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Please read this if you are a rat terrier owner. This is important to all rat terrier owners and very critical if you are a breeder. Only recently we became aware that some of our rat terriers carried a genetic disease called Primary Lens Luxation (PLL). A few of our puppy owners contacted us because their rat terrier had developed glaucoma. While it was upsetting to learn that some of our dogs carried PLL, I am very grateful that I was made aware of the problem. If they hadn't contacted me I wouldn't have known there was an issue since none of my own dogs have ever developed glaucoma. That is why it is so important to notify your dog's breeder if an issue comes up. Even if you aren't sure it's genetic, it is still a good idea, since issues in a given bloodline can be traced if they are reported. If a rat terrier you got from us develops glaucoma please let us know. It could help us identify other dogs that may be at risk. If your dog comes from our lines, please let us know the test results if you get your rat terrier tested. If you are wondering if your rat terrier might be at risk for developing PLL please contact us. We might be able to tell you. We are now testing all our rat terrier breeding stock. We also know the status of a few of the dogs in our dog's pedigrees. Obviously all litters from here on out will be "safe" matings. Below we have compiled information from around the web that is very useful. Here is a link to OFA's website where the PLL test can be ordered. Order OFA PLL test What is PLL? "Lens luxation is the dislocation or displacement of the lens within the eye. The lens is the clear structure in the eye, consisting of two rounded or convex surfaces, that focuses light rays to form an image onto the retina. Normally the lens is suspended between the iris (the colored portion of the eye) and the vitreous (the clear gel in the back of the eye), and is held in place by small fibers called zonules or suspensory ligaments. Should the zonules break, the lens can either become partially dislocated (subluxated) from its normal position or completely dislocated (luxated). When the lens detaches and falls forward into the anterior chamber in front of the pupil, it is called an anterior luxation. When it falls back into the rear portion of the eye, it is called a posterior luxation."
"Primary Primary lens luxation is an inherited disorder in which the
zonules or suspensory fibers degenerate. The condition occurs mainly
in the terrier breeds, namely the Parson Russell terrier, Tibetan
terrier, smooth fox terrier and rat terrier. Primary luxations are
also seen in the border collie, the Australian cattle dog (blue
heeler), and sporadically in other breeds. Although the underlying
reasons for the lens luxation are not well understood, inflammation
or a defect in the zonules may play a role. With primary lens
luxations, both eyes are prone to dislocation of the lens. "
Please check out these links for more info: A DNA Test for Primary Lens Luxation is Available NOW!!
Until October 15, 2009 there was NO test for PLL. Breeders were having to breed in the dark. But NOW, we have the tool we need to eliminate this disease from our bloodlines. The University of Missouri, College of Veterinary Medicine through the partnership of OFA (Orthopedic Foundation for Animals), now has a DNA test for this mutation. The DNA test can determine a dogs PLL status as: AFFECTED- "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”. CARRIER- "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 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”. NORMAL- "A dog testing NORMAL has 2 normal copies of the gene, is not at risk for developing PLL, and can only pass a normal copy of the gene to any offspring." Dogs that have been determined as carriers and normal can be bred safely:
Breeding Strategies *Clear/Normal; "This finding indicates that the gene is not present in your dog. Therefore, when used for breeding, a Clear dog will not pass on the disease gene." Carrier: "This finding indicates that one copy of the disease gene is present in your dog, but that it will not exhibit disease symptoms. Carriers will not have medical problems as a result. Dogs with Carrier status can be enjoyed without the fear of developing medical problems but will pass on the disease gene 50% of the time." Affected: "This finding indicates that two copies of the disease gene are present in the dog. Unfortunately, the dog will be medically affected by the disease. Appropriate treatment should be pursued by consulting a veterinarian." * Please Note: Some sites and some breeders use the word Normal or Clear. Both these words mean the same thing. It means that the dog in question is NOT a Carrier nor is it Affected. Sometimes you will see the wording "Cleared By Parentage" or "CBP". This means both sire and dam are proven Normal/Clear and that pair bred together can never produce an affected or a carrier.
Helpful Canine Breeding Chart
SOURCE: VetGen Breeding Strategies Breeding Advice
"Our research has also demonstrated that the frequency of the PLL
mutation is extremely high in the PLL-affected breeds that we have
studied in depth. This means that allowing only CLEAR dogs to breed
could have a devastating effect on breed diversity and substantially
increase the likelihood of new inherited diseases emerging.
Therefore, we strongly advise breeders to consider all their dogs
for breeding, regardless of their PLL genotype. GENETICALLY AFFECTED
and CARRIER dogs can be bred with, but should only be bred to DNA
tested, CLEAR dogs. All puppies from any litter that has at least
one CARRIER parent should be DNA tested, so that the CARRIERS can be
identified and followed clinically throughout their lives. This
practise should be followed for at least one or two generations, to
allow the PLL mutation to be slowly eliminated from the population
without severely reducing the genetic diversity of breeds at risk."
Here is a link to OFA's website where the PLL test can be ordered: Order OFA PLL test
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