CEA, or Collie Eye Anomaly, arises from a genetic mutation impacting eye development. This mutation leads to defects across multiple layers of the eye. One such manifestation is Choroidal Hypoplasia, which affects the choroid’s development or pigmentation. The choroid, situated beneath the retina, houses a network of blood vessels. In Collie’s eyes, this abnormality is the most frequently encountered within CEA, yet it’s generally the mildest form, causing minimal harm.
CEA primarily affects certain breeds, including Collies, Shetland Sheepdogs, Australian Shepherds, Border Collies, and Nova Scotia Duck Tolling Retrievers. Despite its presence, the Choroidal Hypoplasia grade in CEA tends to result in dogs that maintain regular functionality without apparent vision impairments.
Disease Information
Collie Eye Anomaly (CEA), choroidal hypoplasia, is a genetic condition present from birth and inherited in dogs. It stems from a specific DNA mutation. Typically affecting both eyes, with one eye might exhibit more pronounced symptoms.
This condition arises due to the improper development of blood vessels in the choroid, the tissue layer at the back of the eyeball. These blood vessels supply nutrients to the retina, the eye part responsible for detecting light. When they fail to develop correctly during the prenatal stage, it results in CEA.
Genetics of the Disease
Choroidal Hypoplasia, a condition characterized by a deficiency in the choroid, follows a simple recessive inheritance pattern. Interestingly, even in dogs with no apparent signs during ophthalmoscopic examination, many harbor the recessive gene for this condition. These carriers can transmit the gene to approximately half of their progeny. The manifestation of retinal lesions requires both parents to possess the gene for Choroidal Hypoplasia. Therefore, while seemingly healthy dogs might carry the gene, the development of the condition necessitates the presence of the gene in both parents.
Clear
These dogs are deemed “clear,” signifying the absence of any copies of the aberrant gene linked to the tested condition. Their probability of developing the specific condition is exceedingly low, and they are anticipated to transmit a standard gene copy to their offspring.
Essentially, being clear indicates that these dogs are not carriers of the gene responsible for the tested condition, ensuring they are at minimal risk of manifesting the ailment themselves and reinforcing the likelihood of producing healthy progeny. This designation assures prospective breeders that these dogs possess a clean genetic slate concerning the specific condition under scrutiny. It underscores their suitability for sustaining a lineage devoid of the targeted congenital anomaly.
Carrier
The dog possesses both a mutated gene and a normal gene, indicating it is a carrier for Collie Eye Anomaly (CEA) / Choroidal Hypoplasia (CH). While the likelihood of the dog developing the condition is minimal, there exists a 50% chance that it can transmit the mutant gene to its progeny.
To mitigate the risk of passing on the abnormal gene, carriers should be bred exclusively with clear dogs—those devoid of the mutant gene. This breeding strategy ensures a reduced probability of the condition manifesting in future generations, promoting the health and well-being of the canine offspring.
Affected
Collie Eye Anomaly (CEA) represents an inherited set of eye issues leading to potential vision impairment. This syndrome manifests in both eyes, but their severity might vary. Affected dogs inherit the DNA mutation associated with the syndrome, yet the abnormalities might not be immediately noticeable at birth. This aspect distinguishes it from being classified as a congenital disability strictly at the moment of birth. The condition’s onset and progression occur over time, impacting vision.
Description
The eye’s functioning involves complexity. The choroid—a network of blood vessels within a tissue layer beneath the retina—is crucial in ensuring proper light absorption and sufficient blood circulation. However, when this specific area fails to develop correctly in dogs, it triggers Collie Eye Anomaly (CEA). This genetic ailment affects not only Collies but also various other breeds.
Termed Choroidal Hypoplasia as well, this condition can severely impair vision, potentially leading to gradual vision loss over time. It underscores the criticality of understanding how the eye functions and the consequences that arise when these intricate components, like the choroid, face developmental issues in our canine companions.
Clinical Signs of CEA and CH on your Border Collie
Collie Eye Anomaly (CEA) can manifest early in a dog’s life, presenting clinical signs such as undersized eyeballs with a sunken appearance, a cloudy eye aspect, and indications of vision loss. A thorough ophthalmological examination conducted by a veterinarian can unveil lesions on the retinas, aiding in diagnosing this inherited eye condition. Dog owners must be vigilant about these symptoms, as early detection allows for proactive management and care.
DNA Testing Border Collie for CEA/CH
Genetic assessment of the NHEJ1 gene in Border Collies provides a dependable method to ascertain whether a dog carries the condition or not. Inheritance of this anomaly follows an Autosomal Recessive pattern, necessitating the reception of two mutated gene copies—one from each parent—to trigger the disease.
