Cerebellar Abiotrophy in Working Kelpies (Also known as CA)
What is CA?
CA has at least three distinct genetic causes, with some first recognised by breeders in the 1970s, in Australian Working Kelpies. The majority are of two presentations: early-onset and late-onset. A third group of dogs, all from one family, present with early-onset CA, but were genetically distinct from the other early-onset cases.
CA is classed as an autosomal-recessive genetic neurological disease, in which the cerebellum (part of the brain) degenerates. CA usually involves a degeneration or loss of Purkinje neutrons, and a variable loss of granule cells.
The disease process itself is well known, as it occurs in humans and other animals. At least four attempts since the early 1990s have been made by different research teams to develop a test and identify the causative genes. However due to the genetic complexity, some marker tests have only recently been found; we do not know everything there is to know. What we do know at the moment, is that a dog will be one of the following:
Affected. This means that the dog has signs of CA, and carries two copies of the gene. They will have inherited one copy each from either one affected parent and one carrier parent, or from two carrier parents.
Carrier. This means that the dog has no signs of CA, but carries one copy of the gene. They will have inherited one copy of the gene from one parent who is either a carrier or affected. If a carrier is bred with another carrier, on average, 25% of the pups will be affected, although in some carrier to carrier matings there may be no affected pups and others may have quite a few.
Clear. This means that the dog has no signs of CA, and carries no copies of the gene. A clear dog can be bred with a carrier dog, and will produce clear or carrier progeny, but not affected pups.
The BATWK database will prove invaluable for helping to significantly reduce the number of affected pups produced in the UK. There is the ability to record the CA 'status' of your dog, and to check for the 'status' of other dogs registered with BATWK. This will ensure that a record is kept of which genetic lines contain CA, and will help prospective Kelpie owners pick a pup free from CA.
There is a private support group for anyone wishing to find out more information about CA on facebook, you can access it here. We are encouraging all of those that test for the disease through BATWK to share their results on this page, to help improve clarity of which dogs carry which genes. All results shared within the group, will not be shared elsewhere.
Please see the diagram below illustrating how CA is inherited and passed through generations.
What does CA mean for my dog?
Dogs that are actually affected with CA (i.e. carry two CA genes) can show head tremors, problems with balance and exaggerated or erratic leg movements. These signs can vary significantly between individual dogs, and the types of CA. Dogs with late-onset CA tend to have severe and progressive signs; early-onset CA dogs can sometimes have a good quality of life, as companion or agility dogs, but there is no cure no matter how mild the case. Severely affected dogs are usually euthanised for humane reasons as there is no treatment currently available.
At present, three variants of CA have been identified, but there may be more. A dog can carry genes for more than one variant. These different variants of CA, appear at different times and have different severity, which are briefly summarised below by the current marker tests:
VMP1. This marker is associated with later onset CA where signs start anywhere from three months to well over a year old. This marker is excellent at predicting CA. Mating two carriers for this marker should not be done.
LINGO3. This marker is associated with early onset CA, where signs start at 4-16 weeks of age. This marker may predict about half the cases of the early-onset CA; a more accurate marker is being investigated. Mating two carriers for this marker should not be done.
NUP153. This CA marker was identified from a single litter of affected pups. In this litter pups showed signs of CA while they were very young, at around 4 weeks of age. Currently, this test is only recommended for predicting CA in dogs directly related to the family which was initially researched.
How do I check if my dog carries any markers of CA genes?
There is currently only one lab in the world which offers testing for CA, Dog Breeding Science, based in Australia. More information on how to order and purchase the test can be found on the Dog Breeding Science website here. If you wish to test through BATWK, use the instructions found here.
It is important to be mindful that the LINGO3 marker test might not detect all of the affected and carrier dogs of this early-onset type (which is not a reason to not test!), but with every dog that is tested, the tests will become more accurate and refined.
What does it mean if my dog is a carrier?
This is a hard question to answer, and one that different breeders have very different opinions on. The general consensus at BATWK is that not breeding from exceptional working dogs who are carriers, will unnecessarily restrict the gene pool of Kelpies in the UK and preventing affected pups can still be achieved when mating exceptional carrier dogs. In the UK we already have a relatively small gene pool of working kelpies. Whilst we at BATWK are working hard to change this, we need to be careful to not eliminate the best working traits from the gene pool we currently have.
Having said this, a carrier should NEVER be bred with another carrier. The aim is to produce healthy dogs that are fit to live a fulfilling life, for both the owner and dog. We recommend that if a carrier with exceptional working ability is bred to a clear dog, all pups are tested from the litter, so they can be sold to prospective owners knowing what their CA status is. Or at least, sold with the request that they are not bred from unless their CA status is confirmed.
Be aware that matings of even clear to clear for the LINGO3 marker may in some cases produce early-onset CA affected pups. We have hopes that a more accurate test will become available sooner rather than later.
For those of you looking to purchase a pup with good working ability, with no intention to breed from it, there is no issue with purchasing a carrier at all. If you purchase a pup with the intention to breed from it, it may be wise to let the breeder know this, so they may be able to help you select a pup which is not a carrier, so there is less expense for yourself down the line, and we speed up the elimination of this disease.