Miniature Bull Terriers are generally quite healthy, but there are eye, skin, kidney, and heart problems in some dogs.
Primary Lens Luxation is an eye problem well known in miniature bull terriers. The lens is held in place in the eye by fibers known as zonules. If these zonules stretch or break, the lens can fall out of place, or luxate. When this happens it often requires immediate veterinary attention to remove the displaced lens and prevent painful secondary glaucoma, and sometimes loss of vision.
Testing and Inheritance of PLL
From pedigree studies done previously, there has been general agreement that PLL is inherited as a simple recessive trait. This means that a dog needs 2 mutated, or “bad” copies of the gene to show the disease. With the PLL mutation identified, and the research groups able to compare notes on the dogs used in the study, it has become apparent that there are some exceptions. While the vast majority of dogs with PLL have tested AFFECTED, as small percentage of the dogs that test CARRIER are also at risk of developing PLL. Owners and breeders should be aware of this and understand the implications of the test results so that they can make well-informed decisions for the future of individual dogs, and the breed as a whole.
Dogs that test AFFECTED have 2 mutated copies of the gene. The vast majority of these dogs will luxate at 4-8yrs of age, the typical age of onset for PLL. There were a few dogs in the study group that tested as AFFECTED but did not luxate until after 8 yrs of age, and some dogs testing AFFECTED have died from other causes without luxating. A search of published veterinary literature revealed that about 10% of the dogs reported to be clinically affected with PLL had onset of symptoms after 8 yrs of age. Because of this, the test results will say “AFFECTED/HIGH RISK”.
As stated earlier, dogs testing CARRIER are at a slight risk of developing PLL. Carriers have one normal and one mutated copy of the gene. They could pass either the normal copy or the mutated copy on to their offspring. Because there were a very few cases of dogs in the research groups testing CARRIER who did appear to have PLL, the test results will say “CARRIER/LOW RISK”.