technically exists in about 30% of Glens, although it does not appear to cause symptoms in
the dogs, probably because of their low-to-the-ground structure and their massive muscling
in the loin area.
More care must be taken with the front end. As a chondrodysplastic
breed, Glens are supposed to have a crooked front with front feet turned out.
This structure leaves the growing Glen puppy susceptible to growth plate fractures
(premature closure of the distal ulna), so going down steep stairs, jumping out of cars or
off couches or beds should be discouraged until the growth plates have closed, around one
year of age.
If a puppy starts limping on a front leg (commonly between four and ten
months of age), immediately enforce crate rest and curtail any activity that leads to
excessive force on the joints. Your vet may want to follow up with x-rays. Careful
attention during this time period may be sufficient to avoid surgery that is sometimes
The Glen has a very limited gene pool and a history of inbreeding, which
increases the risk of inheriting genetic diseases. Two such inherited diseases have now been identifed in Glens.
PRA – Progressive Retinal Atrophy
PRA was confirmed in Glens in 1996. It took more than a decade, but fortunately we now have a simple blood test for the genetic mutation that causes PRA in Glens. Dogs affected with this inherited disease, known as crd3, usually develop late-onset progressive blindness.
Glen breeders now have the tools to avoid ever again creating a
blind dog. As long as at least one parent in a mating has two normal/clear genes,
none of the puppies will ever go blind from crd3. Breeders MUST make use of the
blood test for their breeding stock to accomplish this!
It is unnecessary, and probably unwise for the health of our gene pool, to
insist that both parents always have two normal/clear genes, since over 50% of Glens are
associated with the mutation, either as carriers (the majority) or affecteds. We
simply cannot afford to throw away half of our gene pool and still expect to maintain
desired characteristics and health of our breed.
Statistically, by always ensuring that at least one parent is
normal/clear, we can eliminate the disease in about five generations while still
maintaining 95% of our desired breed characteristics and genetic diversity. This
could take at least a couple of decades, but if we are patient and careful, we will still
have a genuine Glen of Imaal Terrier breed to work with.
DM – Degenerative Myelopathy
DM was identified in Glen of Imaal Terriers in 2019. DM is the canine equivalent of amyotrophic lateral sclerosis (ALS) — Lou Gehrig’s disease, in humans. It affects the dog late in life, there is no cure, and unlike PRA, it is a fatal disease. However, like PRA, we have an existing genetic testing tool (a simple, inexpensive cheek swab) which breeders can use to ensure they never create another puppy at risk of developing the disease. The breeding guidelines for using this gene test are the same as for crd3, the Glen form of PRA.
All Glen breeders should be utilizing this genetic tool, similarly to the crd3 gene test, to prevent creating puppies at risk for DM. Once we are testing broadly, we will have a better idea how widespread the problem gene is in our breed. I personally think it is not yet widespread, and that by using gene testing wisely, we can prevent it becoming a pervasive problem in our small breed.
To see video of a couple of Glens affected with DM paralysis, please visit the GlenHealth website.
Breeding Recommendations when a breed has a small gene pool like the Glen:
To minimize the serious and detrimental effects of genetic bottlenecking,
it is recommended that breeders pay attention not only to pedigrees, but also to
inbreeding coefficients. It is strongly recommended to have inbreeding coefficients
below 25%; I personally strive for less than 20%, although this is not easy.
An excellent resource for depth of pedigree and inbreeding coefficient information is the International Glen Database.
This volunteer, international database for Glen of Imaal Terriers was widely used by the
university researchers in both Europe and America while pursuing our PRA problem.
Glen breeders can sign up for a
password to access the database, which includes many ancestor pictures as well as reported gene status of Glens that have been tested for genetic diseases.