Collies share Collie Eye Anomaly (CEA) with several other breeds – it’s not just a problem for collies. CEA is more technically known as Choroidal Hypoplasia (CH). It is a recessively inherited eye disorder that causes abnormal development of the choroid - an important layer of tissue under the retina of the eye. This disease is seen most frequently in U.S. collies, but also worldwide in Rough and Smooth Collies, Border Collies, Australian Shepherds, Lancashire Heelers, and Shetland Sheepdogs. Since the choroid layer does not develop normally from the start, the primary abnormality can be diagnosed at a very young age. Regrettably, there is no treatment or cure for CEA.
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.
The OptiGen genetic test for CEA/CH provides a powerful management tool for the breeder. This genetic test can distinguish all three genetic states – normal, carrier and affected. With this information, the breeder can plan matings that avoid producing any affected dogs by always selecting one parent that is normal. The other parent can be normal, carrier or even affected, and no affected dogs will result. (See table at the end.) This breeding recommendation is a big step forward, especially for breeds and countries where frequency of CEA/CH is much lower.
All my dogs are tested clear or are clear via parentage for CEA!
TNS stands for Trapped Neutrophil Syndrome. It is an immune deficiency in Border collies. It is an inherited disorder that is very common in all populations of Border collies with more than 10% of both working and show dogs carrying the defective gene and capable of having affected puppies.
TNS is a condition where the bone marrow produces neutrophils but they are not released into the bloodstream. This results in an impaired immune system that cannot fight infections.
Symptoms are variable, many of the reported TNS puppies have been born looking normal but others have been born small.
Some puppies with TNS have been small and fine boned with narrow heads at some point but this may not be evident until approx 16 weeks.
A common first sign is a bad reaction to vaccinations with signs of fever.
Blood tests may show an abnormally low segmented neutrophil level but TNS can only be definitely diagnosed by bone marrow biopsy.
Any puppy that shows any signs of infection or failure to thrive is a possible case of TNS.
There is no cure for TNS and it appears to always be fatal eventually. Antibiotic and steroid treatment can help affected dogs live a relatively active life.
TNS is an autosomal recessive condition.
The symptoms are extremely variable and will depend on the bacteria that the pup encounters. There may also be other genes that effect the disease expression.
Some dogs do not show symptoms until later in life. Older puppies & young adult dogs diagnosed with immune system problems may have TNS so they should also be tested with the DNA test
There is no evidence that carriers of the TNS defect have increased immune problems.
All my dogs are tested clear or are clear via parentage for TNS!
Ceroid Lipofuscinosis– Border Collie
This is a lysosomal storage disease, of which there are at least 2 forms seen in dogs. It is inherited in an autosomal recessive manner, and is seen infrequently but regularly in Border collies. A defect in metabolism leads to a build up of ceroid lipofuscin within cells, including those of the brain and retina. This causes death of brain cells as they cannot function normally as this waste product continues to build up.
Affected dogs will have an acute onset of neurologic signs around the age of 2 years, with common signs including abnormal behaviour, dementia-like changes, central blindness, circling and seizures. There is no treatment available and affected dogs will die quickly. Fortunately a DNA test is now available so that breeding animals may be tested and classified as normal or carriers.
Ceroid Lipofuscinosis has been diagnosed in the UK, USA and Australia in all lines of Border collies (including British and American). The prevalence of carriers within the population in Australia has been estimated from DNA testing to be around 5%, which seems to be approximately 10 times the rate in the UK and USA. It is believed that a dog who was imported into Australia was a carrier of this disease before anyone was aware of the disease, and that virtually all Border collies now in Australia can trace their descent to this dog.
Screening for Ceroid Lipofuscinosis:
All Border Collies should undergo DNA screening prior to entering breeding programs. Any dogs displaying suggestive clinical signs should also undergo testing.
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