Koolie Genes

 

As we continue to research the Australian Koolie we learn more about the genetics of the breed.

ASAP now trading as Orivet has been instrumental in helping breeders to understand and avoid health issue from occurring through the valuable use of DNA testing/screening.
We have listed the genes we have currently identified and their impact upon the breed.

 

 

Merle Associated Diseases

Merle Ocular Dysgenesis

Pigment Associated Deafness

 

Merle Ocular Dysgenesis refers to a collection of developmental eye problems that occur in association with the gene for merle colouring.

One or more of the following eye defects may be present:

 

Microphthalmia (unusually small globe)

Eccentric (off centre) pupils Coloboma

(a “hole”) of the internal eye structures, including Iris Coloboma(hole in the iris)

Lens luxation

(lens is not formed in its correct position, or moves away from it)Cataract

Retinal dysplasia (retina not formed correctly) or retinal detachment

Persistent Pupillary Membrane

(a sheet of tissue over the front of the lens)Lack of tapetum

(the refl ective surface on the back of the eye)

 

These defects occur when a dog is homozygous for the merle gene (that is a merle x merle breeding where a pup has 2 copies of the merle gene) Breeders will often cull merle x merle pups that have too much white colouring, which is often (but not always) a sign of carrying 2 merle genes. However this does not cover all homozygous pups and “phantom” merles can also occur, where the merle colouring is not readily apparent. Hence all pups should have an eye exam at 6-8 weeks. Note that small iris colobomas may not be seen if the pupil is dilated, although these alone will not usually cause any vision problems.

 

Homozygous merle dogs that carry a lot of white colouring, especially around the head and ears, will often have hearing problems. This is because pigmented cells are required inside the ear for hearing to occur. If the specialised skin cells inside the ear are non-pigmented, the vibrations that occur when noise is detected will not be transferred into a sound “signal” to the brain. Hence white colouring around the head and ears may indicate that the skin inside the ear is also non-pigmented, and that the dog has a high chance of being deaf. Specialised hearing tests may be needed to determine the status of the dog’s hearing.

 

 

Screening Tests:

1. Breeding animals should have DNA test for the merle gene, to avoid merle to merle matings. Screen any age prior to entering breeding (e.g. at 2 year)

2. Pups can also have the DNA test for merle gene, although this will not determine if they have abnormalities associated with the double merle. Testing can be done at 6 – 8 weeks, and any that have 2 copies of the merle gene can then undergo eye examination and BAER testing.

 

 

Breeds affected:

 

Australian shepherd

Australian koolie

Staffordshire terrier

American staffordshire terrier

Chihuahua

American pit bull terrier

Border collie

Cardigan welsh corgi

Collie

Dachshund

Great dane

Old english sheepdog

Shetland sheepdog

Pomeranian

Cocker spaniel,

Catahoula leopard dog

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