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.


Update: As of 2017 all of our breeding dogs are PLL Clear so PLL is no longer an concern for any of the puppies that come from us. If you are buying from another breeder always be sure to find out what the puppy's PLL status is. 


Only recently (this was written in 2010) 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 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:

Canine Lens Luxation Basics

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
Autosomal Recessive Diseases

*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
Autosomal Recessive Diseases

"The chart provided below outlines the implications of various breeding pair combinations. Remember, it is always best to breed "Clear to Clear". If followed by all breeders, these strategies will ensure a significant reduction in the frequency of the targeted disease gene in future generations of dogs. However, to maintain a large enough pool of good breeding stock, it may be necessary for some breeders to breed "Clear" to "Carriers" (see below)."


Clear Male

Carrier Male

Affected Male

Clear Female

100% Clear

50/50 Carrier/Clear

100% Carrier

Carrier Female

50/50 Carrier/Clear

25/50/25 Clr./Carr./Affctd.

50/50 Carrier/Affected

Affected Female

100% Carrier

50/50 Carrier/Affected

100% Affected


"Ideal Breeding Pair - Puppies will not have the disease gene (neither as Carrier nor as Affected)."

Breeding Is Safe - "No Affected puppies will be produced. However, some or all puppies will be Carriers. Accordingly, it is recommended that Carrier dogs which are desirable for breeding be bred with Clear dogs in the future, which will produce 50% carrier and 50% clear animals, to further reduce the disease gene frequency. These offspring should be tested for this defective gene, and if possible, only the clear animals in this generation should be used."

High Risk Breeding - Some puppies are likely to be Carriers and some puppies are likely to be Affected. Even though it is possible that there will be some clear puppies when breeding "Carrier to Carrier", in general, neither this type of breeding pair nor "Carrier to Affected" are recommended for breeding.

Breeding Not Recommended - "All puppies will be genetically and medically affected."

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."
Source:Animal Health Trust

Here is a link to OFA's website where the PLL test can be ordered:  Order OFA PLL test



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