In the context of DNA testing for Collie Eye Anomaly (CEA) and Central Progressive Retinal Atrophy (CPRA) in Border Collies, it’s important to note that carrier dogs often do not exhibit visible disease symptoms. However, when bred with another carrier possessing the same mutation, there is a heightened risk of producing offspring affected by these genetic conditions.
When two carriers are bred together, each puppy has a 25% chance of developing CEA/CPRA and a 50% chance of inheriting one copy of the NHEJ1 gene mutation, thereby becoming a carrier without showing clinical signs. Given these probabilities, reliable genetic testing is crucial for making informed decisions about breeding practices.
Do DNA Testing Clinics Publish results?
The Kennel Club will exclusively document and make public test outcomes if the report contains the dog’s microchip or tattoo identification and its registered name or number.
Any test submissions lacking these crucial identifying details will not be logged or acknowledged by the Kennel Club.
This stringent policy ensures that all published results are adequately linked to individual dogs, maintaining accuracy and authenticity within the registry.
How to Find Out if a Potential Mate has been DNA Tested?
The Health Test Results Finder from The Kennel Club enables access to DNA test outcomes conducted within their official DNA testing programs for any dog enlisted on The Kennel Club’s Breed Register.
This tool offers transparency and accessibility to valuable information regarding the DNA test results, aiding dog owners, breeders, and enthusiasts in understanding the health status of individual dogs within the registry. It serves as a comprehensive resource, facilitating informed decisions related to breeding practices ensuring responsible and informed choices that contribute to the overall well-being and health improvement of various dog breeds registered with The Kennel Club.
Breeding Advice and What Your Dog’s Results mean
Autosomal-recessive conditions necessitate the inheritance of two copies of an abnormal gene—one from each parent—before impacting a dog’s health. This genetic pattern implies that the presence of a single copy typically doesn’t lead to the development of the condition. Instead, a dog carrying only one copy of the abnormal gene typically remains asymptomatic but can potentially pass it on to its offspring.
However, when both parents pass on this abnormal gene, the dog may inherit two copies, manifesting the associated condition. Therefore, while individual dogs carrying only one copy are generally healthy, responsible breeding practices involve avoiding mating between carriers to prevent the likelihood of their offspring inheriting two copies and developing the condition.
Other Inherited Eye Disease in Collies
Inherited eye diseases extend beyond Collie Eye Anomaly (CEA) in canines. Other conditions, such as Persistent Pupillary Membranes (PPM) and Progressive Retinal Atrophy (PRA), can also be passed down through genetics.
These conditions pose significant concerns for the vision and ocular health of dogs. Persistent Pupillary Membranes involve strands of tissue in the eye, whereas Progressive Retinal Atrophy leads to gradual retina degeneration, resulting in vision loss. These inherited ailments underscore the importance of comprehensive veterinary screenings and genetic testing in breeding practices to mitigate the risk of passing these debilitating eye conditions to future generations of dogs.
Persistent Pupillary Membranes
Persistent pupillary membranes (PPM) represent a typical stage in the embryonic growth of various species. Initially, this membrane is a cohesive layer of tissue that typically dissolves during normal development, forming the pupil.
However, at times, remnants of this tissue persist, forming strands that adhere to other parts of the eye. These attachments can interfere with the normal functioning of the eye components.
PPM consists of pigmented tissue strands originating from the iris collarette, attaching to different surfaces of the iris, lens, or cornea in various species, including canines and humans. While usually harmless, these residual strands can occasionally cause visual issues or discomfort due to their abnormal connections within the eye structure.
Progressive Retinal Atrophy
Progressive Retinal Atrophy (PRA) is a degenerative condition affecting the retina in animals, characterized by a gradual decline or atrophy of retinal tissue over time. Like our eyes adjusting to gradually decreasing light, animals with PRA may not exhibit noticeable symptoms until the condition has significantly advanced. PRA encompasses a group of inherited disorders that impact various breeds due to its subtle onset.
Sadly, there’s currently no cure for PRA. Detecting affected breeding animals becomes crucial to halt the spread of this condition within the breed. Identifying carriers helps prevent mating two pages and reduces the risk of producing offspring affected by this degenerative eye disease. Reliable screening and breeding practices are vital in mitigating the impact of PRA.
Conclusion
Collie Eye Anomaly (CEA) / Choroidal Hypoplasia (CH) are inherited eye conditions prevalent in certain dog breeds. Understanding their genetic nature and transmission is crucial. Early detection through ophthalmological examinations and reliable genetic testing is crucial in controlling and minimizing the prevalence of CEA/CH within susceptible breeds, ensuring healthier generations of dogs in the future.
