Toy Aussie Genetic testing

MDR1 is the abbreviated name of a gene called Multi-Drug Resistance 1.  A mutation of this gene causes sensitivity to Ivermectin and a number of other drugs.  Dogs with the mutation will react to those drugs.  

Whether a dog reacts depends on the dosage of the drug.  A dog may not react to very low doses, as with the amount of Ivermectin found in heart worm products.  Typical doses of a variety of medications will cause reactions in dogs with two copies of the mutation, but some drugs – most notably several chemotherapy agents – can cause reactions in dogs with only one.  Dogs with this mutation have a transport defect. The drug goes in to their brains, fails to be transported out, and builds up to toxic levels.  This causes serious neurological problems including seizures and sometimes death. 

The test report will provide you with the genotype for your dog, generally listed as Normal/Normal, Normal/Mutant or Mutant/Mutant.  Dogs with even one copy of the mutation should be considered sensitive to listed drugs. 

 Breeders should consider the mutation to be a fault, but not a disqualifying one.   

Collie Eye Anomaly (CEA) is a sometimes blinding congenital inherited eye disease.  All dogs with CEA have bilateral choroidal hypoplasia (CH), also called chorioretinal dysplasia, a thinning of the vascular tissue in the back of the eye which does not significantly impair vision.  Some dogs will also have optic nerve coloboma, in which the nerve tissue is not fully developed where the optic nerve enters the back of the eye.  A few will have retinal detachment.  Both of these more serious defects can be blinding.  CEA is present at birth and does not progress, so there is no worry that an affected puppy will get worse as it gets older.  

Hereditary Cataracts (HC) are one of the Australian Shepherd’s most common hereditary problems and easily the breed’s most common inherited eye disease.   The lens has three layers of tissue: The nucleus at its core, an outer layer called the cortex, and a skin referred to as the capsule. The front and back are termed anterior and posterior, respectively. The outer rim of the lens is called the equator. Each lens also has anterior and posterior suture lines where the tissue came together during development. 

 There are several genetically distinct forms of Progressive Retinal Atrophy in dogs.  PRA is a gradual degeneration of the retinal tissue.  The form found in Australian Shepherds is Progressive Rod Cone Degeneration (PRCD).  Age of onset is usually in the prime of life.  The first things an owner might notice is night-blindness.   The disease progresses, over months or years, until the dog is blind.  The disease is caused by a recessive gene mutation. 

Any Aussie diagnosed with PRA should also have the PRCD DNA test to confirm the diagnosis.  Affected dogs should not be bred.  Carriers should be bred only to mates that have tested clear and all offspring which will be used for breeding will need to be tested.  Preference should be given to non-carrier offspring.  Carriers should not be used at public stud.