999). Veterinary Ophthalmology (3rd ed.). Lippincott, Williams & Wilkins. ISBN   0-683-30076-8.
  4. ↑ Gilger, Brian C. (2006). "Diagnosis and treatment of ocular fundus disorders of geriatric dogs" (PDF). Proceedings of the North American Veterinary Conference. Archived from the original (PDF) on 2007-09-29. Retrieved 2007-03-19.
  5. ↑ Bedford, Peter (2006). "Hereditary Retinal Diseases" (PDF). Proceedings of the 31st World Congress of the World Small Animal Veterinary Association. Retrieved 2007-03-19.
  6. ↑ Lowe J, Kukekova A, Kirkness E, Langlois M, Aguirre G, Acland G, Ostrander E (2003). "Linkage mapping of the primary disease locus for collie eye anomaly". Genomics. 82 (1): 86–95. doi:10.1016/S0888-7543(03)00078-8. PMID   12809679.
  7. ↑ "American Border Collie Association". Health and Genetics of Border Collies - A Breeder and Buyer's Guide. Archived from the original on 2006-07-15. Retrieved 2006-07-28.
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